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Journal articles on the topic 'Thermohaline variability'

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Author: Grafiati

Published: 11 March 2023

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1

Greatbatch, Richard J., and K. Andrew Peterson. "Interdecadal variability and oceanic thermohaline adjustment." Journal of Geophysical Research: Oceans 101, no. C9 (September 15, 1996): 20467–82. http://dx.doi.org/10.1029/96jc01531.

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2

Ferrari, Raffaele, and Daniel L. Rudnick. "Thermohaline variability in the upper ocean." Journal of Geophysical Research: Oceans 105, no. C7 (July 15, 2000): 16857–83. http://dx.doi.org/10.1029/2000jc900057.

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3

Weaver, Andrew J., Jochem Marotzke, Patrick F. Cummins, and E. S. Sarachik. "Stability and Variability of the Thermohaline Circulation." Journal of Physical Oceanography 23, no. 1 (January 1993): 39–60. http://dx.doi.org/10.1175/1520-0485(1993)023<0039:savott>2.0.co;2.

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4

Latif, M., C. Böning, J. Willebrand, A. Biastoch, J. Dengg, N. Keenlyside, U. Schweckendiek, and G. Madec. "Is the Thermohaline Circulation Changing?" Journal of Climate 19, no. 18 (September 15, 2006): 4631–37. http://dx.doi.org/10.1175/jcli3876.1.

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Abstract Analyses of ocean observations and model simulations suggest that there have been considerable changes in the thermohaline circulation (THC) during the last century. These changes are likely to be the result of natural multidecadal climate variability and are driven by low-frequency variations of the North Atlantic Oscillation (NAO) through changes in Labrador Sea convection. Indications of a sustained THC weakening are not seen during the last few decades. Instead, a strengthening since the 1980s is observed. The combined assessment of ocean hydrography data and model results indicates that the expected anthropogenic weakening of the THC will remain within the range of natural variability during the next several decades.

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5

Zhai, Xiaoming, Helen L. Johnson, and David P. Marshall. "A Simple Model of the Response of the Atlantic to the North Atlantic Oscillation." Journal of Climate 27, no. 11 (May 29, 2014): 4052–69. http://dx.doi.org/10.1175/jcli-d-13-00330.1.

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Abstract The response of an idealized Atlantic Ocean to wind and thermohaline forcing associated with the North Atlantic Oscillation (NAO) is investigated both analytically and numerically in the framework of a reduced-gravity model. The NAO-related wind forcing is found to drive a time-dependent “leaky” gyre circulation that integrates basinwide stochastic wind Ekman pumping and initiates low-frequency variability along the western boundary. This is subsequently communicated, together with the stochastic variability induced by thermohaline forcing at high latitudes, to the remainder of the Atlantic via boundary and Rossby waves. At low frequencies, the basinwide ocean heat content changes owing to NAO wind forcing and thermohaline forcing are found to oppose each other. The model further suggests that the recently reported opposing changes of the meridional overturning circulation in the Atlantic subtropical and subpolar gyres between 1950–70 and 1980–2000 may be a generic feature caused by interplay between the NAO wind and thermohaline forcing.

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6

Bensi, Manuel, Vedrana Kovačević, Leonardo Langone, Stefano Aliani, Laura Ursella, Ilona Goszczko, Thomas Soltwedel, et al. "Deep Flow Variability Offshore South-West Svalbard (Fram Strait)." Water 11, no. 4 (April 2, 2019): 683. http://dx.doi.org/10.3390/w11040683.

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Water mass generation and mixing in the eastern Fram Strait are strongly influenced by the interaction between Atlantic and Arctic waters and by the local atmospheric forcing, which produce dense water that substantially contributes to maintaining the global thermohaline circulation. The West Spitsbergen margin is an ideal area to study such processes. Hence, in order to investigate the deep flow variability on short-term, seasonal, and multiannual timescales, two moorings were deployed at ~1040 m depth on the southwest Spitsbergen continental slope. We present and discuss time series data collected between June 2014 and June 2016. They reveal thermohaline and current fluctuations that were largest from October to April, when the deep layer, typically occupied by Norwegian Sea Deep Water, was perturbed by sporadic intrusions of warmer, saltier, and less dense water. Surprisingly, the observed anomalies occurred quasi-simultaneously at both sites, despite their distance (~170 km). We argue that these anomalies may arise mainly by the effect of topographically trapped waves excited and modulated by atmospheric forcing. Propagation of internal waves causes a change in the vertical distribution of the Atlantic water, which can reach deep layers. During such events, strong currents typically precede thermohaline variations without significant changes in turbidity. However, turbidity increases during April–June in concomitance with enhanced downslope currents. Since prolonged injections of warm water within the deep layer could lead to a progressive reduction of the density of the abyssal water moving toward the Arctic Ocean, understanding the interplay between shelf, slope, and deep waters along the west Spitsbergen margin could be crucial for making projections on future changes in the global thermohaline circulation.

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7

Hellmer, H. H. "Variability Of Thermohaline Circulation Under An Ice Shelf." Annals of Glaciology 14 (1990): 338. http://dx.doi.org/10.3189/s0260305500009009.

