Journal articles on the topic 'MITgcm model'
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Völpel, Rike, André Paul, Annegret Krandick, Stefan Mulitza, and Michael Schulz. "Stable water isotopes in the MITgcm." Geoscientific Model Development 10, no. 8 (August 25, 2017): 3125–44. http://dx.doi.org/10.5194/gmd-10-3125-2017.
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Abstract. We present the first results of the implementation of stable water isotopes in the Massachusetts Institute of Technology general circulation model (MITgcm). The model is forced with the isotopic content of precipitation and water vapor from an atmospheric general circulation model (NCAR IsoCAM), while the fractionation during evaporation is treated explicitly in the MITgcm. Results of the equilibrium simulation under pre-industrial conditions are compared to observational data and measurements of plankton tow records (the oxygen isotopic composition of planktic foraminiferal calcite). The broad patterns and magnitude of the stable water isotopes in annual mean seawater are well captured in the model, both at the sea surface as well as in the deep ocean. However, the surface water in the Arctic Ocean is not depleted enough, due to the absence of highly depleted precipitation and snowfall. A model–data mismatch is also recognizable in the isotopic composition of the seawater–salinity relationship in midlatitudes that is mainly caused by the coarse grid resolution. Deep-ocean characteristics of the vertical water mass distribution in the Atlantic Ocean closely resemble observational data. The reconstructed δ18Oc at the sea surface shows a good agreement with measurements. However, the model–data fit is weaker when individual species are considered and deviations are most likely attributable to the habitat depth of the foraminifera. Overall, the newly developed stable water isotope package opens wide prospects for long-term simulations in a paleoclimatic context.
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Sun, Shantong, Ian Eisenman, Laure Zanna, and Andrew L. Stewart. "Surface Constraints on the Depth of the Atlantic Meridional Overturning Circulation: Southern Ocean versus North Atlantic." Journal of Climate 33, no. 8 (April 15, 2020): 3125–49. http://dx.doi.org/10.1175/jcli-d-19-0546.1.
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AbstractPaleoclimate proxy evidence suggests that the Atlantic meridional overturning circulation (AMOC) was about 1000 m shallower at the Last Glacial Maximum (LGM) compared to the present. Yet it remains unresolved what caused this glacial shoaling of the AMOC, and many climate models instead simulate a deeper AMOC under LGM forcing. While some studies suggest that Southern Ocean surface buoyancy forcing controls the AMOC depth, others have suggested alternatively that North Atlantic surface forcing or interior diabatic mixing plays the dominant role. To investigate the key processes that set the AMOC depth, here we carry out a number of MITgcm ocean-only simulations with surface forcing fields specified from the simulation results of three coupled climate models that span much of the range of glacial AMOC depth changes in phase 3 of the Paleoclimate Model Intercomparison Project (PMIP3). We find that the MITgcm simulations successfully reproduce the changes in AMOC depth between glacial and modern conditions simulated in these three PMIP3 models. By varying the restoring time scale in the surface forcing, we show that the AMOC depth is more strongly constrained by the surface density field than the surface buoyancy flux field. Based on these results, we propose a mechanism by which the surface density fields in the high latitudes of both hemispheres are connected to the AMOC depth. We illustrate the mechanism using MITgcm simulations with idealized surface forcing perturbations as well as an idealized conceptual geometric model. These results suggest that the AMOC depth is largely determined by the surface density fields in both the North Atlantic and the Southern Ocean.
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Zhai, Xiaoming, Helen L. Johnson, and David P. Marshall. "A Model of Atlantic Heat Content and Sea Level Change in Response to Thermohaline Forcing." Journal of Climate 24, no. 21 (November 1, 2011): 5619–32. http://dx.doi.org/10.1175/jcli-d-10-05007.1.
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Abstract The response of ocean heat content in the Atlantic to variability in the meridional overturning circulation (MOC) at high latitudes is investigated using a reduced-gravity model and the Massachusetts Institute of Technology (MIT) general circulation model (MITgcm). Consistent with theoretical predictions, the zonal-mean heat content anomalies are confined to low latitudes when the high-latitude MOC changes rapidly, but extends to mid- and high latitudes when the high-latitude MOC varies on decadal or multidecadal time scales. This low-pass-filtering effect of the mid- and high latitudes on zonal-mean heat content anomalies, termed here the “Rossby buffer,” is shown to be associated with the ratio of Rossby wave basin-crossing time to the forcing period at high northern latitudes. Experiments using the MITgcm also reveal the importance of advective spreading of cold water in the deep ocean, which is absent in the reduced-gravity model. Implications for monitoring ocean heat content and sea level changes are discussed in the context of both models. It is found that observing global sea level variability and sea level rise using tide gauges can substantially overestimate the global-mean values.
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Safin, Artur, Damien Bouffard, Firat Ozdemir, Cintia L. Ramón, James Runnalls, Fotis Georgatos, Camille Minaudo, and Jonas Šukys. "A Bayesian data assimilation framework for lake 3D hydrodynamic models with a physics-preserving particle filtering method using SPUX-MITgcm v1." Geoscientific Model Development 15, no. 20 (October 21, 2022): 7715–30. http://dx.doi.org/10.5194/gmd-15-7715-2022.
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Abstract. We present a Bayesian inference for a three-dimensional hydrodynamic model of Lake Geneva with stochastic weather forcing and high-frequency observational datasets. This is achieved by coupling a Bayesian inference package, SPUX, with a hydrodynamics package, MITgcm, into a single framework, SPUX-MITgcm. To mitigate uncertainty in the atmospheric forcing, we use a smoothed particle Markov chain Monte Carlo method, where the intermediate model state posteriors are resampled in accordance with their respective observational likelihoods. To improve the uncertainty quantification in the particle filter, we develop a bi-directional long short-term memory (BiLSTM) neural network to estimate lake skin temperature from a history of hydrodynamic bulk temperature predictions and atmospheric data. This study analyzes the benefit and costs of such a state-of-the-art computationally expensive calibration and assimilation method for lakes.
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Ren, Shihe, Xi Liang, Qizhen Sun, Hao Yu, L. Bruno Tremblay, Bo Lin, Xiaoping Mai, et al. "A fully coupled Arctic sea-ice–ocean–atmosphere model (ArcIOAM v1.0) based on C-Coupler2: model description and preliminary results." Geoscientific Model Development 14, no. 2 (February 24, 2021): 1101–24. http://dx.doi.org/10.5194/gmd-14-1101-2021.
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Abstract. The Arctic regional coupled sea-ice–ocean–atmosphere model (ArcIOAM) has been developed to provide reliable Arctic sea ice prediction on seasonal timescales. The description and implementation of ArcIOAM and its preliminary results for the year of 2012 are presented in this paper. In the ArcIOAM configuration, the Community Coupler 2 (C-Coupler2) is used to couple the Arctic sea-ice–oceanic configuration of the MITgcm (Massachusetts Institute of Technology general circulation model) with the Arctic atmospheric configuration of the Polar WRF (Weather Research and Forecasting) model. A scalability test is performed to investigate the parallelization of the coupled model. As the first step toward reliable Arctic seasonal sea ice prediction, ArcIOAM, implemented with two-way coupling strategy along with one-way coupling strategy, is evaluated with respect to available observational data and reanalysis products for the year of 2012. A stand-alone MITgcm run with prescribed atmospheric forcing is performed for reference. From the comparison, all the experiments simulate reasonable evolution of sea ice and ocean states in the Arctic region over a 1-year simulation period. The two-way coupling has better performance in terms of sea ice extent, concentration, thickness and sea surface temperature (SST), especially in summer. This result indicates that sea-ice–ocean–atmosphere interaction plays a crucial role in controlling Arctic summertime sea ice distribution.
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Cossarini, Gianpiero, Stefano Querin, Cosimo Solidoro, Gianmaria Sannino, Paolo Lazzari, Valeria Di Biagio, and Giorgio Bolzon. "Development of BFMCOUPLER (v1.0), the coupling scheme that links the MITgcm and BFM models for ocean biogeochemistry simulations." Geoscientific Model Development 10, no. 4 (April 5, 2017): 1423–45. http://dx.doi.org/10.5194/gmd-10-1423-2017.
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Abstract. In this paper, we present a coupling scheme between the Massachusetts Institute of Technology general circulation model (MITgcm) and the Biogeochemical Flux Model (BFM). The MITgcm and BFM are widely used models for geophysical fluid dynamics and for ocean biogeochemistry, respectively, and they benefit from the support of active developers and user communities. The MITgcm is a state-of-the-art general circulation model for simulating the ocean and the atmosphere. This model is fully 3-D (including the non-hydrostatic term of momentum equations) and is characterized by a finite-volume discretization and a number of additional features enabling simulations from global (O(107) m) to local scales (O(100) m). The BFM is a biogeochemical model based on plankton functional type formulations, and it simulates the cycling of a number of constituents and nutrients within marine ecosystems. The online coupling presented in this paper is based on an open-source code, and it is characterized by a modular structure. Modularity preserves the potentials of the two models, allowing for a sustainable programming effort to handle future evolutions in the two codes. We also tested specific model options and integration schemes to balance the numerical accuracy against the computational performance. The coupling scheme allows us to solve several processes that are not considered by each of the models alone, including light attenuation parameterizations along the water column, phytoplankton and detritus sinking, external inputs, and surface and bottom fluxes. Moreover, this new coupled hydrodynamic–biogeochemical model has been configured and tested against an idealized problem (a cyclonic gyre in a mid-latitude closed basin) and a realistic case study (central part of the Mediterranean Sea in 2006–2012). The numerical results consistently reproduce the interplay of hydrodynamics and biogeochemistry in both the idealized case and Mediterranean Sea experiments. The former reproduces correctly the alternation of surface bloom and deep chlorophyll maximum dynamics driven by the seasonal cycle of winter vertical mixing and summer stratification; the latter simulates the main basin-wide and mesoscale spatial features of the physical and biochemical variables in the Mediterranean, thus demonstrating the applicability of the new coupled model to a wide range of ocean biogeochemistry problems.
