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1
Zhou, M., Y. Zhu, F. d'Ovidio, Y. H. Park, I. Durand, E. Kestenare, V. Sanial, et al. "Surface currents and upwelling in Kerguelen Plateau regions." Biogeosciences Discussions 11, no. 5 (May 12, 2014): 6845–76. http://dx.doi.org/10.5194/bgd-11-6845-2014.
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Abstract. Mean currents, horizontal diffusivity and upwelling on the Kerguelen Plateau and the deep basin east of the Kerguelen Islands were studied using 48 World Ocean Circulation Experiment (WOCE) Standard Surface Velocity Program (SVP) drifters deployed during the 2011 austral spring KEOPS II (KErguelen Ocean Plateau compared Study II) cruise. These drifter data were analyzed based on autocovariances for temporal scales, least-squares fitted streamfunctions for estimating mesoscale mean currents, wind stress fields and Ekman pumping, and Taylor's single particle diffusivity for estimating horizontal dispersion of surface waters. The results have revealed the shelfbreak current on the southern and eastern shelf slopes of the Kerguelen Islands, transport of surface waters from the Kerguelen–Heard shelf basin crossing the shelf slope into the deep basin off the plateau east of the Kerguelen Islands, and upwelling driven by wind stress curl in both the plateau and deep basin regions. The estimated volume transports off the Plateau in the upper 50 m based on surface drifters and below the mixed layer based on wind stress curl are 0.5 and 1.7 Sv, respectively, the mean and standard deviation of vertical velocities driven by wind stress curl averaged in the plateau and deep basin regions up to 3.2 ± 7.4 m d−1, and the upwelling fluxes in the surveyed plateau and deep basin regions are approximately 0.7 and 1.1 Sv, respectively. These physical transport processes can have significant effects on balances between biogeochemical elements and their recycling processes.
2
Venchiarutti, C., M. Roy-Barman, R. Freydier, P. van Beek, M. Souhaut, and C. Jeandel. "Influence of intense scavenging on Pa-Th fractionation in the wake of Kerguelen Island (Southern Ocean)." Biogeosciences 8, no. 11 (November 8, 2011): 3187–201. http://dx.doi.org/10.5194/bg-8-3187-2011.
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Abstract. Dissolved and particulate excess 230Th and 231Pa concentrations (noted 230Thxs and 231Paxs respectively) and 231Paxs/230Thxs activity ratios were investigated on and out of the Kerguelen plateau (Southern Ocean) in the framework of the Kerguelen Ocean and Plateau compared Study project in order to better understand the influence of particle flux and particle chemistry and advection on the scavenging of 231Pa. In the wake of Kerguelen, particulate 231Paxs is relatively abundant compared to its content in the dissolved phase. This, together with the low fractionation observed between 230Th and 231Pa (FTh/Pa ranging from 0.06 ± 0.01 to 1.6 ± 0.2) reflects the domination of the biogenic silica in the particle pool. Along the eastern escarpment of the Kerguelen plateau, the strong 231Paxs horizontal gradient in the deep waters highlights the intense removal of 231Pa at depth, as already observed for 230Thxs. This local boundary scavenging was attributed to re-suspension of opal-rich particles by nepheloid layers, resulting in fractionation factors FTh/Pa ≤ 1 along the Kerguelen plateau slope. Therefore, both the composition (biogenic opal) and the flux (intense along the margin) of particles control the scavenging of the two radionuclides in the Kerguelen wake. The modelling of 231Pa distribution with an advection-scavenging model demonstrates that lateral advection of open ocean water on the Kerguelen plateau could supply most of the 231Pa, which is then efficiently scavenged on the highly productive plateau, as previously proposed for 230Thxs. It stresses that lateral advection can play a significant role in the overall budget of particle reactive trace elements in a coastal-open ocean system.
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Falvey, David A. "Kerguelen Plateau Research Cruise." Eos, Transactions American Geophysical Union 66, no. 37 (1985): 641. http://dx.doi.org/10.1029/eo066i037p00641-01.
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Venchiarutti, C., M. Roy-Barman, R. Freydier, P. van Beek, M. Souhaut, and C. Jeandel. "Influence of intense scavenging on Pa-Th fractionation in the wake of Kerguelen Island (Southern Ocean)." Biogeosciences Discussions 8, no. 3 (May 17, 2011): 4871–916. http://dx.doi.org/10.5194/bgd-8-4871-2011.
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Abstract. Dissolved and particulate excess 230Th and 231Pa concentrations (noted 230Thxs and 231Paxs, respectively) and 231Paxs/230Thxs activity ratios were investigated on and out of the Kerguelen plateau (Southern Ocean) in the framework of the KErguelen Ocean and Plateau compared Study project in order to better understand the influence of particle flux and particle chemistry and advection on the scavenging of 231Pa. In the wake of Kerguelen Island, the relative abundance of 231Paxs in the particles compared to the dissolved phase associated with a low fractionation factor between 230Th and 231Pa (FTh/Pa ranging from 0.06 ± 0.01 to 2.13 ± 0.63) is consistent with particles being dominated by biogenic silica in this area. Strong 231Pa concentration gradients occur on relatively short distances. Along the eastern escarpment of the Kerguelen plateau, an intensive scavenging affects significantly the dissolved distribution of 231Paxs at depth, as already observed for 230Thxs. This local boundary scavenging was attributed to re-suspension of opal-rich particles by nepheloid layers, resulting in fractionation factors FTh/Pa ≤ 1 along the Kerguelen plateau slope. Therefore, these results showed that in the Kerguelen wake, both the composition (biogenic opal) and the flux (intensive along the margin) of particles control the scavenging of the two radionuclides. The modelling of 231Pa distribution with an advection-scavenging model demonstrate that lateral advection of open ocean water on the Kerguelen plateau could supply most of the 231Pa, which is then efficiently scavenged on the highly productive plateau, as previously proposed for 230Thxs. It stresses that lateral advection can play a significant role in the overall budget of particle reactive trace elements in a coastal-open ocean system.
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Dubinin, E. P., A. A. Shaikhullina, A. A. Bulychev, G. L. Leitchenkov, and A. A. Maksimova. "Structure of the tectonosphere of the Kerguelen plateau margins according to the geological and geophysical data." Moscow University Bulletin. Series 4. Geology, no. 3 (June 28, 2020): 12–24. http://dx.doi.org/10.33623/0579-9406-2020-3-12-24.