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The production of Antarctic Bottom Water is mainly influenced by Ice Shelf Water, which is formed through the modification of shelf water masses under huge ice shelves. To simulate this modification a two-dimensional thermohaline circulation model has been developed for a section perpendicular to the ice-shelf edge. Hydrographic data from the Filchner Depression enter into the model as boundary conditions. In the outflow region they also serve as a verification of model results.The standard solution reveals two circulation cells. The dominant one transports shelf water near the bottom toward the grounding line, where it begins to ascend along the inclined ice shelf. The contact with the ice shelf causes melting with a maximum rate of 1.5 m a−1 at the grounding line. Freezing and therefore the accumulation of “sea ice” at the bottom of the ice shelf occurs at the end of the melting zone at a rate on the order of 0.1 ma−1. Both rates are comparable with values estimated or predicted by models concerning ice-shelf dynamics.As one example of model sensitivity to changing boundary conditions, a higher sea-ice production in the southern Weddell Sea, as might be expected for a general climatic cooling event, is assumed. The resultant decrease/ increase in temperature/salinity of the inflow (Western Shelf Water) reduces the circulation under the ice shelf and therefore the outflow of Ice Shelf Water by 40%. The maximum melting and freezing rate decreases by 0.1 ma−1 and 0.01 m a−1, respectively. and the freezing zone shifts toward the grounding line by 100 km.In general the intensity of the circulation cells, the characteristics of Ice Shelf Water, the distribution of melting and freezing zones and the melting and freezing rates differ from the standard results with changing boundary conditions. These are the temperature and salinity of the inflow, the surface temperature at the top, and the extension and morphology of the ice shelf.

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8

Tziperman, Eli, and Petros J. Ioannou. "Transient Growth and Optimal Excitation of Thermohaline Variability." Journal of Physical Oceanography 32, no. 12 (December 2002): 3427–35. http://dx.doi.org/10.1175/1520-0485(2002)032<3427:tgaoeo>2.0.co;2.

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9

Hellmer, H. H. "Variability Of Thermohaline Circulation Under An Ice Shelf." Annals of Glaciology 14 (1990): 338. http://dx.doi.org/10.1017/s0260305500009009.

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The production of Antarctic Bottom Water is mainly influenced by Ice Shelf Water, which is formed through the modification of shelf water masses under huge ice shelves. To simulate this modification a two-dimensional thermohaline circulation model has been developed for a section perpendicular to the ice-shelf edge. Hydrographic data from the Filchner Depression enter into the model as boundary conditions. In the outflow region they also serve as a verification of model results. The standard solution reveals two circulation cells. The dominant one transports shelf water near the bottom toward the grounding line, where it begins to ascend along the inclined ice shelf. The contact with the ice shelf causes melting with a maximum rate of 1.5 m a−1 at the grounding line. Freezing and therefore the accumulation of “sea ice” at the bottom of the ice shelf occurs at the end of the melting zone at a rate on the order of 0.1 ma−1. Both rates are comparable with values estimated or predicted by models concerning ice-shelf dynamics. As one example of model sensitivity to changing boundary conditions, a higher sea-ice production in the southern Weddell Sea, as might be expected for a general climatic cooling event, is assumed. The resultant decrease/ increase in temperature/salinity of the inflow (Western Shelf Water) reduces the circulation under the ice shelf and therefore the outflow of Ice Shelf Water by 40%. The maximum melting and freezing rate decreases by 0.1 ma−1 and 0.01 m a−1, respectively. and the freezing zone shifts toward the grounding line by 100 km. In general the intensity of the circulation cells, the characteristics of Ice Shelf Water, the distribution of melting and freezing zones and the melting and freezing rates differ from the standard results with changing boundary conditions. These are the temperature and salinity of the inflow, the surface temperature at the top, and the extension and morphology of the ice shelf.

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10

Lehmann, Andreas, and Hans-Harald Hinrichsen. "On the thermohaline variability of the Baltic Sea." Journal of Marine Systems 25, no. 3-4 (July 2000): 333–57. http://dx.doi.org/10.1016/s0924-7963(00)00026-9.

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11

Zanna, Laure, and Eli Tziperman. "Optimal Surface Excitation of the Thermohaline Circulation." Journal of Physical Oceanography 38, no. 8 (August 1, 2008): 1820–30. http://dx.doi.org/10.1175/2008jpo3752.1.

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Abstract The amplification of thermohaline circulation (THC) anomalies resulting from heat and freshwater forcing at the ocean surface is investigated in a zonally averaged coupled ocean–atmosphere model. Optimal initial conditions of surface temperature and salinity leading to the largest THC growth are computed, and so are the structures of stochastic surface temperature and salinity forcing that excite maximum THC variance (stochastic optimals). When the THC amplitude is defined as its sum of squares (equivalent to using the standard L2 norm), the nonnormal linearized dynamics lead to an amplification with a time scale on the order of 100 yr. The optimal initial conditions have a vanishing THC anomaly, and the complex amplification mechanism involves the advection of both temperature and salinity anomalies by the mean flow and of the mean temperature and salinity by the anomaly flow. The L2 characterization of THC anomalies leads to physically interesting results, yet to a mathematically singular problem. A novel alternative characterizing the THC amplitude by its maximum value, as often done in general circulation model studies, is therefore introduced. This complementary method is shown to be equivalent to using the L-infinity norm, and the needed mathematical approach is developed and applied to the THC problem. Under this norm, an amplification occurs within 10 yr explained by the classic salinity advective feedback mechanism. The analysis of the stochastic optimals shows that the character of the THC variability may be very sensitive to the spatial pattern of the surface forcing. In particular, a maximum THC variance and long-time-scale variability are excited by a basin-scale surface forcing pattern, while a significantly higher frequency and to some extent a weaker variability are induced by a smooth and large-scale, yet mostly concentrated in polar areas, surface forcing pattern. Overall, the results suggest that a large THC variability can be efficiently excited by atmospheric surface forcing, and the simple model used here makes several predictions that would be interesting to test using more complex models.