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Strobach, Ehud, Andrea Molod, Donifan Barahona, Atanas Trayanov, Dimitris Menemenlis, and Gael Forget. "Earth system model parameter adjustment using a Green's functions approach." Geoscientific Model Development 15, no. 5 (March 17, 2022): 2309–24. http://dx.doi.org/10.5194/gmd-15-2309-2022.
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Abstract. We demonstrate the practicality and effectiveness of using a Green's functions estimation approach for adjusting uncertain parameters in an Earth system model (ESM). This estimation approach has previously been applied to an intermediate-complexity climate model and to individual ESM components, e.g., ocean, sea ice, or carbon cycle components. Here, the Green's functions approach is applied to a state-of-the-art ESM that comprises a global atmosphere/land configuration of the Goddard Earth Observing System (GEOS) coupled to an ocean and sea ice configuration of the Massachusetts Institute of Technology general circulation model (MITgcm). Horizontal grid spacing is approximately 110 km for GEOS and 37–110 km for MITgcm. In addition to the reference GEOS-MITgcm simulation, we carried out a series of model sensitivity experiments, in which 20 uncertain parameters are perturbed. These “control” parameters can be used to adjust sea ice, microphysics, turbulence, radiation, and surface schemes in the coupled simulation. We defined eight observational targets: sea ice fraction, net surface shortwave radiation, downward longwave radiation, near-surface temperature, sea surface temperature, sea surface salinity, and ocean temperature and salinity at 300 m. We applied the Green's functions approach to optimize the values of the 20 control parameters so as to minimize a weighted least-squares distance between the model and the eight observational targets. The new experiment with the optimized parameters resulted in a total cost reduction of 9 % relative to a simulation that had already been adjusted using other methods. The optimized experiment attained a balanced cost reduction over most of the observational targets. We also report on results from a set of sensitivity experiments that are not used in the final optimized simulation but helped explore options and guided the optimization process. These experiments include an assessment of sensitivity to the number of control parameters and to the selection of observational targets and weights in the cost function. Based on these sensitivity experiments, we selected a specific definition for the cost function. The sensitivity experiments also revealed a decreasing overall cost as the number of control variables was increased. In summary, we recommend using the Green's functions estimation approach as an additional fine-tuning step in the model development process. The method is not a replacement for modelers' experience in choosing and adjusting sensitive model parameters. Instead, it is an additional practical and effective tool for carrying out final adjustments of uncertain ESM parameters.
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Zaporozhtsev, I. F., and D. V. Moiseev. "Simulation of spatio-temporal variability of temperature in the Taganrog Bay with MITgcm model." Vestnik MGTU 20, no. 1/2 (March 2017): 231–41. http://dx.doi.org/10.21443/1560-9278-2017-20-1/2-231-241.
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Sraj, Ihab, Sarah E. Zedler, Omar M. Knio, Charles S. Jackson, and Ibrahim Hoteit. "Polynomial Chaos–Based Bayesian Inference of K-Profile Parameterization in a General Circulation Model of the Tropical Pacific." Monthly Weather Review 144, no. 12 (November 9, 2016): 4621–40. http://dx.doi.org/10.1175/mwr-d-15-0394.1.
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Abstract The authors present a polynomial chaos (PC)–based Bayesian inference method for quantifying the uncertainties of the K-profile parameterization (KPP) within the MIT general circulation model (MITgcm) of the tropical Pacific. The inference of the uncertain parameters is based on a Markov chain Monte Carlo (MCMC) scheme that utilizes a newly formulated test statistic taking into account the different components representing the structures of turbulent mixing on both daily and seasonal time scales in addition to the data quality, and filters for the effects of parameter perturbations over those as a result of changes in the wind. To avoid the prohibitive computational cost of integrating the MITgcm model at each MCMC iteration, a surrogate model for the test statistic using the PC method is built. Because of the noise in the model predictions, a basis-pursuit-denoising (BPDN) compressed sensing approach is employed to determine the PC coefficients of a representative surrogate model. The PC surrogate is then used to evaluate the test statistic in the MCMC step for sampling the posterior of the uncertain parameters. Results of the posteriors indicate good agreement with the default values for two parameters of the KPP model, namely the critical bulk and gradient Richardson numbers; while the posteriors of the remaining parameters were barely informative.
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YAMAGUCHI, Kosei, Takao YAMASHITA, Han Soo LEE, and Ryota OHSHIRO. "Numerical Experiment for Typhoon and Ocean Interaction by MITgcm-MM5 Coupling Model." PROCEEDINGS OF COASTAL ENGINEERING, JSCE 54 (2007): 336–40. http://dx.doi.org/10.2208/proce1989.54.336.
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Hoteit, I., B. Cornuelle, V. Thierry, and D. Stammer. "Impact of Resolution and Optimized ECCO Forcing on Simulations of the Tropical Pacific." Journal of Atmospheric and Oceanic Technology 25, no. 1 (January 1, 2008): 131–47. http://dx.doi.org/10.1175/2007jtecho528.1.
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Abstract The sensitivity of the dynamics of a tropical Pacific Massachusetts Institute of Technology (MIT) general circulation model (MITgcm) to the surface forcing fields and to the horizontal resolution is analyzed. During runs covering the period 1992–2002, two different sets of surface forcing boundary conditions are used, obtained 1) from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis project and 2) from the Estimating the Circulation and Climate of the Ocean (ECCO) assimilation consortium. The “ECCO forcing” is the “NCEP forcing” adjusted by a state estimation procedure using the MITgcm with a 1° × 1° global grid and the adjoint method assimilating a multivariate global ocean dataset. The skill of the model is evaluated against ocean observations available in situ and from satellites. The model domain is limited to the tropical Pacific, with open boundaries located along 26°S, 26°N, and in the Indonesian throughflow. To account for large-scale changes of the ocean circulation, the model is nested in the global time-varying ocean state provided by the ECCO consortium on a 1° grid. Increasing the spatial resolution to 1/3° and using the ECCO forcing fields significantly improves many aspects of the circulation but produces overly strong currents in the western model domain. Increasing the resolution to 1/6° does not yield further improvements of model results. Using the ECCO heat and freshwater fluxes in place of NCEP products leads to improved time-mean model skill (i.e., reduced biases) over most of the model domain, underlining the important role of adjusted heat and freshwater fluxes for improving model representations of the tropical Pacific. Combinations of ECCO and NCEP wind forcing fields can improve certain aspects of the model solutions, but neither ECCO nor NCEP winds show clear overall superiority.
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Mishra, Alok Kumar, Suneet Dwivedi, and Fabio Di Sante. "Performance of the RegCM-MITgcm Coupled Regional Model in Simulating the Indian Summer Monsoon Rainfall." Pure and Applied Geophysics 178, no. 2 (January 25, 2021): 603–17. http://dx.doi.org/10.1007/s00024-020-02648-0.
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Christie, Duncan A., Elspeth K. H. Lee, Hamish Innes, Pascal A. Noti, Benjamin Charnay, Thomas J. Fauchez, Nathan J. Mayne, et al. "CAMEMBERT: A Mini-Neptunes General Circulation Model Intercomparison, Protocol Version 1.0.A CUISINES Model Intercomparison Project." Planetary Science Journal 3, no. 11 (November 1, 2022): 261. http://dx.doi.org/10.3847/psj/ac9dfe.
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Abstract With an increased focus on the observing and modeling of mini-Neptunes, there comes a need to better understand the tools we use to model their atmospheres. In this Paper, we present the protocol for the Comparing Atmospheric Models of Extrasolar Mini-Neptunes Building and Envisioning Retrievals and Transits, CAMEMBERT, project, an intercomparison of general circulation models (GCMs) used by the exoplanetary science community to simulate the atmospheres of mini-Neptunes. We focus on two targets well studied both observationally and theoretically with planned JWST cycle 1 observations: the warm GJ 1214b and the cooler K2-18b. For each target, we consider a temperature-forced case, a clear sky dual-gray radiative transfer case, and a clear sky multiband radiative transfer case, covering a range of complexities and configurations where we know differences exist between GCMs in the literature. This Paper presents all the details necessary to participate in the intercomparison, with the intention of presenting the results in future papers. Currently, there are eight GCMs participating (ExoCAM, Exo-FMS, FMS PCM, Generic PCM, MITgcm, RM-GCM, THOR, and the Unified Model), and membership in the project remains open. Those interested in participating are invited to contact the authors.
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Cazes-Boezio, Gabriel, Dimitris Menemenlis, and Carlos R. Mechoso. "Impact of ECCO Ocean-State Estimates on the Initialization of Seasonal Climate Forecasts." Journal of Climate 21, no. 9 (May 1, 2008): 1929–47. http://dx.doi.org/10.1175/2007jcli1574.1.