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Kerguelen Plateau is the largest underwater rise in the southern Indian Ocean. The heterogeneous structure of the crust, plume magmatic activity, as well as a different ages of adjacent basins — all this indicates a different structure of the marginal zones of the plateau. In this work, on the basis of geological and geophysical information, various morphodynamic types of the margins of the Kerguelen plateau are identified. An analysis of the bottom topography and data of potential fields together with two-dimensional density modeling allows us to specify the deep structure of the tectonosphere of the margins of the Kerguelen plateau and take a fresh look at their nature.
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Lemenkova, Polina. "Seafloor and Ocean Crust Structure of the Kerguelen Plateau from Marine Geophysical and Satellite Altimetry Datasets." Geomatics 3, no. 3 (August 10, 2023): 393–426. http://dx.doi.org/10.3390/geomatics3030022.
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The volcanic Kerguelen Islands are formed on one of the world’s largest submarine plateaus. Located in the remote segment of the southern Indian Ocean close to Antarctica, the Kerguelen Plateau is notable for a complex tectonic origin and geologic formation related to the Cretaceous history of the continents. This is reflected in the varying age of the oceanic crust adjacent to the plateau and the highly heterogeneous bathymetry of the Kerguelen Plateau, with seafloor structure differing for the southern and northern segments. Remote sensing data derived from marine gravity and satellite radar altimetry surveys serve as an important source of information for mapping complex seafloor features. This study incorporates geospatial information from NOAA, EMAG2, WDMAM, ETOPO1, and EGM96 datasets to refine the extent and distribution of the extracted seafloor features. The cartographic joint analysis of topography, magnetic anomalies, tectonic and gravity grids is based on the integrated mapping performed using the Generic Mapping Tools (GMT) programming suite. Mapping of the submerged features (Broken Ridge, Crozet Islands, seafloor fabric, orientation, and frequency of magnetic anomalies) enables analysis of their correspondence with free-air gravity and magnetic anomalies, geodynamic setting, and seabed structure in the southwest Indian Ocean. The results show that integrating the datasets using advanced cartographic scripting language improves identification and visualization of the seabed objects. The results include 11 new maps of the region covering the Kerguelen Plateau and southwest Indian Ocean. This study contributes to increasing the knowledge of the seafloor structure in the French Southern and Antarctic Lands.
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Wang, Jinbo, Matthew R. Mazloff, and Sarah T. Gille. "The Effect of the Kerguelen Plateau on the Ocean Circulation." Journal of Physical Oceanography 46, no. 11 (November 2016): 3385–96. http://dx.doi.org/10.1175/jpo-d-15-0216.1.
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AbstractThe Kerguelen Plateau is a major topographic feature in the Southern Ocean. Located in the Indian sector and spanning nearly 2000 km in the meridional direction from the polar to the subantarctic region, it deflects the eastward-flowing Antarctic Circumpolar Current and influences the physical circulation and biogeochemistry of the Southern Ocean. The Kerguelen Plateau is known to govern the local dynamics, but its impact on the large-scale ocean circulation has not been explored. By comparing global ocean numerical simulations with and without the Kerguelen Plateau, this study identifies two major Kerguelen Plateau effects: 1) The plateau supports a local pressure field that pushes the Antarctic Circumpolar Current northward. This process reduces the warm-water transport from the Indian to the Atlantic Ocean. 2) The plateau-generated pressure field shields the Weddell Gyre from the influence of the warmer subantarctic and subtropical waters. The first effect influences the strength of the Antarctic Circumpolar Current and the Agulhas leakage, both of which are important elements in the global thermohaline circulation. The second effect results in a zonally asymmetric response of the subpolar gyres to Southern Hemisphere wind forcing.
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Bown, J., M. Boye, P. Laan, A. R. Bowie, Y. H. Park, C. Jeandel, and D. M. Nelson. "Imprint of a dissolved cobalt basaltic source on the Kerguelen Plateau." Biogeosciences 9, no. 12 (December 19, 2012): 5279–90. http://dx.doi.org/10.5194/bg-9-5279-2012.
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Abstract. Processes of cobalt (Co) entrainment from shelf sediments over the Kerguelen Plateau were studied during the KEOPS (Kerguelen Ocean Plateau compared Study) in order to explain the exceptionally high dissolved cobalt concentrations that have been measured in the surface waters above the Kerguelen Plateau, and in intermediate and deep waters above its eastern slope. Lateral advection and dissolution of Co contained in basalt sediments around Heard Island, a main source of lithogenic Co in the study area, were shown to imprint the process of surface enrichment over the plateau. Dissolved Co enrichment was strongest at the intercept of the eastern slope with intermediate and deep waters, probably due to more efficient mobilisation of the sediments in the slope current, in addition to advection of Co-enriched and low-oxygenated ocean water masses. In surface waters, the strong sedimentary Co inputs were estimated to be much higher than biological Co uptake in phytoplankton blooms, underlining the potential use of dissolved cobalt as tracer of the natural iron fertilization above the Kerguelen Plateau. Based on a simple steady-state balance equation of the external input of dissolved iron over the plateau, the fertilization of iron inferred by using dissolved Co as a tracer of basalt sources is estimated to be 28 × 102 ± 21 × 102 t yr−1 in surface waters of the Kerguelen Plateau. This estimate is consistent with preceding ones (Zhang et al., 2008; Chever et al., 2010), and the calculated iron supply matches with the phytoplankton demand (Sarthou et al., 2008).
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Bown, J., M. Boye, P. Laan, A. R. Bowie, Y. H. Park, C. Jeandel, and D. M. Nelson. "Imprint of a dissolved cobalt basaltic source on the Kerguelen Plateau." Biogeosciences Discussions 9, no. 6 (June 19, 2012): 7291–312. http://dx.doi.org/10.5194/bgd-9-7291-2012.