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12

Latif, M., M. Collins, H. Pohlmann, and N. Keenlyside. "A Review of Predictability Studies of Atlantic Sector Climate on Decadal Time Scales." Journal of Climate 19, no. 23 (December 1, 2006): 5971–87. http://dx.doi.org/10.1175/jcli3945.1.

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Abstract This review paper discusses the physical basis and the potential for decadal climate predictability over the Atlantic and its adjacent land areas. Many observational and modeling studies describe pronounced decadal and multidecadal variability in the Atlantic Ocean. However, it still needs to be quantified to which extent the variations in the ocean drive variations in the atmosphere and over land. In particular, although a clear impact of the Tropics on the midlatitudes has been demonstrated, it is unclear if and how the extratropical atmosphere responds to midlatitudinal sea surface temperature anomalies. Although the mechanisms behind the decadal to multidecadal variability in the Atlantic sector are still controversial, there is some consensus that some of the longer-term multidecadal variability is driven by variations in the thermohaline circulation. The variations in the North Atlantic thermohaline circulation appear to be predictable one to two decades ahead, as shown by a number of perfect model predictability experiments. The next few decades will be dominated by these multidecadal variations, although the effects of anthropogenic climate change are likely to introduce trends. Some impact of the variations of the thermohaline circulation on the atmosphere has been demonstrated in some studies so that useful decadal predictions with economic benefit may be possible.

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13

Silva, Brenno J., Felipe L. Gaspar, Pedro Tyaquiçã, Nathalie Lefèvre, and Manuel J. Flores Montes. "Carbon chemistry variability around a tropical archipelago." Marine and Freshwater Research 70, no. 6 (2019): 767. http://dx.doi.org/10.1071/mf18011.

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Oceanic islands affect the surrounding oceanic circulation by producing upwelling or vortices, resulting in the rising of a richer and colder subsurface water mass. This process increases primary production and can change some biogeochemical processes, such as carbon chemistry and the biological pump. The aim of this study was to describe the vertical variability of carbon chemistry around Fernando de Noronha Archipelago (FNA) and to verify how the island mass effect (IME) can affect carbon distribution. Two transects on opposite sides of the FNA were established according to the direction of the central South Equatorial Current, and samples were collected in July 2010, September 2012 and July 2014 from the surface down to a depth of 500m. The results showed strong stratification, with an uplift of the thermohaline structure, which resulted in an increase of chlorophyll-a concentration downstream of the island during the 2010 and 2014 cruises. Carbon chemistry parameters were strongly correlated with temperature, salinity and dissolved oxygen along the water column and did not change between sides of the island in the periods studied. We conclude that the IME did not significantly affect carbon chemistry, which was more correlated with thermohaline gradient.

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14

Yang, Jiayan, and J. David Neelin. "Decadal Variability in Coupled Sea-Ice–Thermohaline Circulation Systems*." Journal of Climate 10, no. 12 (December 1997): 3059–76. http://dx.doi.org/10.1175/1520-0442(1997)010<3059:dvicsi>2.0.co;2.

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15

Fanning, Augustus F., and Andrew J. Weaver. "Thermohaline Variability: The Effects of Horizontal Resolution and Diffusion." Journal of Climate 11, no. 4 (April 1998): 709–15. http://dx.doi.org/10.1175/1520-0442(1998)011<0709:tvteoh>2.0.co;2.

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16

Lorenzo, María N., Juan J. Taboada, and Isabel Iglesias. "Sensitivity of thermohaline circulation to decadal and multidecadal variability." ICES Journal of Marine Science 66, no. 7 (March 28, 2009): 1439–47. http://dx.doi.org/10.1093/icesjms/fsp061.

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Abstract Lorenzo, M. N., Taboada, J. J., and Iglesias, I. 2009. Sensitivity of thermohaline circulation to decadal and multidecadal variability. – ICES Journal of Marine Science, 66: 1439–1447. In this paper, stochastic freshwater inputs with different variabilities are introduced into an Earth Model of Intermediate Complexity to study their effect on the behaviour of the thermohaline circulation (THC). The variability in the stochastic signal was set to be either decadal or multidecadal (70 years), based on intensity modulation of the El Niño-Southern Oscillation (ENSO) phenomenon. The results demonstrate a weakening of the THC in both the decadal and the multidecadal cases. This weakening results in a reduction in air surface temperature, mainly in the North Atlantic. Moreover, the 500-mb stream function also weakens. This causes lower rainfall in Western Europe, except in the areas most influenced by the Gulf Stream. Sea surface temperature is reduced significantly in the area around Greenland, whereas sea surface salinity is reduced around Greenland and in the Gulf Stream, but increased in the Labrador Sea and in Hudson Strait. The latter effects are more marked in the case where the variability of the inputs is multidecadal. The main implication of these results is that the natural decadal or multidecadal variability in freshwater inputs could have noticeable effects on the fate of the THC, which may be superimposed on the effects of climate change.

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17

Moroz, V. V., and K. T. Bogdanov. "Variability of thermohaline fields in the East China Sea." Oceanology 47, no. 2 (April 2007): 154–60. http://dx.doi.org/10.1134/s0001437007020026.

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18

Zhou, Tianjun, Xuehong Zhang, and Shaowu Wang. "The relationship between the thermohaline circulation and climate variability." Chinese Science Bulletin 45, no. 11 (June 2000): 1052–56. http://dx.doi.org/10.1007/bf02884990.