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Abstract The impact of ocean-state estimates generated by the consortium for Estimating the Circulation and Climate of the Ocean (ECCO) on the initialization of a coupled general circulation model (CGCM) for seasonal climate forecasts is examined. The CGCM consists of the University of California, Los Angeles, Atmospheric GCM (UCLA AGCM) and an ECCO ocean configuration of the Massachusetts Institute of Technology GCM (MITgcm). The forecasts correspond to ensemble seasonal hindcasts for the period 1993–2001. For the forecasts, the ocean component of the CGCM is initialized in either early March or in early June using ocean states provided either by an unconstrained forward ocean integration of the MITgcm (the “baseline” hindcasts) or by data-constrained ECCO results (the “ECCO” hindcasts). Forecast skill for both the baseline and the ECCO hindcasts is significantly higher than persistence and compares well with the skill of other state-of-the art CGCM forecast systems. For March initial conditions, the standard errors of sea surface temperature (SST) anomalies in ECCO hindcasts (relative to observed anomalies) are up to 1°C smaller than in the baseline hindcasts over the central and eastern equatorial Pacific (150°–120°W). For June initial conditions, the errors of ECCO hindcasts are up to 0.5°C smaller than in the baseline hindcasts. The smaller standard error of the ECCO hindcasts is, in part, due to a more realistic equatorial thermocline structure of the ECCO initial conditions. This study confirms the value of physically consistent ocean-state estimation for the initialization of seasonal climate forecasts.
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Lamona, Bernawis, Judith Hauck, and Christoph Völker. "Evaluation of a global ocean general circulation model; The Lat-Lon-Cap (LLC90) configuration of the MITgcm." IOP Conference Series: Earth and Environmental Science 162 (June 2018): 012002. http://dx.doi.org/10.1088/1755-1315/162/1/012002.
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Marshall, John, Jeffery Scott, and Andrey Proshutinsky. "“Climate response functions” for the Arctic Ocean: a proposed coordinated modelling experiment." Geoscientific Model Development 10, no. 7 (July 21, 2017): 2833–48. http://dx.doi.org/10.5194/gmd-10-2833-2017.
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Abstract. A coordinated set of Arctic modelling experiments, which explore how the Arctic responds to changes in external forcing, is proposed. Our goal is to compute and compare climate response functions (CRFs) – the transient response of key observable indicators such as sea-ice extent, freshwater content of the Beaufort Gyre, etc. – to abrupt step changes in forcing fields across a number of Arctic models. Changes in wind, freshwater sources, and inflows to the Arctic basin are considered. Convolutions of known or postulated time series of these forcing fields with their respective CRFs then yield the (linear) response of these observables. This allows the project to inform, and interface directly with, Arctic observations and observers and the climate change community. Here we outline the rationale behind such experiments and illustrate our approach in the context of a coarse-resolution model of the Arctic based on the MITgcm. We conclude by summarizing the expected benefits of such an activity and encourage other modelling groups to compute CRFs with their own models so that we might begin to document their robustness to model formulation, resolution, and parameterization.
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Sun, Rui, Aneesh C. Subramanian, Arthur J. Miller, Matthew R. Mazloff, Ibrahim Hoteit, and Bruce D. Cornuelle. "SKRIPS v1.0: a regional coupled ocean–atmosphere modeling framework (MITgcm–WRF) using ESMF/NUOPC, description and preliminary results for the Red Sea." Geoscientific Model Development 12, no. 10 (October 8, 2019): 4221–44. http://dx.doi.org/10.5194/gmd-12-4221-2019.
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Abstract. A new regional coupled ocean–atmosphere model is developed and its implementation is presented in this paper. The coupled model is based on two open-source community model components: the MITgcm ocean model and the Weather Research and Forecasting (WRF) atmosphere model. The coupling between these components is performed using ESMF (Earth System Modeling Framework) and implemented according to National United Operational Prediction Capability (NUOPC) protocols. The coupled model is named the Scripps–KAUST Regional Integrated Prediction System (SKRIPS). SKRIPS is demonstrated with a real-world example by simulating a 30 d period including a series of extreme heat events occurring on the eastern shore of the Red Sea region in June 2012. The results obtained by using the coupled model, along with those in forced stand-alone oceanic or atmospheric simulations, are compared with observational data and reanalysis products. We show that the coupled model is capable of performing coupled ocean–atmosphere simulations, although all configurations of coupled and uncoupled models have good skill in modeling the heat events. In addition, a scalability test is performed to investigate the parallelization of the coupled model. The results indicate that the coupled model code scales well and the ESMF/NUOPC coupler accounts for less than 5 % of the total computational resources in the Red Sea test case. The coupled model and documentation are available at https://library.ucsd.edu/dc/collection/bb1847661c (last access: 26 September 2019), and the source code is maintained at https://github.com/iurnus/scripps_kaust_model (last access: 26 September 2019).
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Anav, Alessandro, Adriana Carillo, Massimiliano Palma, Maria Vittoria Struglia, Ufuk Utku Turuncoglu, and Gianmaria Sannino. "The ENEA-REG system (v1.0), a multi-component regional Earth system model: sensitivity to different atmospheric components over the Med-CORDEX (Coordinated Regional Climate Downscaling Experiment) region." Geoscientific Model Development 14, no. 7 (July 2, 2021): 4159–85. http://dx.doi.org/10.5194/gmd-14-4159-2021.
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Abstract. In this study, a new regional Earth system model is developed and applied to the Med-CORDEX (Coordinated Regional Climate Downscaling Experiment) region. The ENEA-REG system is made up of two interchangeable regional climate models as atmospheric components (RegCM, REGional Climate Model, and WRF, Weather Research and Forecasting), a river model (Hydrological Discharge, HD), and an ocean model (Massachusetts Institute of Technology General Circulation Model, MITgcm); processes taking place at the land surface are represented within the atmospheric models with the possibility to use several land surface schemes of different complexity. The coupling between these components is performed through the RegESM driver. Here, we present and describe our regional Earth system model and evaluate its components using a multidecadal hindcast simulation over the period 1980–2013 driven by ERA-Interim reanalysis. We show that the atmospheric components correctly reproduce both large-scale and local features of the Euro-Mediterranean climate, although we found some remarkable biases: in particular, WRF has a significant cold bias during winter over the northeastern bound of the domain and a warm bias in the whole continental Europe during summer, while RegCM overestimates the wind speed over the Mediterranean Sea. Similarly, the ocean component correctly reproduces the analyzed ocean properties with performances comparable to the state-of-art coupled regional models contributing to the Med-CORDEX initiative. Our regional Earth system model allows studying the Euro-Mediterranean climate system and can be applied to both hindcast and scenario simulations.
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Bingham, Frederick M., Severine Fournier, Susannah Brodnitz, Karly Ulfsax, and Hong Zhang. "Matchup Characteristics of Sea Surface Salinity Using a High-Resolution Ocean Model." Remote Sensing 13, no. 15 (July 30, 2021): 2995. http://dx.doi.org/10.3390/rs13152995.
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Sea surface salinity (SSS) satellite measurements are validated using in situ observations usually made by surfacing Argo floats. Validation statistics are computed using matched values of SSS from satellites and floats. This study explores how the matchup process is done using a high-resolution numerical ocean model, the MITgcm. One year of model output is sampled as if the Aquarius and Soil Moisture Active Passive (SMAP) satellites flew over it and Argo floats popped up into it. Statistical measures of mismatch between satellite and float are computed, RMS difference (RMSD) and bias. The bias is small, less than 0.002 in absolute value, but negative with float values being greater than satellites. RMSD is computed using an “all salinity difference” method that averages level 2 satellite observations within a given time and space window for comparison with Argo floats. RMSD values range from 0.08 to 0.18 depending on the space–time window and the satellite. This range gives an estimate of the representation error inherent in comparing single point Argo floats to area-average satellite values. The study has implications for future SSS satellite missions and the need to specify how errors are computed to gauge the total accuracy of retrieved SSS values.
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Yang, Qinghua, Svetlana N. Losa, Martin Losch, Jiping Liu, Zhanhai Zhang, Lars Nerger, and Hu Yang. "Assimilating summer sea-ice concentration into a coupled ice–ocean model using a LSEIK filter." Annals of Glaciology 56, no. 69 (2015): 38–44. http://dx.doi.org/10.3189/2015aog69a740.
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AbstractThe decrease in summer sea-ice extent in the Arctic Ocean opens shipping routes and creates potential for many marine operations. For these activities accurate predictions of sea-ice conditions are required to maintain marine safety. In an attempt at Arctic sea-ice prediction, the summer of 2010 is selected to implement an Arctic sea-ice data assimilation (DA) study. The DA system is based on a regional Arctic configuration of the Massachusetts Institute of Technology general circulation model (MITgcm) and a local singular evolutive interpolated Kalman (LSEIK) filter to assimilate Special Sensor Microwave Imager/Sounder (SSMIS) sea-ice concentration operational products from the US National Snow and Ice Data Center (NSIDC). Based on comparisons with both the assimilated NSIDC SSMIS concentration and concentration data from the Ocean and Sea Ice Satellite Application Facility, the forecasted sea-ice edge and concentration improve upon simulations without data assimilation. By the nature of the assimilation algorithm with multivariate covariance between ice concentration and thickness, sea-ice thickness fields are also updated, and the evaluation with in situ observation shows some improvement compared to the forecast without data assimilation.
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Fu, Hongli, Xinrong Wu, Wei Li, Lianxin Zhang, Kexiu Liu, and Bo Dan. "Improving the accuracy of barotropic and internal tides embedded in a high-resolution global ocean circulation model of MITgcm." Ocean Modelling 162 (June 2021): 101809. http://dx.doi.org/10.1016/j.ocemod.2021.101809.