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Abstract. Processes of cobalt (Co) entrainment from shelf sediments over the Kerguelen Plateau were studied during the KEOPS (Kerguelen Ocean Plateau compared Study) in order to explain the exceptionally high dissolved cobalt concentrations that have been measured in the surface waters above the Kerguelen Plateau, and in intermediate and deep waters above its eastern slope. Lateral advection and dissolution of Co contained in basalt sediments around Heard Island, a main source of lithogenic Co in the study area, were shown to imprint the process of surface enrichment over the plateau. Dissolved Co enrichment was strongest at the intercept of the eastern slope with intermediate and deep waters, probably due to more efficient mobilisation of the sediments in the slope current, in addition to advection of Co-enriched and low oxygenated ocean water-masses. In surface waters, strong sedimentary Co inputs were estimated to be much higher than biological Co uptake in phytoplankton blooms, underlining the potential role of cobalt as lithogenic tracer. Based on a simple, steady state balance equation of the external input of dissolved iron over the plateau, the fertilization of iron inferred by using Co as a tracer of basalt sources is estimated to be 28 × 102 ± 21 × 102 ton yr−1 in surface waters of the Kerguelen Plateau. This estimate is consistent with preceding ones and the required iron supply matching the phytoplankton demand.
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Quéroué, F., G. Sarthou, H. F. Planquette, E. Bucciarelli, F. Chever, P. van der Merwe, D. Lannuzel, et al. "High variability in dissolved iron concentrations in the vicinity of the Kerguelen Islands (Southern Ocean)." Biogeosciences 12, no. 12 (June 25, 2015): 3869–83. http://dx.doi.org/10.5194/bg-12-3869-2015.
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Abstract. Dissolved Fe (dFe) concentrations were measured in the upper 1300 m of the water column in the vicinity of the Kerguelen Islands as part of the second KErguelen Ocean Plateau compared Study (KEOPS2). Concentrations ranged from 0.06 nmol L−1 in offshore, Southern Ocean waters to 3.82 nmol L−1 within Hillsborough Bay, on the north-eastern coast of the Kerguelen Islands. Direct island runoff, glacial melting and resuspended sediments were identified as important inputs of dFe that could potentially fertilise the northern part of the plateau. A significant deep dFe enrichment was observed over the plateau with dFe concentrations increasing up to 1.30 nmol L−1 close to the seafloor, probably due to sediment resuspension and pore water release. Biological uptake was shown to induce a significant decrease in dFe concentrations between two visits (28 days apart) at a station above the plateau. Our work also considered other processes and sources, such as lateral advection of enriched seawater, remineralisation processes, and the influence of the polar front (PF) as a vector for Fe transport. Overall, heterogeneous sources of Fe over and off the Kerguelen Plateau, in addition to strong variability in Fe supply by vertical or horizontal transport, may explain the high variability in dFe concentrations observed during this study.
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Quéroué, F., G. Sarthou, H. F. Planquette, E. Bucciarelli, F. Chever, P. van der Merwe, D. Lannuzel, et al. "High variability of dissolved iron concentrations in the vicinity of Kerguelen Island (Southern Ocean)." Biogeosciences Discussions 12, no. 1 (January 6, 2015): 231–70. http://dx.doi.org/10.5194/bgd-12-231-2015.
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Abstract. Dissolved Fe (dFe) concentrations were measured in the upper 1300 m of the water column in the vicinity of Kerguelen Island as part of the second Kerguelen Ocean Plateau compared Study (KEOPS2). Concentrations ranged from 0.06 nmol L−1 in offshore, Southern Ocean waters, to 3.82 nmol L−1 within Hillsborough Bay, on the north-eastern coast of Kerguelen Island. Direct island runoff, glacial melting and resuspended sediments were identified as important inputs of dFe that could potentially fertilize the northern part of the plateau. A significant deep dFe enrichment was observed over the plateau with dFe concentrations increasing up to 1.30 nmol L−1 close to the seafloor, probably due to sediment resuspension and pore water release. Biological uptake was identified as a likely explanation for the decrease in dFe concentrations between two visits (28 days apart) at a station above the plateau. Our results allowed studying other processes and sources, such as atmospheric inputs, lateral advection of enriched seawater, remineralization processes and the influence of the Polar Front (PF) as a vector for Fe transport. Overall, heterogeneous sources of Fe over and off the Kerguelen Plateau, in addition to strong variability in Fe supply by vertical or horizontal transport, may explain the high variability in dFe concentrations observed during this study.
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Agranov, G. D., E. P. Dubinin, and A. L. Grokholsky. "Physical modeling of the interaction between the spreading ridge and the large Kerguelen igneous province." Moscow University Bulletin. Series 4. Geology, no. 5 (December 16, 2022): 19–27. http://dx.doi.org/10.33623/0579-9406-2022-5-19-27.
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The problem of the interaction of spreading ridges with large igneous provinces is widely discussed in the scientific literature. The most striking and well-preserved example of such interaction in the geological past is the “collision” of the Southeast Indian spreading ridge and the Kerguelen plateau, which occurred about 43 Maago. The consequence of this event was the division of a single Kerguelen plateau into two parts: in fact, the Kerguelen plateau and the Broken ridge. The conditions for the formation of these morphostructures were studied experimentally. The paper presents the results of modeling the interaction of a spreading ridge with a large igneous province. The experimental results correlate well with geological and geophysical data and with the proposed model for the development of this region.
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Gille, S. T., M. M. Carranza, R. Cambra, and R. Morrow. "Wind-induced upwelling in the Kerguelen Plateau region." Biogeosciences 11, no. 22 (November 26, 2014): 6389–400. http://dx.doi.org/10.5194/bg-11-6389-2014.
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Abstract. In contrast to most of the Southern Ocean, the Kerguelen Plateau supports an unusually strong spring chlorophyll (Chl a) bloom, likely because the euphotic zone in the region is supplied with higher iron concentrations. This study uses satellite wind, sea surface temperature (SST), and ocean color data to explore the impact of wind-driven processes on upwelling of cold (presumably iron-rich) water to the euphotic zone. Results show that, in the Kerguelen region, cold SSTs correlate with high wind speeds, implying that wind-mixing leads to enhanced vertical mixing. Cold SSTs also correlate with negative wind-stress curl, implying that Ekman pumping can further enhance upwelling. In the moderate to high eddy kinetic energy (EKE) regions surrounding Kerguelen, we find evidence of coupling between winds and SST gradients associated with mesoscale eddies, which can locally modulate the wind-stress curl. This coupling introduces persistent wind-stress curl patterns and Ekman pumping around these long-lived eddies, which may modulate the evolution of Chl a in the downstream plume far offshore. Close to the plateau, this eddy coupling breaks down. Kerguelen has a significant wind shadow on its downwind side, which changes position depending on the prevailing wind and which generates a wind-stress curl dipole that shifts location depending on wind direction. This leads to locally enhanced Ekman pumping for a few hundred kilometers downstream from the Kerguelen Plateau; Chl a values tend to be more elevated in places where wind-stress curl induces Ekman upwelling than in locations of downwelling, although the estimated upwelling rates are too small for this relationship to derive from direct effects on upward iron supply, and thus other processes, which remain to be determined, must also be involved in the establishment of these correlations. During the October and November (2011) KErguelen Ocean and Plateau compared Study (KEOPS-2) field program, wind conditions were fairly typical for the region, with enhanced Ekman upwelling expected to the north of the Kerguelen Islands.