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19

Timmermann, A., M. Latif, R. Voss, and A. Grötzner. "Northern Hemispheric Interdecadal Variability: A Coupled Air–Sea Mode." Journal of Climate 11, no. 8 (August 1, 1998): 1906–31. http://dx.doi.org/10.1175/1520-0442-11.8.1906.

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Abstract A coupled air–sea mode in the Northern Hemisphere with a period of about 35 years is described. The mode was derived from a multicentury integration with a coupled ocean–atmosphere general circulation model and involves interactions of the thermohaline circulation with the atmosphere in the North Atlantic and interactions between the ocean and the atmosphere in the North Pacific. The authors focus on the physics of the North Atlantic interdecadal variability. If, for instance, the North Atlantic thermohaline circulation is anomalously strong, the ocean is covered by positive sea surface temperature (SST) anomalies. The atmospheric response to these SST anomalies involves a strengthened North Atlantic Oscillation, which leads to anomalously weak evaporation and Ekman transport off Newfoundland and in the Greenland Sea, and the generation of negative sea surface salinity (SSS) anomalies. These SSS anomalies weaken the deep convection in the oceanic sinking regions and subsequently the strength of the thermohaline circulation. This leads to a reduced poleward heat transport and the formation of negative SST anomalies, which completes the phase reversal. The Atlantic and Pacific Oceans seem to be coupled via an atmospheric teleconnection pattern and the interdecadal Northern Hemispheric climate mode is interpreted as an inherently coupled air–sea mode. Furthermore, the origin of the Northern Hemispheric warming observed recently is investigated. The observed temperatures are compared to a characteristic warming pattern derived from a greenhouse warming simulation with the authors’ coupled general circulation model and also with the Northern Hemispheric temperature pattern associated with the 35-yr climate mode. It is shown that the recent Northern Hemispheric warming projects well onto the temperature pattern of the interdecadal mode under consideration.

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20

Taboada, J. J., and M. N. Lorenzo. "Effects of the synoptic scale variability on the thermohaline circulation." Nonlinear Processes in Geophysics 12, no. 4 (March 24, 2005): 435–39. http://dx.doi.org/10.5194/npg-12-435-2005.

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Abstract. In this paper the effect of the synoptic scale variability is analyzed using a simple atmosphere-ocean coupled model. This high frequency variability has been taken into account in the model adding white gaussian noise in variables related to zonal and meridional temperature differences. Results show that synoptic scale frequency variability on longitudinal heating contrast between land and sea can produce a collapse of thermohaline circulation when a threshold of noise is overcome. This result is significant because if synoptic scale variability in the next century increases due to the climatic change an increment of the probability of this collapse could be produced.

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21

Abshagen, Jan, and Axel Timmermann. "An Organizing Center for Thermohaline Excitability." Journal of Physical Oceanography 34, no. 12 (December 1, 2004): 2756–60. http://dx.doi.org/10.1175/jpo2642.1.

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Abstract The bifurcation behavior of a conceptual heat–salt oscillator model is analyzed by means of numerical continuation methods. A global (homoclinic) bifurcation acts as an organizing center for the dynamics of the simplified convective model. It originates from a codimension-2 bifurcation in an extended parameter space. Comparison with earlier work by Cessi shows that the intriguing stochastic thermohaline excitability can be understood from the bifurcation structure of the model. It is argued that global bifurcations may play a crucial role in determining long-term variability of the thermohaline circulation.

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22

Dijkstra, Henk A., and Anna von der Heydt. "Localization of Multidecadal Variability. Part II: Spectral Origin of Multidecadal Modes." Journal of Physical Oceanography 37, no. 10 (October 1, 2007): 2415–28. http://dx.doi.org/10.1175/jpo3135.1.

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Abstract In a companion paper, the authors have shown that in an idealized Atlantic–Pacific Ocean configuration with a conveyor-type overturning circulation, localized multidecadal variability occurs in the Atlantic. Results suggest that the multidecadal variability originates from the instability of the three-dimensional thermohaline circulation and that the physics of the spatial patterns of the SST anomalies can be understood from a study of an Atlantic-only configuration. Specific internal (multidecadal) modes, which obtain a positive growth factor depending on the background thermohaline flow, are associated with the instability. In this paper, the spectral origin of these internal modes is studied using eigensolution continuation techniques. As in the single-hemispheric case, multidecadal modes arise through mergers of so-called SST modes. In the double-hemispheric case studied here, there actually are two types of multidecadal modes that lead to oscillatory behavior. Depending on the background conditions, one of these oscillatory flows is preferred.

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23

Biastoch, Arne, Claus W. Böning, Julia Getzlaff, Jean-Marc Molines, and Gurvan Madec. "Causes of Interannual–Decadal Variability in the Meridional Overturning Circulation of the Midlatitude North Atlantic Ocean." Journal of Climate 21, no. 24 (December 15, 2008): 6599–615. http://dx.doi.org/10.1175/2008jcli2404.1.