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Bingham, Frederick M., Susannah Brodnitz, Severine Fournier, Karly Ulfsax, Akiko Hayashi, and Hong Zhang. "Sea Surface Salinity Subfootprint Variability from a Global High-Resolution Model." Remote Sensing 13, no. 21 (November 2, 2021): 4410. http://dx.doi.org/10.3390/rs13214410.
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Subfootprint variability (SFV) is variability at a spatial scale smaller than the footprint of a satellite, and it cannot be resolved by satellite observations. It is important to quantify and understand, as it contributes to the error budget for satellite data. The purpose of this study was to estimate the SFV for sea surface salinity (SSS) satellite observations. This was performed by using a high-resolution numerical model, a 1/48° version of the MITgcm simulation, from which one year of output has recently become available. SFV, defined as the weighted standard deviation of SSS within the satellite footprint, was computed from the model for a 2° × 2° grid of points for the one model year. We present maps of median SFV for 40 and 100 km footprint size, display histograms of its distribution for a range of footprint sizes and quantify its seasonality. At a 100 km (40 km) footprint size, SFV has a mode of 0.06 (0.04). It is found to vary strongly by location and season. It has larger values in western-boundary and eastern-equatorial regions, as well as in a few other areas. SFV has strong variability throughout the year, with the largest values generally being in the fall season. We also quantified the representation error, the degree of mismatch between random samples within a footprint and the footprint average. Our estimates of SFV and representation error can be used in understanding errors in the satellite observation of SSS.
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Nakayama, Yoshihiro, Dimitris Menemenlis, Ou Wang, Hong Zhang, Ian Fenty, and An T. Nguyen. "Development of adjoint-based ocean state estimation for the Amundsen and Bellingshausen seas and ice shelf cavities using MITgcm–ECCO (66j)." Geoscientific Model Development 14, no. 8 (August 6, 2021): 4909–24. http://dx.doi.org/10.5194/gmd-14-4909-2021.
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Abstract. The Antarctic coastal ocean impacts sea level rise, deep-ocean circulation, marine ecosystems, and the global carbon cycle. To better describe and understand these processes and their variability, it is necessary to combine the sparse available observations with the best-possible numerical descriptions of ocean circulation. In particular, high ice shelf melting rates in the Amundsen Sea have attracted many observational campaigns, and we now have some limited oceanographic data that capture seasonal and interannual variability during the past decade. One method to combine observations with numerical models that can maximize the information extracted from the sparse observations is the adjoint method, a.k.a. 4D-Var (4-dimensional variational assimilation), as developed and implemented for global ocean state estimation by the Estimating the Circulation and Climate of the Ocean (ECCO) project. Here, for the first time, we apply the adjoint-model estimation method to a regional configuration of the Amundsen and Bellingshausen seas, Antarctica, including explicit representation of sub-ice-shelf cavities. We utilize observations available during 2010–2014, including ship-based and seal-tagged CTD measurements, moorings, and satellite sea-ice concentration estimates. After 20 iterations of the adjoint-method minimization algorithm, the cost function, here defined as a sum of the weighted model–data difference, is reduced by 65 % relative to the baseline simulation by adjusting initial conditions, atmospheric forcing, and vertical diffusivity. The sea-ice and ocean components of the cost function are reduced by 59 % and 70 %, respectively. Major improvements include better representations of (1) Winter Water (WW) characteristics and (2) intrusions of modified Circumpolar Deep Water (mCDW) towards the Pine Island Glacier. Sensitivity experiments show that ∼40 % and ∼10 % of improvements in sea ice and ocean state, respectively, can be attributed to the adjustment of air temperature and wind. This study is a preliminary demonstration of adjoint-method optimization with explicit representation of ice shelf cavity circulation. Despite the 65 % cost reduction, substantial model–data discrepancies remain, in particular with annual and interannual variability observed by moorings in front of the Pine Island Ice Shelf. We list a series of possible causes for these residuals, including limitations of the model, the optimization methodology, and observational sampling. In particular, we hypothesize that residuals could be further reduced if the model could more accurately represent sea-ice concentration and coastal polynyas.
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Ragon, Charline, Valerio Lembo, Valerio Lucarini, Christian Vérard, Jérôme Kasparian, and Maura Brunetti. "Robustness of Competing Climatic States." Journal of Climate 35, no. 9 (May 1, 2022): 2769–84. http://dx.doi.org/10.1175/jcli-d-21-0148.1.
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Abstract The climate is a nonequilibrium system undergoing the continuous action of forcing and dissipation. Under the effect of a spatially inhomogeneous absorption of solar energy, all the climate components dynamically respond until an approximate steady state (or attractor) is reached. However, multiple steady states can coexist for a given forcing and with the same boundary conditions. Here, we apply the Thermodynamic Diagnostic Tool (TheDiaTo) to investigate the statistical properties of five coexisting climates, ranging from a snowball to an ice-free aquaplanet, obtained in MITgcm coupled simulations. The aim is to explore the multistability of the climate model setup by highlighting differences in competing steady states and their characteristic signatures regarding the meridional transport of heat and water mass, the Lorenz energy cycle, and the material entropy production. We also investigate how such attractors change when the model configuration is varied. We consider, in particular, the effect of changing the representation of the cloud albedo, and of implementing an improved closure of the energy budget. We find that, even if the dynamics remain on the same attractor, state variables are modified. The set of metrics in TheDiaTo quantifies such modifications and represents a valuable tool for model evaluation.
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Querin, Stefano, Simone Cosoli, Riccardo Gerin, Célia Laurent, Vlado Malačič, Neva Pristov, and Pierre-Marie Poulain. "Multi-Platform, High-Resolution Study of a Complex Coastal System: The TOSCA Experiment in the Gulf of Trieste." Journal of Marine Science and Engineering 9, no. 5 (April 27, 2021): 469. http://dx.doi.org/10.3390/jmse9050469.
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Although small in size, the Gulf of Trieste (GoT), a marginal coastal basin in the northern Adriatic Sea, is characterized by very complex dynamics and strong variability of its oceanographic conditions. In April–May 2012, a persistent, large-scale anticyclonic eddy was observed in the GoT. This event was captured by both High Frequency Radar (HFR) and Lagrangian drifter observations collected within the European MED TOSCA (Tracking Oil Spill and Coastal Awareness) project. The complexity of the system and the variety of forcing factors constitute major challenges from a numerical modeling perspective when it comes to simulating the observed features. In this study, we implemented a high-resolution hydrodynamic model in an attempt to reproduce and analyze the observed basin-wide eddy structure and determine its drivers. We adopted the Massachusetts Institute of Technology General Circulation Model (MITgcm), tailored for the GoT, nested into a large-scale simulation of the Adriatic Sea and driven by a tidal model, measured river freshwater discharge data and surface atmospheric forcing. Numerical results were qualitatively and quantitatively evaluated against HFR surface current maps, Lagrangian drifter trajectories and thermohaline data, showing good skills in reproducing the general circulation, but failing in accurately tracking the drifters. Model sensitivity to different forcing factors (wind, river and tides) was also assessed.
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Li, Zhiyuan, Daji Huang, Chuanxi Xing, and Xiuyang Lü. "The synoptic variation of Yellow Sea Warm Current in winter and its mechanisms." International Journal of Numerical Methods for Heat & Fluid Flow 29, no. 2 (February 4, 2019): 724–37. http://dx.doi.org/10.1108/hff-05-2018-0255.
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Purpose This paper aims to investigate the basin-scale features and mechanisms of the synoptic variation of Yellow Sea Warm Current (YSWC) in winter. Design/methodology/approach Both in situ current observation and numerical model (MITgcm) were conducted to investigate the synoptic variation of YSWC. The model was well validated and the simulated results were analyzed. Findings The YSWC shows a much stronger synoptic variation than its mean in winter with strong variation mainly in the deep central YS. The synoptic variation of YSWC is associated a counterclockwise rotary wave as a response to the strong northerly wind bursts. Strong northerly wind generates a large sea surface height (SSH) drop in the Bohai Sea and northern YS. Then, the SSH rotates in a counterclockwise manner. About 18 h later, strong eastward SSH gradient is formed, generating a northward current through geostrophic balance. Originality/value The mechanisms analysis shows that the synoptic variation of YSWC is intrinsically linked to SSH as a response to the synoptic varying winter monsoon. This study provides an insight into the spatial and temporal evolution of the oceanic response to strong northerly wind in winter.
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Le Fouest, V., M. Manizza, B. Tremblay, and M. Babin. "Modelling the impact of riverine DON removal by marine bacterioplankton on primary production in the Arctic Ocean." Biogeosciences 12, no. 11 (June 4, 2015): 3385–402. http://dx.doi.org/10.5194/bg-12-3385-2015.
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Abstract. The planktonic and biogeochemical dynamics of the Arctic shelves exhibit a strong variability in response to Arctic warming. In this study, we employ a biogeochemical model coupled to a pan-Arctic ocean–sea ice model (MITgcm) to elucidate the processes regulating the primary production (PP) of phytoplankton, bacterioplankton (BP), and their interactions. The model explicitly simulates and quantifies the contribution of usable dissolved organic nitrogen (DON) drained by the major circum-Arctic rivers to PP and BP in a scenario of melting sea ice (1998–2011). Model simulations suggest that, on average between 1998 and 2011, the removal of usable riverine dissolved organic nitrogen (RDON) by bacterioplankton is responsible for a ~ 26% increase in the annual BP for the whole Arctic Ocean. With respect to total PP, the model simulates an increase of ~ 8% on an annual basis and of ~ 18% in summer. Recycled ammonium is responsible for the PP increase. The recycling of RDON by bacterioplankton promotes higher BP and PP, but there is no significant temporal trend in the BP : PP ratio within the ice-free shelves over the 1998–2011 period. This suggests no significant evolution in the balance between autotrophy and heterotrophy in the last decade, with a constant annual flux of RDON into the coastal ocean, although changes in RDON supply and further reduction in sea-ice cover could potentially alter this delicate balance.