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Merlivat, L., J. Boutin, and F. d'Ovidio. "Carbon, oxygen and biological productivity in the Southern Ocean in and out the Kerguelen plume: CARIOCA drifter results." Biogeosciences Discussions 11, no. 12 (December 9, 2014): 16877–909. http://dx.doi.org/10.5194/bgd-11-16877-2014.
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Abstract. The Kerguelen Plateau region in the Indian sector of the Southern Ocean supports annually a large-scale phytoplankton bloom which is naturally fertilized with iron. As part of the second Kerguelen Ocean and Plateau compared Study expedition (KEOPS2) in austral spring (October–November 2011), one Carioca buoy was deployed east of the Kerguelen plateau. It drifted eastward downstream in the Kerguelen plume. Hourly surface measurements of pCO2, O2 and ancillary observations were collected between 1 November 2011 to 12 February 2012 with the aim of characterizing the spatial and temporal variability of the biological Net Community Production (NCP) downstream the Kerguelen plateau, assess the impact of iron-induced productivity on the biological carbon consumption and consequently on the CO2 flux exchanged at the air–sea interface. The trajectory of the buoy until mid-December was within the longitude range, 72–83° E, close to the polar front and then in the polar frontal zone, PFZ, until 97° E. From 17 November to 16 December, the buoy drifted within the Kerguelen plume following a filament carrying dissolved iron, DFe, for a total distance of 700 km. In the first part of the trajectory, the ocean surface waters are a sink for CO2 and a source for CO2, with fluxes of respective mean values equal to −8 and +38 mmol CO2 m−2 d−1. Eastward, as the buoy escapes the iron enriched filament, the fluxes are in opposite direction, with respective mean values of +5 and −48 mmol O2 m−2 d−1. These numbers clearly indicate the strong impact of biological processes on the biogeochemistry in the surface waters within the Kerguelen plume in November-mid-December, while it is undetectable eastward in the PFZ from mid-December to mid-February. While the buoy follows the Fe enriched filament, simultaneous observations of dissolved inorganic carbon, DIC, and dissolved oxygen, O2, highlight biological events lasting from 2 to 4 days. Stoichiometric ratios, O2/C, between 1.1 and 1.4 are observed indicating new and regenerated production regimes. NCP estimates range from 60 to 140 mmol C m−2 d−1. Based on the relationship between the time a water parcel has left the plateau and its iron content, we have highlighted that the main control on the value of NCP is the availability of iron in the upper water column, with the largest NCP occurring in waters that have recently left the plateau and presented the highest iron concentrations.
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Ramsay, D. C., J. B. Colwell, M. F. Coffin, H. L. Davies, P. J. Hill, C. J. Pigram, and H. M. J. Stagg. "New findings from the Kerguelen Plateau." Geology 14, no. 7 (1986): 589. http://dx.doi.org/10.1130/0091-7613(1986)14<589:nfftkp>2.0.co;2.
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Merlivat, L., J. Boutin, and F. d'Ovidio. "Carbon, oxygen and biological productivity in the Southern Ocean in and out the Kerguelen plume: CARIOCA drifter results." Biogeosciences 12, no. 11 (June 9, 2015): 3513–24. http://dx.doi.org/10.5194/bg-12-3513-2015.
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Abstract. The Kerguelen Plateau region in the Indian sector of the Southern Ocean supports annually a large-scale phytoplankton bloom which is naturally fertilized with iron. As part of the second Kerguelen Ocean and Plateau compared Study expedition (KEOPS2) in austral spring (October–November 2011), one CARbon Interface OCean Atmosphere (CARIOCA) buoy was deployed east of the Kerguelen Plateau. It drifted eastward downstream along the Kerguelen plume. Hourly surface measurements of pCO2, O2 and ancillary observations were collected between 1 November 2011 and 12 February 2012 with the aim of characterizing the spatial and temporal variability of the biological net community production, NCP, downstream the Kerguelen Plateau, assessing the impact of iron-induced productivity on the biological inorganic carbon consumption and consequently on the CO2 flux exchanged at the air–sea interface. The trajectory of the buoy up to mid-December was within the longitude range 72–83° E, close to the polar front and then in the polar frontal zone, PFZ, up to 97° E. From 17 November to 16 December, the buoy drifted within the Kerguelen plume following a filament carrying dissolved iron, DFe, for a total distance of 700 km. In the first part of the trajectory of the buoy, within the iron plume, the ocean surface waters were always a sink for CO2 and a source for O2, with fluxes of respective mean values equal to −8 mmol CO2 and +38 mmol O2 m−2 d−1. To the east, as the buoy escaped the iron-enriched filament, the fluxes were in the opposite direction, with respective mean values of +5 mmol CO2 and −48 mmol O2 m−2 d−1. These numbers clearly indicate the strong impact of biological processes on the biogeochemistry in the surface waters within the Kerguelen plume in November–mid-December, while it is undetectable to the east in the PFZ from mid- December to mid-February. While the buoy follows the Fe-enriched filament, simultaneous observations of dissolved inorganic carbon (DIC) and dissolved oxygen (O2) highlight biological events lasting from 2 to 4 days. Stoichiometric ratios, O2 / C, between 1.1 and 1.4 are observed indicating new and regenerated production regimes. NCP estimates range from 60 to 140 mmol C m−2 d−1.
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Gille, S. T., M. M. Carranza, R. Cambra, and R. Morrow. "Wind-induced upwelling in the Kerguelen Plateau Region." Biogeosciences Discussions 11, no. 6 (June 5, 2014): 8373–97. http://dx.doi.org/10.5194/bgd-11-8373-2014.