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Abstract The causes and characteristics of interannual–decadal variability of the meridional overturning circulation (MOC) in the North Atlantic are investigated with a suite of basin-scale ocean models [the Family of Linked Atlantic Model Experiments (FLAME)] and global ocean–ice models (ORCA), varying in resolution from medium to eddy resolving (½°–1/12°), using various forcing configurations built on bulk formulations invoking atmospheric reanalysis products. Comparison of the model hindcasts indicates similar MOC variability characteristics on time scales up to a decade; both model architectures also simulate an upward trend in MOC strength between the early 1970s and mid-1990s. The causes of the MOC changes are examined by perturbation experiments aimed selectively at the response to individual forcing components. The solutions emphasize an inherently linear character of the midlatitude MOC variability by demonstrating that the anomalies of a (non–eddy resolving) hindcast simulation can be understood as a superposition of decadal and longer-term signals originating from thermohaline forcing variability, and a higher-frequency wind-driven variability. The thermohaline MOC signal is linked to the variability in subarctic deep-water formation, and rapidly progressing to the tropical Atlantic. However, throughout the subtropical and midlatitude North Atlantic, this signal is effectively masked by stronger MOC variability related to wind forcing and, especially north of 30°–35°N, by internally induced (eddy) fluctuations.

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24

Lyons, Joy E., David L. Bradley, R. Lee Culver, and Kyle M. Becker. "The effect of medium variability on acoustic variability: Internal waves and thermohaline intrusions (spice)." Journal of the Acoustical Society of America 119, no. 5 (May 2006): 3428. http://dx.doi.org/10.1121/1.4786879.

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25

Johnson, Helen L., and David P. Marshall. "A Theory for the Surface Atlantic Response to Thermohaline Variability." Journal of Physical Oceanography 32, no. 4 (April 2002): 1121–32. http://dx.doi.org/10.1175/1520-0485(2002)032<1121:atftsa>2.0.co;2.

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26

Pasquero, Claudia, and Eli Tziperman. "Effects of a Wind-Driven Gyre on Thermohaline Circulation Variability." Journal of Physical Oceanography 34, no. 4 (April 2004): 805–16. http://dx.doi.org/10.1175/1520-0485(2004)034<0805:eoawgo>2.0.co;2.

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27

Cai, Wenju, and Stuart J. Godfrey. "Surface heat flux parameterizations and the variability of thermohaline circulation." Journal of Geophysical Research 100, no. C6 (1995): 10679. http://dx.doi.org/10.1029/95jc00587.

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28

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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29

Delworth, Thomas L., and Richard J. Greatbatch. "Multidecadal Thermohaline Circulation Variability Driven by Atmospheric Surface Flux Forcing." Journal of Climate 13, no. 9 (May 2000): 1481–95. http://dx.doi.org/10.1175/1520-0442(2000)013<1481:mtcvdb>2.0.co;2.

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30

L'Hégaret, P., R. Duarte, X. Carton, C. Vic, D. Ciani, R. Baraille, and S. Corréard. "Mesoscale variability in the Arabian Sea from HYCOM model results and observations: impact on the Persian Gulf Water path." Ocean Science Discussions 12, no. 2 (March 12, 2015): 493–550. http://dx.doi.org/10.5194/osd-12-493-2015.

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Abstract. The Arabian Sea and Sea of Oman circulation and water masses, subject to the monsoon forcing, reveal a strong seasonal variability and intense mesoscale features. We describe and analyse this variability and these features, using both meteorological data (from ECMWF reanalyses), in-situ observations (from the ARGO float program and the GDEM climatology), satellite altimetry (from AVISO) and a regional simulation with a primitive equation model (HYCOM). The EOFs of the seasonal variability of the water masses quantify their main changes in thermohaline characteristics and in position. The model and observations display comparable variability, and the model is then used to analyse the three-dimensional structure of eddies and water masses with a higher resolution. The mesoscale eddies have a deep dynamical influence and strongly drive the water masses at depth. In particular, in the Sea of Oman, the Persian Gulf Water presents several offshore ejection sites and a complex recirculation, depending on the mesoscale eddies. This water mass is also captured inside the eddies via several mechanisms, keeping high thermohaline characteristics in the Arabian Sea. These characteristics are validated on the GOGP99 cruise data.

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31

Vilibić, Ivica, Petra Zemunik, Jadranka Šepić, Natalija Dunić, Oussama Marzouk, Hrvoje Mihanović, Clea Denamiel, Robert Precali, and Tamara Djakovac. "Present climate trends and variability in thermohaline properties of the northern Adriatic shelf." Ocean Science 15, no. 5 (October 17, 2019): 1351–62. http://dx.doi.org/10.5194/os-15-1351-2019.

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Abstract. The paper documents seasonality, interannual-to-decadal variability, and trends in temperature, salinity, and density over a transect in the shallow northern Adriatic Sea (Mediterranean Sea) between 1979 and 2017. The amplitude of seasonality decreases with depth and is much larger in temperature and density than in salinity. Time series of temperature and salinity are correlated in the surface but not in the bottom layer. Trends in temperature are large (up to 0.6 ∘C over 10 years), significant through the area, and not sensitive to the sampling interval and time series length. In contrast, trends in salinity are largely small and insignificant and depend on the time series length. The warming of the area is more during spring and summer. Such large temperature trends and their spatial variability emphasize the importance of maintaining regular long-term observations for the proper estimation of thermohaline trends and their variability. This is particularly important in regions which are key for driving thermohaline circulation such as the northern Adriatic, with the potential to affect biogeochemical and ecological properties of the whole Adriatic Sea.

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32

Spall, Michael A. "Thermally Forced Transients in the Thermohaline Circulation." Journal of Physical Oceanography 45, no. 11 (November 2015): 2820–35. http://dx.doi.org/10.1175/jpo-d-15-0101.1.