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Yang, Qinghua, Martin Losch, Svetlana N. Losa, Thomas Jung, and Lars Nerger. "Taking into Account Atmospheric Uncertainty Improves Sequential Assimilation of SMOS Sea Ice Thickness Data in an Ice–Ocean Model." Journal of Atmospheric and Oceanic Technology 33, no. 3 (March 2016): 397–407. http://dx.doi.org/10.1175/jtech-d-15-0176.1.
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AbstractThe sensitivity of assimilating sea ice thickness data to uncertainty in atmospheric forcing fields is examined using ensemble-based data assimilation experiments with the Massachusetts Institute of Technology General Circulation Model (MITgcm) in the Arctic Ocean during November 2011–January 2012 and the Met Office (UKMO) ensemble atmospheric forecasts. The assimilation system is based on a local singular evolutive interpolated Kalman (LSEIK) filter. It combines sea ice thickness data derived from the European Space Agency’s (ESA) Soil Moisture Ocean Salinity (SMOS) satellite and Special Sensor Microwave Imager/Sounder (SSMIS) sea ice concentration data with the numerical model. The effect of representing atmospheric uncertainty implicit in the ensemble forcing is assessed by three different assimilation experiments. The first two experiments use a single deterministic forcing dataset and a different forgetting factor to inflate the ensemble spread. The third experiment uses 23 members of the UKMO atmospheric ensemble prediction system. It avoids additional ensemble inflation and is hence easier to implement. As expected, the model-data misfits are substantially reduced in all three experiments, but with the ensemble forcing the errors in the forecasts of sea ice concentration and thickness are smaller compared to the experiments with deterministic forcing. This is most likely because the ensemble forcing results in a more plausible spread of the model state ensemble, which represents model uncertainty and produces a better forecast.
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Dong, Jihai, Baylor Fox-Kemper, Hong Zhang, and Changming Dong. "The Scale and Activity of Symmetric Instability Estimated from a Global Submesoscale-Permitting Ocean Model." Journal of Physical Oceanography 51, no. 5 (May 2021): 1655–70. http://dx.doi.org/10.1175/jpo-d-20-0159.1.
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AbstractSymmetric instability (SI) extracts kinetic energy from fronts in the surface mixed layer (SML), potentially affecting the SML structure and dynamics. Here, a global submesoscale-permitting ocean model named MITgcm LLC4320 simulation is used to examine the Stone linear prediction of the maximum SI scale to estimate grid spacings needed to begin resolving SI. Furthermore, potential effects of SI on the usable wind work are estimated roughly: this estimate of SI “activity” is useful for assessing if these modes should be resolved or parameterized. The maximum SI scale varies by latitude with median values from 568 to 23 m. Strong seasonality is observed in the SI scale and activity. The median scale in winter is 188 m globally, 2.5 times of that of summer (75 m). SI is more active in winter: 15% of the time compared with 6% in summer. The strongest SI activity is found in the western Pacific, western Atlantic, and Southern Oceans. The required grid spacings for a global model to begin resolving SI eddies in the SML are 24 m (50% of regions resolved) and 7.9 m (90%) in winter, decreasing to 9.4 m (50%) and 3.6 m (90%) in summer. It is also estimated that SI may reduce usable wind work by an upper bound of 0.83 mW m−2 globally, or 5% of the global magnitude. The sensitivity of these estimates to empirical thresholds is provided in the text.
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Heimbach, Patrick, and Martin Losch. "Adjoint sensitivities of sub-ice-shelf melt rates to ocean circulation under the Pine Island Ice Shelf, West Antarctica." Annals of Glaciology 53, no. 60 (2012): 59–69. http://dx.doi.org/10.3189/2012/aog60a025.
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AbstractWe investigate the sensitivity of sub-ice-shelf melt rates under Pine Island Ice Shelf, West Antarctica, to changes in the oceanic state using an adjoint ocean model that is capable of representing the flow in sub-ice-shelf cavities. The adjoint code is based on algorithmic differentiation (AD) of the Massachusetts Institute of Technology’s ocean general circulation model (MITgcm). The adjoint model was extended by adding into the AD process the corresponding sub-ice-shelf cavity code, which implements a three-equation thermodynamic melt-rate parameterization to infer heat and freshwater fluxes at the ice-shelf/ocean boundary. The inferred sensitivities reveal dominant timescales of 30–60 days over which the shelf exit is connected to the deep interior via advective processes. They exhibit rich three-dimensional time-evolving patterns that can be understood in terms of a combination of the buoyancy forcing by inflowing water masses, the cavity geometry and the effect of rotation and topography in steering the flow in the presence of prominent features in the bedrock bathymetry. Dominant sensitivity pathways are found over a sill, as well as ‘shadow regions’ of very low sensitivities. To the extent that these transient patterns are robust they carry important information for decision-making in observation deployment and monitoring.
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Xu, Yun, Eric Rignot, Dimitris Menemenlis, and Michele Koppes. "Numerical experiments on subaqueous melting of Greenland tidewater glaciers in response to ocean warming and enhanced subglacial discharge." Annals of Glaciology 53, no. 60 (2012): 229–34. http://dx.doi.org/10.3189/2012aog60a139.
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AbstractThe largest dischargers of ice in Greenland are glaciers that terminate in the ocean and melt in contact with sea water. Studies of ice-sheet/ocean interactions have mostly focused on melting beneath near-horizontal floating ice shelves. For tidewater glaciers, melting instead takes place along the vertical face of the calving front. Here we modify the Massachusetts Institute of Technology general circulation model (MITgcm) to include ice melting from a calving face with the freshwater outflow at the glacier grounding line. We use the model to predict melt rates and their sensitivity to ocean thermal forcing and to subglacial discharge. We find that melt rates increase with approximately the one-third power of the subglacial water flux, and increase linearly with ocean thermal forcing. Our simulations indicate that, consistent with limited field data, melting ceases when subglacial discharge is shut off, and reaches several meters per day when subglacial discharge is high in the summer. These results are a first step toward a more realistic representation of subglacial discharge and of ocean thermal forcing on the subaqueous melting of tidewater glaciers in a numerical ocean model. Our results illustrate that the ice-front melting process is both complex and strongly time-dependent.
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McKiver, W. J., G. Sannino, F. Braga, and D. Bellafiore. "Investigation of model capability in capturing vertical hydrodynamic coastal processes: a case study in the north Adriatic Sea." Ocean Science 12, no. 1 (January 15, 2016): 51–69. http://dx.doi.org/10.5194/os-12-51-2016.
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Abstract. In this work we consider a numerical study of hydrodynamics in the coastal zone using two different models, SHYFEM (shallow water hydrodynamic finite element model) and MITgcm (Massachusetts Institute of Technology general circulation model), to assess their capability to capture the main processes. We focus on the north Adriatic Sea during a strong dense water event that occurred at the beginning of 2012. This serves as an interesting test case to examine both the models strengths and weaknesses, while giving an opportunity to understand how these events affect coastal processes, like upwelling and downwelling, and how they interact with estuarine dynamics. Using the models we examine the impact of setup, surface and lateral boundary treatment, resolution and mixing schemes, as well as assessing the importance of nonhydrostatic dynamics in coastal processes. Both models are able to capture the dense water event, though each displays biases in different regions. The models show large differences in the reproduction of surface patterns, identifying the choice of suitable bulk formulas as a central point for the correct simulation of the thermohaline structure of the coastal zone. Moreover, the different approaches in treating lateral freshwater sources affect the vertical coastal stratification. The results indicate the importance of having high horizontal resolution in the coastal zone, specifically in close proximity to river inputs, in order to reproduce the effect of the complex coastal morphology on the hydrodynamics. A lower resolution offshore is acceptable for the reproduction of the dense water event, even if specific vortical structures are missed. Finally, it is found that nonhydrostatic processes are of little importance for the reproduction of dense water formation in the shelf of the north Adriatic Sea.
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Hariri, Saeed. "Near-Surface Transport Properties and Lagrangian Statistics during Two Contrasting Years in the Adriatic Sea." Journal of Marine Science and Engineering 8, no. 9 (September 4, 2020): 681. http://dx.doi.org/10.3390/jmse8090681.
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This paper describes the near-surface transport properties and Lagrangian statistics in the Adriatic semi-enclosed basin using synthetic drifters. Lagrangian transport models were used to simulate synthetic trajectories from the mean flow fields obtained by the Massachusetts Institute of Technology general circulation model (MITgcm), implemented in the Adriatic from October 2006 until December 2008. In particular, the surface circulation properties in two contrasting years (2007 had a mild winter and cold fall, while 2008 had a normal winter and hot summer) are compared here. In addition, the Lagrangian statistics for the entire Adriatic Basin after removing the Eulerian mean circulation for numerical particles were calculated. The results indicate that the numerical particles were slower in this simulation when compared with the real drifters. This is because of the reduced energetic flow field generated by the MIT general circulation model during the selected years. The numerical results showed that the balanced effects of the wind-driven recirculation in the northernmost area(which would be a sea response to the Bora wind field) and the Po River discharge cause the residence times to be similar during the two selected years (182 and 185 days in 2007 and 2008, respectively). Furthermore, the mean angular momentum, diffusivity, and Lagrangian velocity covariance values are smaller than in the real drifter observations, while the maximum Lagrangian integral time scale is the same.