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Abstract. In contrast to most of the Southern Ocean, the Kerguelen Plateau supports an unusually strong spring chlorophyll (Chl a) bloom, likely because the euphotic zone in the region is supplied with higher iron concentrations. This study uses satellite wind, sea surface temperature (SST), and ocean color data to explore the impact of wind-driven processes on upwelling of cold (presumably iron-rich) water to the euphotic zone. High wind speeds typically correlate with cold sea surface temperatures, implying that wind-mixing leads to enhanced vertical mixing. Negative wind-stress curl also correlates with cold SSTs, implying that Ekman pumping can further enhance upwelling, and coupling between winds and SSTs associated with mesoscale eddies can locally modulate the wind-stress curl. Kerguelen has a significant wind shadow on its downwind side, which generates a wind-stress curl dipole that shifts location depending on wind direction. This leads to locally enhanced Ekman pumping on the downstream side of the Kerguelen Plateau, where Chl a blooms are observed most years.
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Operto, Stéphane, and Philippe Charvis. "Kerguelen Plateau: A volcanic passive margin fragment?" Geology 23, no. 2 (1995): 137. http://dx.doi.org/10.1130/0091-7613(1995)023<0137:kpavpm>2.3.co;2.
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Zhang, Jinchang, Yiming Luo, and Jie Chen. "Oceanic Plateau Formation Implied by Ontong Java Plateau, Kerguelen Plateau and Shatsky Rise." Journal of Ocean University of China 19, no. 2 (September 4, 2019): 351–60. http://dx.doi.org/10.1007/s11802-020-4246-2.
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WALLACE, P. J. "Origin and Evolution of the Kerguelen Plateau, Broken Ridge and Kerguelen Archipelago: Editorial." Journal of Petrology 43, no. 7 (July 1, 2002): 1105–8. http://dx.doi.org/10.1093/petrology/43.7.1105.
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Bergue, Cristianini T., and Abiraman Govindan. "Eocene-Pliocene deep sea ostracodes from ODP site 744A, Southern Indian Ocean." Anais da Academia Brasileira de Ciências 82, no. 3 (September 2010): 747–60. http://dx.doi.org/10.1590/s0001-37652010000300021.
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The Eocene-Pliocene deep sea ostracodes from the ODP site 744A (Kerguelen Plateau) are herein studied under the taxonomic and paleoecologic aspects. 28 species are identified, being the genera Krithe, Cytherella and Dutoitella the most diversified. A faunal threshold was recorded in the Early Oligocene, which is tentatively explained under the knowledge of the paleoceanographical studies carried out not only in the Kerguelen Plateau but also in adjacent areas. The faunal turnover and variations in both richness and abundance possibly reflect the inception of psychrosphere and the influence of hydrological changes in the preservation of carapaces. Moreover, the influence of those changes on carbonate preservation is discussed as the cause of faunal impoverishment in the upper portion of the core.
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Bowie, A. R., P. van der Merwe, F. Quéroué, T. Trull, M. Fourquez, F. Planchon, G. Sarthou, et al. "Iron budgets for three distinct biogeochemical sites around the Kerguelen Archipelago (Southern Ocean) during the natural fertilisation study, KEOPS-2." Biogeosciences 12, no. 14 (July 29, 2015): 4421–45. http://dx.doi.org/10.5194/bg-12-4421-2015.
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Abstract. Iron availability in the Southern Ocean controls phytoplankton growth, community composition and the uptake of atmospheric CO2 by the biological pump. The KEOPS-2 (KErguelen Ocean and Plateau compared Study 2) "process study", took place around the Kerguelen Plateau in the Indian sector of the Southern Ocean. This is a region naturally fertilised with iron on the scale of hundreds to thousands of square kilometres, producing a mosaic of spring blooms which show distinct biological and biogeochemical responses to fertilisation. This paper presents biogeochemical iron budgets (incorporating vertical and lateral supply, internal cycling, and sinks) for three contrasting sites: an upstream high-nutrient low-chlorophyll reference, over the plateau and in the offshore plume east of the Kerguelen Islands. These budgets show that distinct regional environments driven by complex circulation and transport pathways are responsible for differences in the mode and strength of iron supply, with vertical supply dominant on the plateau and lateral supply dominant in the plume. Iron supply from "new" sources (diffusion, upwelling, entrainment, lateral advection, atmospheric dust) to the surface waters of the plume was double that above the plateau and 20 times greater than at the reference site, whilst iron demand (measured by cellular uptake) in the plume was similar to that above the plateau but 40 times greater than at the reference site. "Recycled" iron supply by bacterial regeneration and zooplankton grazing was a relatively minor component at all sites (< 8 % of new supply), in contrast to earlier findings from other biogeochemical iron budgets in the Southern Ocean. Over the plateau, a particulate iron dissolution term of 2.5 % was invoked to balance the budget; this approximately doubled the standing stock of dissolved iron in the mixed layer. The exchange of iron between dissolved, biogenic particulate and lithogenic particulate pools was highly dynamic in time and space, resulting in a decoupling of the iron supply and carbon export and, importantly, controlling the efficiency of fertilisation.
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Meyer, Amelie, Kurt L. Polzin, Bernadette M. Sloyan, and Helen E. Phillips. "Internal Waves and Mixing near the Kerguelen Plateau." Journal of Physical Oceanography 46, no. 2 (February 2015): 417–37. http://dx.doi.org/10.1175/jpo-d-15-0055.1.
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AbstractIn the stratified ocean, turbulent mixing is primarily attributed to the breaking of internal waves. As such, internal waves provide a link between large-scale forcing and small-scale mixing. The internal wave field north of the Kerguelen Plateau is characterized using 914 high-resolution hydrographic profiles from novel Electromagnetic Autonomous Profiling Explorer (EM-APEX) floats. Altogether, 46 coherent features are identified in the EM-APEX velocity profiles and interpreted in terms of internal wave kinematics. The large number of internal waves analyzed provides a quantitative framework for characterizing spatial variations in the internal wave field and for resolving generation versus propagation dynamics. Internal waves observed near the Kerguelen Plateau have a mean vertical wavelength of 200 m, a mean horizontal wavelength of 15 km, a mean period of 16 h, and a mean horizontal group velocity of 3 cm s−1. The internal wave characteristics are dependent on regional dynamics, suggesting that different generation mechanisms of internal waves dominate in different dynamical zones. The wave fields in the Subantarctic/Subtropical Front and the Polar Front Zone are influenced by the local small-scale topography and flow strength. The eddy-wave field is influenced by the large-scale flow structure, while the internal wave field in the Subantarctic Zone is controlled by atmospheric forcing. More importantly, the local generation of internal waves not only drives large-scale dissipation in the frontal region but also downstream from the plateau. Some internal waves in the frontal region are advected away from the plateau, contributing to mixing and stratification budgets elsewhere.