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AbstractThe response of a convective ocean basin to variations in atmospheric temperature is explored using numerical models and theory. The results indicate that the general behavior depends strongly on the frequency at which the atmosphere changes relative to the local response time to air–sea heat flux. For high-frequency forcing, the convective region in the basin interior is essentially one-dimensional and responds to the integrated local surface heat flux anomalies. For low-frequency forcing, eddy fluxes from the boundary current into the basin interior become important and act to suppress variability forced by the atmosphere. A theory is developed to quantify this time-dependent response and its influence on various oceanic quantities. The amplitude and phase of the temperature and salinity of the convective water mass, the meridional overturning circulation, the meridional heat flux, and the air–sea heat flux predicted by the theory compare well with that diagnosed from a series of numerical model calculations in both strongly eddying and weakly eddying regimes. Linearized analytic solutions provide direct estimates of each of these quantities and demonstrate their dependence on the nondimensional numbers that characterize the domain and atmospheric forcing. These results highlight the importance of mesoscale eddies in modulating the mean and time-dependent ocean response to atmospheric variability and provide a dynamical framework with which to connect ocean observations with changes in the atmosphere and surface heat flux.

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33

Groeskamp, Sjoerd, Jan D. Zika, Trevor J. McDougall, Bernadette M. Sloyan, and Frédéric Laliberté. "The Representation of Ocean Circulation and Variability in Thermodynamic Coordinates." Journal of Physical Oceanography 44, no. 7 (July 1, 2014): 1735–50. http://dx.doi.org/10.1175/jpo-d-13-0213.1.

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Abstract The ocean’s circulation is analyzed in Absolute Salinity SA and Conservative Temperature Θ coordinates. It is separated into 1) an advective component related to geographical displacements in the direction normal to SA and Θ isosurfaces and 2) into a local component, related to local changes in SA–Θ values, without a geographical displacement. In this decomposition, the sum of the advective and local components of the circulation is equivalent to the material derivative of SA and Θ. The sum is directly related to sources and sinks of salt and heat. The advective component is represented by the advective thermohaline streamfunction . After removing a trend, the local component can be represented by the local thermohaline streamfunction . Here, can be diagnosed using a monthly averaged time series of SA and Θ from an observational dataset. In addition, and are determined from a coupled climate model. The diathermohaline streamfunction is the sum of and and represents the nondivergent diathermohaline circulation in SA–Θ coordinates. The diathermohaline trend, resulting from the trend in the local changes of SA and Θ, quantifies the redistribution of the ocean’s volume in SA–Θ coordinates over time. It is argued that the diathermohaline streamfunction provides a powerful tool for the analysis of and comparison among ocean models and observation-based gridded climatologies.

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34

Kim, Who M., Stephen Yeager, and Gokhan Danabasoglu. "Atlantic Multidecadal Variability and Associated Climate Impacts Initiated by Ocean Thermohaline Dynamics." Journal of Climate 33, no. 4 (February 15, 2020): 1317–34. http://dx.doi.org/10.1175/jcli-d-19-0530.1.

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AbstractThe sea surface temperature (SST) signature of Atlantic multidecadal variability (AMV) is a key driver of climate variability in surrounding regions. Low-frequency Atlantic meridional overturning circulation (AMOC) variability is often invoked as a key driving mechanism of AMV-related SST anomalies. However, the origins of both AMV and multidecadal AMOC variability remain areas of active research and debate. Here, using coupled ensemble experiments designed to isolate the climate response to buoyancy forcing associated with the North Atlantic Oscillation in the Labrador Sea, we show that ocean dynamical changes are the essential drivers of AMV and related climate impacts. Atmospheric teleconnections also play an important role in rendering the full AMV pattern by transmitting the ocean-driven subpolar SST signal into the rest of the basin, including the tropical North Atlantic. As such, the atmosphere response to the tropical AMV in our experiments is limited to a relatively small area in the Atlantic sector in summertime, suggesting that it could be overestimated in widely adopted protocols for AMV pacemaker experiments.

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35

Tuzhilkin, Valentin. "SOME FEATURES OF THE BLACK SEA SEASONAL THERMOHALINE VARIABILITY: MODERN VIEW." GEOGRAPHY, ENVIRONMENT, SUSTAINABILITY 3, no. 2 (January 1, 2010): 42–50. http://dx.doi.org/10.24057/2071-9388-2010-3-2-42-50.

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36

Tuzhilkin, Valentin. "SOME FEATURES OF THE BLACK SEA SEASONAL THERMOHALINE VARIABILITY: MODERN VIEW." GEOGRAPHY, ENVIRONMENT, SUSTAINABILITY 3, no. 2 (September 22, 2010): 42–50. http://dx.doi.org/10.15356/2071-9388_02v03_2010_03.

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37

Huang, Rui Xin. "Thermohaline circulation: Energetics and variability in a single-hemisphere basin model." Journal of Geophysical Research 99, no. C6 (1994): 12471. http://dx.doi.org/10.1029/94jc00522.

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38

Chen, Fei, and Michael Ghil. "Interdecadal Variability of the Thermohaline Circulation and High-Latitude Surface Fluxes." Journal of Physical Oceanography 25, no. 11 (November 1995): 2547–68. http://dx.doi.org/10.1175/1520-0485(1995)025<2547:ivottc>2.0.co;2.

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39

te Raa, Lianke A., and Henk A. Dijkstra. "Modes of internal thermohaline variability in a single-hemispheric ocean basin." Journal of Marine Research 61, no. 4 (July 1, 2003): 491–516. http://dx.doi.org/10.1357/002224003322384906.