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Rudnick, Daniel L., Ganesh Gopalakrishnan, and Bruce D. Cornuelle. "Cyclonic Eddies in the Gulf of Mexico: Observations by Underwater Gliders and Simulations by Numerical Model." Journal of Physical Oceanography 45, no. 1 (January 2015): 313–26. http://dx.doi.org/10.1175/jpo-d-14-0138.1.
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AbstractCirculation in the Gulf of Mexico (GoM) is dominated by the Loop Current (LC) and by Loop Current eddies (LCEs) that form at irregular multimonth intervals by separation from the LC. Comparatively small cyclonic eddies (CEs) are thought to have a controlling influence on the LCE, including its separation from the LC. Because the CEs are so dynamic and short-lived, lasting only a few weeks, they have proved a challenge to observe. This study addresses that challenge using underwater gliders. These gliders’ data and satellite sea surface height (SSH) are used in a four-dimensional variational (4DVAR) assimilation in the Massachusetts Institute of Technology (MIT) general circulation model (MITgcm). The model serves two purposes: first, the model’s estimate of ocean state allows the analysis of four-dimensional fields, and second, the model forecasts are examined to determine the value of glider data. CEs have a Rossby number of about 0.2, implying that the effects of flow curvature, cyclostrophy, to modify the geostrophic momentum balance are slight. The velocity field in CEs is nearly depth independent, while LCEs are more baroclinic, consistent with the CEs origin on the less stratified, dense side of the LCE. CEs are formed from water in the GoM, rather than the Atlantic water that distinguishes the LCE. Model forecasts are improved by glider data, using a quality metric based on satellite SSH, with the best 2-month GoM forecast rivaling the accuracy of a global hindcast.
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Le Fouest, V., M. Manizza, B. Tremblay, and M. Babin. "Modeling the impact of riverine DON removal by marine bacterioplankton on primary production in the Arctic Ocean." Biogeosciences Discussions 11, no. 12 (December 9, 2014): 16953–92. http://dx.doi.org/10.5194/bgd-11-16953-2014.
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Abstract. The planktonic and biogeochemical dynamics of the Arctic shelves exhibit a strong variability in response to Arctic warming. In this study, in order to elucidate on the processes regulating the production of phytoplankton (PP) and bacterioplankton (BP) and their interactions, we employ a biogeochemical model coupled to a pan-Arctic ocean-sea ice model (MITgcm) to explicitly simulate and quantify the contribution of usable dissolved organic nitrogen (DON) drained by the major circum-Arctic rivers on PP and BP in a scenario of melting sea ice (1998–2011). Model simulations suggest that on average between 1998 and 2011, the removal of usable RDON by bacterioplankton is responsible of a ~26% increase of the annual BP for the whole Arctic Ocean. With respect to total PP, the model simulates an increase of ~8% on an annual basis and of ~18% in summer. Recycled ammonium is responsible for the PP increase. The recycling of RDON by bacterioplankton promotes higher BP and PP but there is no significant temporal trend in the BP : PP ratio within the ice-free shelves over the 1998–2011 period. This suggests no significant evolution in the balance between autotrophy and heterotrophy in the last decade with a constant annual flux of RDON into the coastal ocean although changes in RDON supply and further reduction in sea ice cover could potentially alter this delicate balance.
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Forget, G., J. M. Campin, P. Heimbach, C. N. Hill, R. M. Ponte, and C. Wunsch. "ECCO version 4: an integrated framework for non-linear inverse modeling and global ocean state estimation." Geoscientific Model Development Discussions 8, no. 5 (May 5, 2015): 3653–743. http://dx.doi.org/10.5194/gmdd-8-3653-2015.
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Abstract. This paper presents the ECCO v4 non-linear inverse modeling framework and its baseline solution for the evolving ocean state over the period 1992–2011. Both components are publicly available and highly integrated with the MITgcm. They are both subjected to regular, automated regression tests. The modeling framework includes sets of global conformal grids, a global model setup, implementations of model-data constraints and adjustable control parameters, an interface to algorithmic differentiation, as well as a grid-independent, fully capable Matlab toolbox. The reference ECCO v4 solution is a dynamically consistent ocean state estimate (ECCO-Production, release 1) without un-identified sources of heat and buoyancy, which any interested user will be able to reproduce accurately. The solution is an acceptable fit to most data and has been found physically plausible in many respects, as documented here and in related publications. Users are being provided with capabilities to assess model-data misfits for themselves. The synergy between modeling and data synthesis is asserted through the joint presentation of the modeling framework and the state estimate. In particular, the inverse estimate of parameterized physics was instrumental in improving the fit to the observed hydrography, and becomes an integral part of the ocean model setup available for general use. More generally, a first assessment of the relative importance of external, parametric and structural model errors is presented. Parametric and external model uncertainties appear to be of comparable importance and dominate over structural model uncertainty. The results generally underline the importance of including turbulent transport parameters in the inverse problem.
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DE ANDRÉS, E., J. OTERO, F. NAVARRO, A. PROMIŃSKA, J. LAPAZARAN, and W. WALCZOWSKI. "A two-dimensional glacier–fjord coupled model applied to estimate submarine melt rates and front position changes of Hansbreen, Svalbard." Journal of Glaciology 64, no. 247 (September 26, 2018): 745–58. http://dx.doi.org/10.1017/jog.2018.61.
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ABSTRACTWe have developed a two-dimensional coupled glacier–fjord model, which runs automatically using Elmer/Ice and MITgcm software packages, to investigate the magnitude of submarine melting along a vertical glacier front and its potential influence on glacier calving and front position changes. We apply this model to simulate the Hansbreen glacier–Hansbukta proglacial–fjord system, Southwestern Svalbard, during the summer of 2010. The limited size of this system allows us to resolve some of the small-scale processes occurring at the ice–ocean interface in the fjord model, using a 0.5 s time step and a 1 m grid resolution near the glacier front. We use a rich set of field data spanning the period April–August 2010 to constrain, calibrate and validate the model. We adjust circulation patterns in the fjord by tuning subglacial discharge inputs that best match observed temperature while maintaining a compromise with observed salinity, suggesting a convectively driven circulation in Hansbukta. The results of our model simulations suggest that both submarine melting and crevasse hydrofracturing exert important controls on seasonal frontal ablation, with submarine melting alone not being sufficient for reproducing the observed patterns of seasonal retreat. Both submarine melt and calving rates accumulated along the entire simulation period are of the same order of magnitude, ~100 m. The model results also indicate that changes in submarine melting lag meltwater production by 4–5 weeks, which suggests that it may take up to a month for meltwater to traverse the englacial and subglacial drainage network.
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Komacek, Thaddeus D., Xianyu Tan, Peter Gao, and Elspeth K. H. Lee. "Patchy Nightside Clouds on Ultra-hot Jupiters: General Circulation Model Simulations with Radiatively Active Cloud Tracers." Astrophysical Journal 934, no. 1 (July 1, 2022): 79. http://dx.doi.org/10.3847/1538-4357/ac7723.
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Abstract The atmospheres of ultra-hot Jupiters have been characterized in detail through recent phase curve and low- and high-resolution emission and transmission spectroscopic observations. Previous numerical studies have analyzed the effect of the localized recombination of hydrogen on the atmospheric dynamics and heat transport of ultra-hot Jupiters, finding that hydrogen dissociation and recombination lead to a reduction in the day-to-night contrasts of ultra-hot Jupiters relative to previous expectations. In this work, we add to previous efforts by also considering the localized condensation of clouds in the atmospheres of ultra-hot Jupiters, their resulting transport by the atmospheric circulation, and the radiative feedback of clouds on the atmospheric dynamics. To do so, we include radiatively active cloud tracers into the existing MITgcm framework for simulating the atmospheric dynamics of ultra-hot Jupiters. We take cloud condensate properties appropriate for the high-temperature condensate corundum from CARMA cloud microphysics models. We conduct a suite of general circulation model (GCM) simulations with varying cloud microphysical and radiative properties, and we find that partial cloud coverage is a ubiquitous outcome of our simulations. This patchy cloud distribution is inherently set by atmospheric dynamics in addition to equilibrium cloud condensation, and causes a cloud greenhouse effect that warms the atmosphere below the cloud deck. Nightside clouds are further sequestered at depth due to a dynamically induced high-altitude thermal inversion. We post-process our GCMs with the Monte Carlo radiative transfer code gCMCRT and find that the patchy clouds on ultra-hot Jupiters do not significantly impact transmission spectra but can affect their phase-dependent emission spectra.
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Villas Bôas, Ana B., Bruce D. Cornuelle, Matthew R. Mazloff, Sarah T. Gille, and Fabrice Ardhuin. "Wave–Current Interactions at Meso- and Submesoscales: Insights from Idealized Numerical Simulations." Journal of Physical Oceanography 50, no. 12 (December 2020): 3483–500. http://dx.doi.org/10.1175/jpo-d-20-0151.1.
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AbstractSurface gravity waves play a major role in the exchange of momentum, heat, energy, and gases between the ocean and the atmosphere. The interaction between currents and waves can lead to variations in the wave direction, frequency, and amplitude. In the present work, we use an ensemble of synthetic currents to force the wave model WAVEWATCH III and assess the relative impact of current divergence and vorticity in modifying several properties of the waves, including direction, period, directional spreading, and significant wave height Hs. We find that the spatial variability of Hs is highly sensitive to the nature of the underlying current and that refraction is the main mechanism leading to gradients of Hs. The results obtained using synthetic currents were used to interpret the response of surface waves to realistic currents by running an additional set of simulations using the llc4320 MITgcm output in the California Current region. Our findings suggest that wave parameters could be used to detect and characterize strong gradients in the velocity field, which is particularly relevant for the Surface Water and Ocean Topography (SWOT) satellite as well as several proposed satellite missions.