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Duncan, R. A., P. G. Quilty, J. Barling, and J. M. Fox. "Geological development of Heard Island, Central Kerguelen Plateau." Australian Journal of Earth Sciences 63, no. 1 (January 2, 2016): 81–89. http://dx.doi.org/10.1080/08120099.2016.1139000.
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Srivastava, Rajesh K., Fei Wang, Wenbei Shi, Anup K. Sinha, and Kenneth L. Buchan. "Nature of Cretaceous dolerite dikes with two distinct trends in the Damodar Valley, eastern India: Constraints on their linkage to mantle plumes and large igneous provinces from 40Ar/39Ar geochronology and geochemistry." Lithosphere 12, no. 1 (December 12, 2019): 40–52. http://dx.doi.org/10.1130/l1108.1.
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Abstract Two distinct sets of Cretaceous dolerite dikes intrude the Chhotanagpur gneissic complex of eastern India, mostly within the Damodar Valley Gondwanan sedimentary basins. One dike set trends NNE to ENE, whereas the other set, which includes the prominent Salma dike, trends NW to NNW. One dike from each set in the Raniganj Basin was dated using the 40Ar/39Ar method in order to resolve a controversy concerning the emplacement age of the Salma dike. The NE-trending dike yielded a plateau age of 70.5 ± 0.9 Ma, whereas the NNW-trending Salma dike is much older, with a plateau age of 116.0 ± 1.4 Ma. These results demonstrate that the Salma dike was emplaced at ca. 116 Ma and not at ca. 65 Ma, as suggested in an earlier study. Geochemical characteristics of the two dikes are also distinct and indicate that they belong to previously identified high-Ti and low-Ti dolerite groups, respectively. The observed geochemical characteristics of both dike sets are comparable with the geochemistry of basalts of the Kerguelen Plateau, Bunbury Island, and Rajmahal Group I and suggest a connection to mantle plumes. The new age data presented herein indicate that these two magmatic episodes in the eastern Indian Shield were related to the ca. 120–100 Ma Kerguelen mantle plume and its associated Greater Kerguelen large igneous province and the ca. 70–65 Ma Réunion plume and its associated Deccan large igneous province, respectively.
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Maschette, Dale, Paul Burch, Bryn Farmer, Emma Woodcock, Clara Péron, Breanna Cramer, Caleb Gardner, and Dirk C. Welsford. "Population dynamics and spatial structure of the grey rockcod (Lepidonotothen squamifrons) in the vicinity of Heard Island and the McDonald Islands." PLOS ONE 19, no. 5 (May 14, 2024): e0298754. http://dx.doi.org/10.1371/journal.pone.0298754.
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The grey rockcod, Lepidonotothen squamifrons is an important prey species for seals, penguins and Patagonian toothfish (Dissostichus eleginoides) in the Southern Ocean. Across the Kerguelen Plateau, the species was fished to commercial extinction (ca. 152 000 tonnes between 1971 and 1978) prior to the declaration of the French Exclusive Economic Zone in 1979 and the Australian Fishing Zone in 1981. In this study we estimate; age, growth, maturity, sex ratio, body condition (weight-at-length), and population density of grey rockcod using data from 19 trawl surveys from 1990 to 2014. There appeared to be three distinct geographical populations, with differences in biological parameters within each population. This study has identified separate metapopulations within the southern region of the Kerguelen Plateau and we recommend that management should take into account the different characteristics of these populations, and that this meta-population structure may be a factor in why this species required several decades to show signs of recovery.
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van der Merwe, P., A. R. Bowie, F. Quéroué, L. Armand, S. Blain, F. Chever, D. Davies, et al. "Sourcing the iron in the naturally fertilised bloom around the Kerguelen Plateau: particulate trace metal dynamics." Biogeosciences 12, no. 3 (February 6, 2015): 739–55. http://dx.doi.org/10.5194/bg-12-739-2015.
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Abstract. The KEOPS2 project aims to elucidate the role of natural Fe fertilisation on biogeochemical cycles and ecosystem functioning, including quantifying the sources and processes by which iron is delivered in the vicinity of the Kerguelen Archipelago, Southern Ocean. The KEOPS2 process study used an upstream high-nutrient, low-chlorophyll (HNLC), deep water (2500 m), reference station to compare with a shallow (500 m), strongly fertilised plateau station and continued the observations to a downstream, bathymetrically trapped recirculation of the Polar Front where eddies commonly form and persist for hundreds of kilometres into the Southern Ocean. Over the Kerguelen Plateau, mean particulate (1–53 μm) Fe and Al concentrations (pFe = 13.4 nM, pAl = 25.2 nM) were more than 20-fold higher than at an offshore (lower-productivity) reference station (pFe = 0.53 nM, pAl = 0.83 nM). In comparison, over the plateau dissolved Fe levels were only elevated by a factor of ~ 2. Over the Kerguelen Plateau, ratios of pMn / pAl and pFe / pAl resemble basalt, likely originating from glacial/fluvial inputs into shallow coastal waters. In downstream, offshore deep-waters, higher pFe / pAl, and pMn / pAl ratios were observed, suggesting loss of lithogenic material accompanied by retention of pFe and pMn. Biological uptake of dissolved Fe and Mn and conversion into the biogenic particulate fraction or aggregation of particulate metals onto bioaggregates also increased these ratios further in surface waters as the bloom developed within the recirculation structure. While resuspension of shelf sediments is likely to be one of the important mechanisms of Fe fertilisation over the plateau, fluvial and glacial sources appear to be important to areas downstream of the island. Vertical profiles within an offshore recirculation feature associated with the Polar Front show pFe and pMn levels that were 6-fold and 3.5-fold lower, respectively, than over the plateau in surface waters, though still 3.6-fold and 1.7-fold higher respectively than the reference station. Within the recirculation feature, strong depletions of pFe and pMn were observed in the remnant winter water (temperature-minimum) layer near 175 m, with higher values above and below this depth. The correspondence between the pFe minima and the winter water temperature minima implies a seasonal cycle is involved in the supply of pFe into the fertilised region. This observed association is indicative of reduced supply in winter, which is counterintuitive if sediment resuspension and entrainment within the mixed layer is the primary fertilising mechanism to the downstream recirculation structure. Therefore, we hypothesise that lateral transport of pFe from shallow coastal waters is strong in spring, associated with snow melt and increased runoff due to rainfall, drawdown through summer and reduced supply in winter when snowfall and freezing conditions predominate in the Kerguelen region.