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40

Piotrowski, Alexander M., Steven L. Goldstein, Sidney R. Hemming, and Richard G. Fairbanks. "Intensification and variability of ocean thermohaline circulation through the last deglaciation." Earth and Planetary Science Letters 225, no. 1-2 (August 2004): 205–20. http://dx.doi.org/10.1016/j.epsl.2004.06.002.

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41

Sun, Che, and Xiao Ma. "Estimating thermohaline variability of the equatorial Pacific Ocean from satellite altimetry." Science China Earth Sciences 59, no. 11 (September 26, 2016): 2213–22. http://dx.doi.org/10.1007/s11430-016-0048-2.

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42

Nair, Nimmi R., K. Anilkumar, and N. Mohan Kumar. "Quantification of Acoustic Variability from Thermohaline Fields in the Arabian Sea." Aquatic Procedia 4 (2015): 466–72. http://dx.doi.org/10.1016/j.aqpro.2015.02.061.

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43

Cheng, W., R. Bleck, and C. Rooth. "Multi-decadal thermohaline variability in an ocean–atmosphere general circulation model." Climate Dynamics 22, no. 6-7 (March 26, 2004): 573–90. http://dx.doi.org/10.1007/s00382-004-0400-6.

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44

Pauthenet, Etienne, Fabien Roquet, Gurvan Madec, and David Nerini. "A Linear Decomposition of the Southern Ocean Thermohaline Structure." Journal of Physical Oceanography 47, no. 1 (January 2017): 29–47. http://dx.doi.org/10.1175/jpo-d-16-0083.1.

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AbstractThe thermohaline structure of the Southern Ocean is deeply influenced by the presence of the Antarctic Circumpolar Current (ACC), where water masses of the World Ocean are advected, transformed, and redistributed to the other basins. It remains a challenge to describe and visualize the complex 3D pattern of this circulation and its associated tracer distribution. Here, a simple framework is presented to analyze the Southern Ocean thermohaline structure. A functional principal component analysis (PCA) is applied to temperature θ and salinity S profiles to determine the main spatial patterns of their variations. Using the Southern Ocean State Estimate (SOSE), this study determines the vertical modes describing the Southern Ocean thermohaline structure between 5 and 2000 m. The first two modes explain 92% of the combined θ–S variance, thus providing a surprisingly good approximation of the thermohaline properties in the Southern Ocean. The first mode (72% of total variance) accurately describes the north–south property gradients. The second mode (20%) mostly describes salinity at 500 m in the region of Antarctic Intermediate Water formation. These two modes present circumpolar patterns that can be closely related with standard frontal definitions. By projecting any given hydrographic profile onto the SOSE-based modes, it is possible to determine its position relative to the fronts. The projection is successfully applied on the hydrographic profiles of the WOCE SR3 section. The Southern Ocean thermohaline decomposition provides an objective way to define water mass boundaries and their spatial variability and has useful application for comparing model output with observations.

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45

Timmermann, A., S.-I. An, U. Krebs, and H. Goosse. "ENSO Suppression due to Weakening of the North Atlantic Thermohaline Circulation*." Journal of Climate 18, no. 16 (August 15, 2005): 3122–39. http://dx.doi.org/10.1175/jcli3495.1.

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Abstract Changes of the North Atlantic thermohaline circulation (THC) excite wave patterns that readjust the thermocline globally. This paper examines the impact of a freshwater-induced THC shutdown on the depth of the Pacific thermocline and its subsequent modification of the El Niño–Southern Oscillation (ENSO) variability using an intermediate-complexity global coupled atmosphere–ocean–sea ice model and an intermediate ENSO model, respectively. It is shown by performing a numerical eigenanalysis and transient simulations that a THC shutdown in the North Atlantic goes along with reduced ENSO variability because of a deepening of the zonal mean tropical Pacific thermocline. A transient simulation also exhibits abrupt changes of ENSO behavior, depending on the rate of THC change. The global oceanic wave adjustment mechanism is shown to play a key role also on multidecadal time scales. Simulated multidecadal global sea surface temperature (SST) patterns show a large degree of similarity with previous climate reconstructions, suggesting that the observed pan-oceanic variability on these time scales is brought about by oceanic waves and by atmospheric teleconnections.

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46

Cardin, V., G. Civitarese, D. Hainbucher, M. Bensi, and A. Rubino. "Thermohaline properties in the Eastern Mediterranean in the last three decades: is the basin returning to the pre-EMT situation?" Ocean Science 11, no. 1 (January 9, 2015): 53–66. http://dx.doi.org/10.5194/os-11-53-2015.

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Abstract. Temperature, salinity and oxygen data collected during April and June 2011 (M84/3 and P414 cruises respectively) are analysed to derive the oceanographic characteristics of the Eastern Mediterranean (EM) basin. These observed characteristics are compared with those from previous cruises over the period 1987–2011. As a result, the interannual and decadal variability of the EM thermohaline properties are discussed in the context of the evolution of the Eastern Mediterranean Transient (EMT) and of the general circulation of the basin. We found that the state of the EM is still far from the pre-EMT conditions, though the 2011 results possibly indicate a slow return to this status. In particular, a comparison between thermohaline property evolution deriving from interannual variability of the preconditioning and air–sea interaction (heat fluxes) in the South Adriatic and the Cretan Seas reveals aspects of the alternation of the two dense water sources (Adriatic and Aegean) during the last three decades, which have strong implications for the hydrographic characteristics of the intermediate and deep layers of the Ionian and Levantine basins.