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McKiver, W. J., G. Sannino, F. Braga, and D. Bellafiore. "Investigation of model capability in capturing vertical hydrodynamic coastal processes: a case study in the North Adriatic Sea." Ocean Science Discussions 12, no. 4 (August 3, 2015): 1625–68. http://dx.doi.org/10.5194/osd-12-1625-2015.
Full textAbstract:
Abstract. In this work we consider a numerical study of hydrodynamics in the coastal zone using two different models, SHYFEM and MITgcm, to assess their capability to capture the main processes. We focus on the North Adriatic Sea during a strong dense water event that occurred at the beginning of 2012. This serves as an interesting test case to examine both the models strengths and weaknesses, while giving an opportunity to understand how these events affect coastal processes, like upwelling and downwelling, and how they interact with estuarine dynamics. Using the models we examine the impact of setup, surface and lateral boundary treatment, resolution and mixing schemes, as well as assessing the importance of nonhydrostatic dynamics in coastal processes. Both models are able to capture the dense water event, though each displays biases in different regions. The models show large differences in the reproduction of surface patterns, identifying the choice of suitable bulk formulas as a central point for the correct simulation of the thermohaline structure of the coastal zone. Moreover, the different approaches in treating lateral freshwater sources affect the vertical coastal stratification. The results indicate the importance of having high horizontal resolution in the coastal zone, specifically in close proximity to river inputs, in order to reproduce the effect of the complex coastal morphology on the hydrodynamics. A lower resolution offshore is acceptable for the reproduction of the dense water event, even if specific vortical structures are missed. Finally, it is found that nonhydrostatic processes are of little importance for the reproduction of dense water formation in the shelf of the North Adriatic Sea.
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Ashkenazy, Yosef, and Eli Tziperman. "A Wind-Induced Thermohaline Circulation Hysteresis and Millennial Variability Regimes." Journal of Physical Oceanography 37, no. 10 (October 1, 2007): 2446–57. http://dx.doi.org/10.1175/jpo3124.1.
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Abstract The multiple equilibria of the thermohaline circulation (THC: used here in the sense of the meridional overturning circulation) as function of the surface freshwater flux has been studied intensively following a Stommel paper from 1961. It is shown here that multistability and hysteresis of the THC also exist when the wind stress amplitude is varied as a control parameter. Both the Massachusetts Institute of Technology ocean general circulation model (MITgcm) and a simple three-box model are used to study and explain different dynamical regimes of the THC and THC variability as a function of the wind stress amplitude. Starting with active winds and a thermally dominant thermohaline circulation state, the wind stress amplitude is slowly reduced to zero over a time period of ∼40 000 yr (40 kyr) and then increased again to its initial value over another ∼40 kyr. It is found that during the decreasing wind stress phase, the THC remains thermally dominant until very low wind stress amplitude at which pronounced Dansgaard–Oeschger-like THC relaxation oscillations are initiated. However, while the wind stress amplitude is increased, these relaxation oscillations are present up to significantly larger wind stress amplitude. The results of this study thus suggest that under the same wind stress amplitude, the THC can be either in a stable thermally dominant state or in a pronounced relaxation oscillations state. The simple box model analysis suggests that the observed hysteresis is due to the combination of the Stommel hysteresis and the Winton and Sarachik “deep decoupling” oscillations.
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Yang, Q., M. Losch, S. Losa, T. Jung, L. Nerger, and T. Lavergne. "The benefit of using sea ice concentration satellite data products with uncertainty estimates in summer sea ice data assimilation." Cryosphere Discussions 9, no. 2 (April 21, 2015): 2543–62. http://dx.doi.org/10.5194/tcd-9-2543-2015.
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Abstract. We present sensitivity experiments in which the Ocean and Sea Ice Satellite Application Facility (OSISAF) near-real time sea ice concentration data and the recently released Sea Ice Climate Change Initiative (SICCI) data are assimilated during summer. The data assimilation system uses the MIT general circulation model (MITgcm) and a local Singular Evolutive Interpolated Kalman (LSEIK) filter. Atmospheric forcing uncertainties are modelled by using atmospheric ensemble forcing which is taken from the UK Met Office (UKMO) system available through the TIGGE (THORPEX Interactive Grand Global Ensemble) database. When a constant data uncertainty is assumed, the assimilation of SICCI concentrations outperforms the assimilation of OSISAF data in both concentration and thickness forecasts. This is probably because the SICCI data retrieval uses an improved processing algorithms and methodologies. For the assimilation of SICCI data, using the observation uncertainties that are provided with the data improves the ensemble mean state of ice concentration compared to using constant data errors, but does not improve the ice thickness. This is caused by a mismatch between the SICCI concentration and the modelled physical ice concentration. To account for this mismatch the SICCI product should feature larger uncertainties in summer. Consistently, thickness forecasts can be improved by raising the minimum observation uncertainty to inflate the underestimated data error and ensemble spread.
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Yang, Shengmu, Jiuxing Xing, Daoyi Chen, and Shengli Chen. "A modelling study of eddy-splitting by an island/seamount." Ocean Science 13, no. 5 (October 25, 2017): 837–49. http://dx.doi.org/10.5194/os-13-837-2017.
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Abstract. A mesoscale eddy's trajectory and its interaction with topography under the planetary β and nonlinear effects in the South China Sea are examined using the MIT General Circulation Model (MITgcm). Warm eddies propagate to the southwest while cold eddies propagate to the northwest. The propagation speed of both warm and cold eddies is about 2.4 km day−1 in the model. The eddy trajectory and its structure are affected by an island or a seamount, in particular, under certain conditions, the eddy may split during the interaction with an island/seamount. We focus this research on two parameters R and S (where R and S are two dimensionless parameters of the island size and submergence depth; R is the ratio of the island radius to the eddy radius, and S is the ratio of the seamount submergence depth to the eddy vertical length). The results of sensitivity experiments with varying island or seamount geometry indicate that the eddy would split in the qualitative range of 1∕4 < R < 2 and S < 1∕5. The scale of the secondary eddy split-off decreases as the island diameter or the seamount submergence depth increases. In the splitting process, besides the off-spring eddy, there are also some filaments or eddies with opposite vorticity appearing around the eddy. Eddy-splitting, therefore, is an important way to transform energy from the mesoscale to sub-mesoscale in the ocean.
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Vazquez, Heriberto J., Ganesh Gopalakrishnan, and Julio Sheinbaum. "Impact of Yucatan Channel Subsurface Velocity Observations on the Gulf of Mexico State Estimates." Journal of Physical Oceanography 53, no. 1 (January 2023): 361–85. http://dx.doi.org/10.1175/jpo-d-21-0213.1.
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Abstract The Gulf of Mexico (GoM) surface circulation variability is dominated by the Loop Current (LC) and the episodically released anticyclonic Loop Current eddies (LCEs). The Yucatan Current feeds the LC through the Yucatan Channel (YC), and its flow structure at the YC is hypothesized to affect the LC evolution critically. This study examines the impact of assimilating YC subsurface velocity observations from a tall mooring array across the YC on the GoM circulation. State estimates and forecasts of the LC circulation were produced using a regional implementation of the Massachusetts Institute of Technology general circulation model (MITgcm) and its adjoint-based four-dimensional variational (4DVAR) assimilation system. The estimates were constrained by combinations of the YC observations and satellite-derived sea surface height (SSH) and sea surface temperature (SST). The results show that assimilation of both moored and satellite data improves the model hindcasts and forecasts for all LC phases. Additionally, one realization of the state estimate that assimilates only moored data matches the LCE detachment timing with that of AVISO SSH. Observations from the moorings close to the Yucatan Peninsula significantly impact the LCE detachment. A finite-time Lyapunov exponent analysis reveals the differences among the assimilation experiments, such as eddylike structures intruding into the GoM through the YC, and its relation to the typical LC sudden growth. Finally, an adjoint sensitivity analysis is used to verify the dynamic link between the LC extension and the intrusion of eddylike structures into the GoM.
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Zanna, Laure, Patrick Heimbach, Andrew M. Moore, and Eli Tziperman. "The Role of Ocean Dynamics in the Optimal Growth of Tropical SST Anomalies." Journal of Physical Oceanography 40, no. 5 (May 1, 2010): 983–1003. http://dx.doi.org/10.1175/2009jpo4196.1.
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Abstract The role of ocean dynamics in optimally exciting interannual variability of tropical sea surface temperature (SST) anomalies is investigated using an idealized-geometry ocean general circulation model. Initial temperature and salinity perturbations leading to an optimal growth of tropical SST anomalies, typically arising from the nonnormal dynamics, are evaluated. The structure of the optimal perturbations is characterized by relatively strong deep salinity anomalies near the western boundary generating a transient amplification of equatorial SST anomalies in less than four years. The associated growth mechanism is linked to the excitation of coastal and equatorial Kelvin waves near the western boundary following a rapid geostrophic adjustment owing to the optimal initial temperature and salinity perturbations. The results suggest that the nonnormality of the ocean dynamics may efficiently create large tropical SST variability on interannual time scales in the Atlantic without the participation of air–sea processes or the meridional overturning circulation. An optimal deep initial salinity perturbation of 0.1 ppt located near the western boundary can result in a tropical SST anomaly of approximately 0.45°C after nearly four years, assuming the dynamics are linear. Possible mechanisms for exciting such deep perturbations are discussed. While this study is motivated by tropical Atlantic SST variability, its relevance to other basins is not excluded. The optimal initial conditions leading to the tropical SST anomalies’ growth are obtained by solving a generalized eigenvalue problem. The evaluation of the optimals is achieved by using the Massachusetts Institute of Technology general circulation model (MITgcm) tangent linear and adjoint models as well the the Arnoldi Package (ARPACK) software for solving large-scale eigenvalue problems.