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van der Merwe, P., A. R. Bowie, F. Quéroué, L. Armand, S. Blain, F. Chever, D. Davies, et al. "Sourcing the iron in the naturally-fertilised bloom around the Kerguelen Plateau: particulate trace metal dynamics." Biogeosciences Discussions 11, no. 9 (September 18, 2014): 13389–432. http://dx.doi.org/10.5194/bgd-11-13389-2014.
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Abstract. The KEOPS2 project aims to elucidate the role of natural Fe fertilisation on biogeochemical cycles and ecosystem functioning, including quantifying the sources and processes by which iron is delivered in the vicinity of the Kerguelen Archipelago, Southern Ocean. The KEOPS2 process study used an upstream HNLC, deep water (2500 m), reference station to compare with a shallow (500 m), strongly fertilised plateau station and continued the observations to a downstream, bathymetrically trapped recirculation of the Polar Front where eddies commonly form and persist for hundreds of kilometres into the Southern Ocean. Over the Kerguelen Plateau, mean particulate (1–53 μm) Fe and Al concentrations (pFe = 13.4 nM, pAl = 25.2 nM) were more than 20-fold higher than at an offshore (lower-productivity) reference station (pFe = 0.53 nM, pAl = 0.83 nM). In comparison, over the plateau dissolved Fe levels were only elevated by a factor of ∼2. Over the Kerguelen Plateau, ratios of pMn/pAl and pFe/pAl resemble basalt, likely originating from glacial/fluvial inputs into shallow coastal waters. In downstream, offshore deep-waters, higher pFe/pAl, and pMn/pAl ratios were observed, suggesting loss of lithogenic material accompanied by retention of pFe and pMn. Biological uptake of dissolved Fe and Mn and conversion into the biogenic particulate fraction or aggregation of particulate metals onto bioaggregates also increased these ratios further in surface waters as the bloom developed within the recirculation structure. While resuspension of shelf sediments is likely to be one of the important mechanisms of Fe fertilisation over the plateau, fluvial and glacial sources appear to be important to areas downstream of the island. Vertical profiles within an offshore recirculation feature associated with the Polar Front show pFe and pMn levels that were 6-fold and 3.5-fold lower respectively than over the plateau in surface waters, though still 3.6-fold and 1.7-fold higher respectively than the reference station. Within the recirculation feature, strong depletions of pFe and pMn were observed in the remnant winter water (temperature-minimum) layer near 175 m, with higher values above and below this depth. The correspondence between the pFe minima and the winter water temperature minima implies a seasonal cycle is involved in the supply of pFe into the fertilized region. This observed association is indicative of reduced supply in winter, which is counterintuitive if sediment resuspension and entrainment within the mixed layer is the primary fertilising mechanism to the downstream recirculation structure. Therefore, we hypothesise that lateral transport of pFe from shallow coastal waters is strong in spring, associated with snow melt and increased runoff due to rainfall, drawdown through summer and reduced supply in winter when snowfall and freezing conditions predominate in the Kerguelen region.
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Tynan, Cynthia T. "Cetacean distributions and oceanographic features near the Kerguelen Plateau." Geophysical Research Letters 24, no. 22 (November 15, 1997): 2793–96. http://dx.doi.org/10.1029/97gl02860.
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Tikku, Anahita A., and Steven C. Cande. "On the fit of Broken Ridge and Kerguelen plateau." Earth and Planetary Science Letters 180, no. 1-2 (July 2000): 117–32. http://dx.doi.org/10.1016/s0012-821x(00)00157-6.
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Park, Young-Hyang, Jean-Luc Fuda, Isabelle Durand, and Alberto C. Naveira Garabato. "Internal tides and vertical mixing over the Kerguelen Plateau." Deep Sea Research Part II: Topical Studies in Oceanography 55, no. 5-7 (March 2008): 582–93. http://dx.doi.org/10.1016/j.dsr2.2007.12.027.
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Leclaire, Lucien, Yannis Bassias, Micheline Denis-Clocchiatti, Hugh Davies, Isabelle Gautier, Bernard Gensous, Pierre-Jean Giannesini, et al. "Lower cretaceous basalt and sediments from the Kerguelen Plateau." Geo-Marine Letters 7, no. 4 (December 1987): 169–76. http://dx.doi.org/10.1007/bf02242768.
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Chever, F., G. Sarthou, E. Bucciarelli, S. Blain, and A. R. Bowie. "An iron budget during the natural iron fertilisation experiment KEOPS (Kerguelen Islands, Southern Ocean)." Biogeosciences Discussions 6, no. 4 (July 10, 2009): 6803–37. http://dx.doi.org/10.5194/bgd-6-6803-2009.
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Abstract. Total dissolvable iron (TDFe) was measured in the water column above and in the surrounding of the Kerguelen Plateau (Indian sector of the Southern Ocean) during the KErguelen Ocean Plateau compared Study (KEOPS) cruise. TDFe concentrations ranged from 0.90 to 65.6 nmol L−1 above the plateau and from 0.34 to 2.23 nmol L−1 offshore of the plateau. Station C1 located south of the plateau, near Heard Island, exhibited very high values (329–770 nmol L−1). Apparent particulate iron (Feapp), calculated as the difference between the TDFe and the dissolved iron measured on board (DFe) represented 95±5% of the TDFe above the plateau, suggesting that particles and refractory colloids largely dominated the iron pool. This paper presents a budget of DFe and Feapp above the plateau. Lateral advection of water that had been in contact with the continental shelf of Heard Island seems to be the predominant source of Feapp and DFe above the plateau, with a supply of 9.7±2.3×106 and 8.3±6.7×103 mol d−1, respectively. The residence times of 1.7 and 48 days estimated for Feapp and DFe, respectively, indicate a rapid turnover in the surface water. A comparison between Feapp and total particulate iron (TPFe) suggests that the total dissolved fraction is mainly constituted of small refractory colloids. This fraction does not seem to be a potential source of iron to the phytoplankton in our study. Finally, when taking into account the lateral supply of dissolved iron, the seasonal carbon sequestration efficiency was estimated at 154 000 mol C (mol Fe)−1, which is 4-fold lower than the previously estimated value in this area but still 18-fold higher than the one estimated during the other study of a natural iron fertilisation experiment, CROZEX.