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47

Rasouli, Kabir, Bouchra R. Nasri, Armina Soleymani, Taufique H. Mahmood, Masahiro Hori, and Ali Torabi Haghighi. "Forecast of streamflows to the Arctic Ocean by a Bayesian neural network model with snowcover and climate inputs." Hydrology Research 51, no. 3 (March 27, 2020): 541–61. http://dx.doi.org/10.2166/nh.2020.164.

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Abstract Increasing water flowing into the Arctic Ocean affects oceanic freshwater balance, which may lead to the thermohaline circulation collapse and unpredictable climatic conditions if freshwater inputs continue to increase. Despite the crucial role of ocean inflow in the climate system, less is known about its predictability, variability, and connectivity to cryospheric and climatic patterns on different time scales. In this study, multi-scale variation modes were decomposed from observed daily and monthly snowcover and river flows to improve the predictability of Arctic Ocean inflows from the Mackenzie River Basin in Canada. Two multi-linear regression and Bayesian neural network models were used with different combinations of remotely sensed snowcover, in-situ inflow observations, and climatic teleconnection patterns as predictors. The results showed that daily and monthly ocean inflows are associated positively with decadal snowcover fluctuations and negatively with interannual snowcover fluctuations. Interannual snowcover and antecedent flow oscillations have a more important role in describing the variability of ocean inflows than seasonal snowmelt and large-scale climatic teleconnection. Both models forecasted inflows seven months in advance with a Nash–Sutcliffe efficiency score of ≈0.8. The proposed methodology can be used to assess the variability of the freshwater input to northern oceans, affecting thermohaline and atmospheric circulations.

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48

Dyakonov, Gleb S., and Rashit A. Ibrayev. "Long-term evolution of Caspian Sea thermohaline properties reconstructed in an eddy-resolving ocean general circulation model." Ocean Science 15, no. 3 (May 16, 2019): 527–41. http://dx.doi.org/10.5194/os-15-527-2019.

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Abstract. Decadal variability in Caspian Sea thermohaline properties is investigated using a high-resolution ocean general circulation model including sea ice thermodynamics and air–sea interaction forced by prescribed realistic atmospheric conditions and riverine runoff. The model describes synoptic, seasonal and climatic variations of sea thermohaline structure, water balance, and sea level. A reconstruction experiment was conducted for the period of 1961–2001, covering a major regime shift in the global climate during 1976–1978, which allowed for an investigation of the Caspian Sea response to such significant episodes of climate variability. The model reproduced sea level evolution reasonably well despite the fact that many factors (such as possible seabed changes and insufficiently explored underground water infiltration) were not taken into account in the numerical reconstruction. This supports the hypothesis relating rapid Caspian Sea level rise in 1978–1995 with global climate change, which caused variation in local atmospheric conditions and riverine discharge reflected in the external forcing data used, as is shown in the paper. Other effects of the climatic shift are investigated, including a decrease in salinity in the active layer, strengthening of its stratification and corresponding diminishing of convection. It is also demonstrated that water exchange between the three Caspian basins (northern, middle and southern) plays a crucial role in the formation of their thermohaline regime. The reconstructed long-term trends in seawater salinity (general downtrend after 1978), temperature (overall increase) and density (general downtrend) are studied, including an assessment of the influence of main surface circulation patterns and model error accumulation.

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49

Dong, Buwen, and Rowan T. Sutton. "Mechanism of Interdecadal Thermohaline Circulation Variability in a Coupled Ocean–Atmosphere GCM." Journal of Climate 18, no. 8 (April 15, 2005): 1117–35. http://dx.doi.org/10.1175/jcli3328.1.

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Abstract Interdecadal variability of the Atlantic thermohaline circulation (THC) is studied in the third version of the Hadley Centre global coupled atmosphere–ocean sea-ice general circulation model (HadCM3). A diagnostic approach is used to elucidate the mechanism that governs the variability and its impacts on climate. An irregular and heavily damped THC oscillation with a period around 25 yr is identified. The oscillation appears to be forced by the atmosphere but the ocean is responsible for setting the time scale. Following a minimum in the THC, the mechanism for phase reversal involves the accumulation of cold water in the subpolar gyre, leading to an acceleration of the gyre circulation and the North Atlantic Current. This acceleration increases the transport of saline waters into the regions of active deep convection, raising the upper-ocean density and leading, after adjustment, to acceleration of the THC. The atmosphere stimulates this THC variability in two ways: 1) by forcing the subpolar gyre through (North Atlantic Oscillation) NAO-related wind stress curl and heat flux anomalies; and 2) by direct forcing of the region of active deep convection, also through wind stress curl and heat flux anomalies. The latter is not closely related to the NAO. The mechanism for phase reversal has many similarities to that found in a previous study with a much lower resolution coupled model, suggesting that this mechanism may be quite robust. However the time scale, and details of the atmospheric forcing, differ. The THC variability in HadCM3 has significant impacts on the atmosphere not just in the Atlantic region but also more widely, throughout the global Tropics. The mechanism involves modulation by the THC of the cross-equator SST gradient in the tropical Atlantic. The SST anomalies induce a displacement of the ITCZ in the Atlantic basin with knock-on effects over the other ocean basins. These findings highlight the potential importance of the Atlantic THC as a cause of interdecadal climate variability on a global scale.

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50

Weaver, Andrew J., and Sophie Valcke. "On the Variability of the Thermohaline Circulation in the GFDL Coupled Model." Journal of Climate 11, no. 4 (April 1998): 759–67. http://dx.doi.org/10.1175/1520-0442(1998)011<0759:otvott>2.0.co;2.

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