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Bigdeli, Arash, Brice Loose, An T. Nguyen, and Sylvia T. Cole. "Numerical investigation of the Arctic ice–ocean boundary layer and implications for air–sea gas fluxes." Ocean Science 13, no. 1 (January 23, 2017): 61–75. http://dx.doi.org/10.5194/os-13-61-2017.
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Abstract. In ice-covered regions it is challenging to determine constituent budgets – for heat and momentum, but also for biologically and climatically active gases like carbon dioxide and methane. The harsh environment and relative data scarcity make it difficult to characterize even the physical properties of the ocean surface. Here, we sought to evaluate if numerical model output helps us to better estimate the physical forcing that drives the air–sea gas exchange rate (k) in sea ice zones. We used the budget of radioactive 222Rn in the mixed layer to illustrate the effect that sea ice forcing has on gas budgets and air–sea gas exchange. Appropriate constraint of the 222Rn budget requires estimates of sea ice velocity, concentration, mixed-layer depth, and water velocities, as well as their evolution in time and space along the Lagrangian drift track of a mixed-layer water parcel. We used 36, 9 and 2 km horizontal resolution of regional Massachusetts Institute of Technology general circulation model (MITgcm) configuration with fine vertical spacing to evaluate the capability of the model to reproduce these parameters. We then compared the model results to existing field data including satellite, moorings and ice-tethered profilers. We found that mode sea ice coverage agrees with satellite-derived observation 88 to 98 % of the time when averaged over the Beaufort Gyre, and model sea ice speeds have 82 % correlation with observations. The model demonstrated the capacity to capture the broad trends in the mixed layer, although with a significant bias. Model water velocities showed only 29 % correlation with point-wise in situ data. This correlation remained low in all three model resolution simulations and we argued that is largely due to the quality of the input atmospheric forcing. Overall, we found that even the coarse-resolution model can make a modest contribution to gas exchange parameterization, by resolving the time variation of parameters that drive the 222Rn budget, including rate of mixed-layer change and sea ice forcings.
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Wardenier, Joost P., Vivien Parmentier, Elspeth K. H. Lee, Michael R. Line, and Ehsan Gharib-Nezhad. "Decomposing the iron cross-correlation signal of the ultra-hot Jupiter WASP-76b in transmission using 3D Monte Carlo radiative transfer." Monthly Notices of the Royal Astronomical Society 506, no. 1 (June 26, 2021): 1258–83. http://dx.doi.org/10.1093/mnras/stab1797.
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ABSTRACT Ultra-hot Jupiters are tidally locked gas giants with dayside temperatures high enough to dissociate hydrogen and other molecules. Their atmospheres are vastly non-uniform in terms of chemistry, temperature, and dynamics, and this makes their high-resolution transmission spectra and cross-correlation signal difficult to interpret. In this work, we use the SPARC/MITgcm global circulation model to simulate the atmosphere of the ultra-hot Jupiter WASP-76b under different conditions, such as atmospheric drag and the absence of TiO and VO. We then employ a 3D Monte Carlo radiative transfer code, hires-mcrt, to self-consistently model high-resolution transmission spectra with iron (Fe i) lines at different phases during the transit. To untangle the structure of the resulting cross-correlation map, we decompose the limb of the planet into four sectors, and we analyse each of their contributions separately. Our experiments demonstrate that the cross-correlation signal of an ultra-hot Jupiter is primarily driven by its temperature structure, rotation, and dynamics, while being less sensitive to the precise distribution of iron across the atmosphere. We also show that the previously published iron signal of WASP-76b can be reproduced by a model featuring iron condensation on the leading limb. Alternatively, the signal may be explained by a substantial temperature asymmetry between the trailing and leading limb, where iron condensation is not strictly required to match the data. Finally, we compute the Kp–Vsys maps of the simulated WASP-76b atmospheres, and we show that rotation and dynamics can lead to multiple peaks that are displaced from zero in the planetary rest frame.
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LaCasce, J. H., R. Ferrari, J. Marshall, R. Tulloch, D. Balwada, and K. Speer. "Float-Derived Isopycnal Diffusivities in the DIMES Experiment." Journal of Physical Oceanography 44, no. 2 (February 1, 2014): 764–80. http://dx.doi.org/10.1175/jpo-d-13-0175.1.
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Abstract As part of the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES), 210 subsurface floats were deployed west of the Drake Passage on two targeted density surfaces. Absolute (single particle) diffusivities are calculated for the floats. The focus is on the meridional component, which is less affected by the mean shear. The diffusivities are estimated in several ways, including a novel method based on the probability density function of the meridional displacements. This allows the determination of the range of possible lateral diffusivities, as well as the period over which the spreading can be said to be diffusive. The method is applied to the float data and to synthetic trajectories generated with the Massachusetts Institute of Technology General Circulation Model (MITgcm). Because of ballasting problems, many of the floats did not remain on their targeted density surface. However, the float temperature records suggest that most occupied a small range of densities, so the floats were grouped together for the analysis. The latter focuses on a subset of 109 of the floats, launched near 105°W. The different methods yield a consistent estimate for the diffusivity of 800 ± 200 m2 s−1. The same calculations were made with model particles deployed on 20 different density surfaces and the result for the particles deployed on the neutral density surface γ = 27.7 surface was the same within the errors. The model was then used to map the variation of the diffusivity in the vertical, near the core of the Antarctic Circumpolar Current (ACC). The results suggest mixing is intensified at middepths, between 1500 and 2000 m, consistent with several previous studies.
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Fukumori, Ichiro, Patrick Heimbach, Rui M. Ponte, and Carl Wunsch. "A Dynamically Consistent, Multivariable Ocean Climatology." Bulletin of the American Meteorological Society 99, no. 10 (October 2018): 2107–28. http://dx.doi.org/10.1175/bams-d-17-0213.1.
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AbstractA dynamically consistent 20-yr average ocean climatology based on monthly values during the years 1994–2013 has been produced from the most recent state estimate of the Estimating the Circulation and Climate of the Ocean (ECCO) project, globally, top to bottom. The estimate was produced from a least squares fit of a free-running ocean general circulation model to almost all available near-global data. Data coverage in space and time during this period is far more homogeneous than in any earlier interval and includes CTD, elephant seal, and Argo temperature and salinity profiles; sea ice coverage; full altimetric and gravity-field coverage; satellite sea surface temperatures; and the initializing meteorological coverage from the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim). Dominant remaining data inhomogeneity arises from increasing coverage from the Argo profiles from about 2000 to the present. The state estimate exactly satisfies the primitive equations of the free-running Massachusetts Institute of Technology General Circulation Model (MITgcm) at all times and hence produces values satisfying the fundamental conservation laws of energy, freshwater, and so forth, permitting its use for climate change studies. Quantities such as calculated heat content depend upon all observations, not just temperature, for example, altimetric height and meteorological exchanges. Output files are publicly available in Network Common Data Form (netCDF) and MATLAB form and include hydrographic variables, three components of velocity, and pressure at all depths, as well as other variables, including inferred air–sea momentum and buoyancy fluxes, 3D mixing parameters, and sea ice cover.
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Dong, Jihai, Baylor Fox-Kemper, Hong Zhang, and Changming Dong. "The Scale of Submesoscale Baroclinic Instability Globally." Journal of Physical Oceanography 50, no. 9 (September 1, 2020): 2649–67. http://dx.doi.org/10.1175/jpo-d-20-0043.1.
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AbstractThe spatial scale of submesoscales is an important parameter for studies of submesoscale dynamics and multiscale interactions. The horizontal spatial scales of baroclinic, geostrophic-branch mixed layer instabilities (MLI) are investigated globally (without the equatorial or Arctic oceans) based on observations and simulations in the surface and bottom mixed layers away from significant topography. Three high-vertical-resolution boundary layer schemes driven with profiles from a MITgcm global submesoscale-permitting model improve robustness. The fastest-growing MLI wavelength decreases toward the poles. The zonal median surface MLI wavelength is 51–2.9 km when estimated from the observations and from 32, 25, and 27 km to 2.5, 1.2, and 1.1 km under the K-profile parameterization (KPP), Mellor–Yamada (MY), and κ–ε schemes, respectively. The surface MLI wavelength has a strong seasonality with a median value 1.6 times smaller in summer (10 km) than winter (16 km) globally from the observations. The median bottom MLI wavelengths estimated from simulations are 2.1, 1.4, and 0.41 km globally under the KPP, MY, and κ–ε schemes, respectively, with little seasonality. The estimated required ocean model grid spacings to resolve wintertime surface mixed layer eddies are 1.9 km (50% of regions resolved) and 0.92 km (90%) globally. To resolve summertime eddies or MLI seasonality requires grids finer than 1.3 km (50%) and 0.55 km (90%). To resolve bottom mixed layer eddies, grids finer than 257, 178, and 51 m (50%) and 107, 87, and 17 m (90%) are estimated under the KPP, MY, and κ–ε schemes.