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Chever, F., G. Sarthou, E. Bucciarelli, S. Blain, and A. R. Bowie. "An iron budget during the natural iron fertilisation experiment KEOPS (Kerguelen Islands, Southern Ocean)." Biogeosciences 7, no. 2 (February 2, 2010): 455–68. http://dx.doi.org/10.5194/bg-7-455-2010.
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Abstract. Total dissolvable iron (TDFe) was measured in the water column above and in the surrounding of the Kerguelen Plateau (Indian sector of the Southern Ocean) during the KErguelen Ocean Plateau compared Study (KEOPS) cruise. TDFe concentrations ranged from 0.90 to 65.6 nmol L−1 above the plateau and from 0.34 to 2.23 nmol L−1 offshore of the plateau. Station C1 located south of the plateau, near Heard Island, exhibited very high values (329–770 nmol L−1). Apparent particulate iron (Feapp), calculated as the difference between the TDFe and the dissolved iron measured on board (DFe) represented 95±5% of the TDFe above the plateau, suggesting that particles and refractory colloids largely dominated the iron pool. This paper presents a budget of DFe and Feapp above the plateau. Lateral advection of water that had been in contact with the continental shelf of Heard Island seems to be the predominant source of Feapp and DFe above the plateau, with a supply of 9.7±3.6×106 and 8.3±11.6×103 mol d−1, respectively. The residence times of 1.7 and 48 days estimated for Feapp and DFe respectively, indicate a rapid turnover in the surface water. A comparison between Feapp and total particulate iron (TPFe) suggests that the total dissolved fraction is mainly constituted of small refractory colloids. This fraction does not seem to be a potential source of iron to the phytoplankton in our study. Finally, when taking into account the lateral supply of dissolved iron, the seasonal carbon sequestration efficiency was estimated at 154 000 mol C (mol Fe)−1, which is 4-fold lower than the previously estimated value in this area but still 18-fold higher than the one estimated during the other study of a natural iron fertilisation experiment, CROZEX.
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Ayress, Michael A., Patrick De Deckker, and Graham P. Coles. "A taxonomic and distributional survey of marine benthonic Ostracoda off Kerguelen and Heard Islands, South Indian Ocean." Journal of Micropalaeontology 23, no. 1 (May 1, 2004): 15–38. http://dx.doi.org/10.1144/jm.23.1.15.
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Abstract. From an examination of 34 grab and dredge samples ranging from 110 m to 3584 m water depth, collected during Eltanin cruise 47 across the Kerguelen Plateau, 26 shallow-water and 35 deep-sea benthonic ostracod species have been identified. Systematic notes and illustrations of the common and some of the rare species are presented. Two new species are described: Philoneptunus cassidyi n. sp. and Taracythere abyssora n. sp. Comparisons made with the Atlantic and SW Pacific Oceans and circum-Antarctic regions indicate that the fauna comprises dominantly cosmopolitan deep-sea species while most of the other species have close affinities with the SW Pacific. In the Kerguelen material, seven distinct depth assemblages appear to correspond well with differing watermasses and there is evidence that the relatively shallow position of Antarctic Intermediate Water permits elevation of the upper depth limits of some deep-sea species. Some species have developed ornament of fine reticulation, features not previously seen in those species outside the Kerguelen region.
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Planchon, F., D. Ballas, A. J. Cavagna, A. R. Bowie, D. Davies, T. Trull, E. Laurenceau, P. Van Der Merwe, and F. Dehairs. "Carbon export in the naturally iron-fertilized Kerguelen area of the Southern Ocean based on the <sup>234</sup>Th approach." Biogeosciences Discussions 11, no. 11 (November 25, 2014): 15991–6032. http://dx.doi.org/10.5194/bgd-11-15991-2014.
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Abstract. The Kerguelen Plateau region in the Indian sector of the Southern Ocean supports annually a large-scale phytoplankton bloom which is naturally fertilized with iron. As part of the second KErguelen Ocean and Plateau compared Study expedition (KEOPS2) in austral spring (October–November 2011), we examined upper-ocean Particulate Organic Carbon (POC) export using the 234Th approach. We aimed at characterizing the spatial and the temporal variability of POC export production at high productivity sites over and downstream the Kerguelen plateau. Export production is compared to a High Nutrient Low Chlorophyll area upstream of the plateau in order to assess the impact of iron-induced productivity on the vertical export of carbon. Deficits in 234Th activities relative to its parent nuclide 238U were observed at all stations in surface waters, indicating that scavenging by particles occurred during the early stages of the phytoplankton bloom. 234Th export was lowest at reference station R-2 (412 ± 134 dpm m–2 d–1) and highest inside a~permanent meander of the Polar Front (PF) at stations E (1995 ± 176 dpm m–2 d–1, second visit E-3) where a detailed time series was obtained as part of a~pseudo-lagrangian study. 234Th export over the central plateau was relatively limited at station A3 early (776 ± 171 dpm m–2 d–1, first visit A3-1) and late in the survey (993 ± 223 dpm m–2 d–1, second visit A3-2), but it was higher at high biomass stations TNS-8 (1372 ± 255 dpm m–2 d–1) and E-4W (1068 ± 208 dpm m–2 d–1) in waters which could be considered as derived from plateau. Limited 234Th export of 973 ± 207 dpm m–2 d–1 was also found in the northern branch of the Kerguelen bloom located downstream of the island, north of the PF (station F-L). The 234Th results support that Fe fertilization increased particle export in all iron fertilized waters. The impact was greatest in the recirculation feature (3–4 fold at 200 m depth), but more moderate over the central Kerguelen plateau and in the northern plume of the Kerguelen bloom (∼2-fold at 200 m depth). The C : Th ratio of large (> 53 μm) potentially sinking particles collected via sequential filtration using in situ pumping (ISP) systems were used to convert the 234Th flux into a POC export flux. The C : Th ratios of sinking particles were highly variable (range: 3.1 ± 0.1–10.5 ± 0.2 μmol dpm–1) with no clear site related trend, despite the variety of ecosystem responses in the fertilized regions. C : Th ratios showed a decreasing trend between 100 and 200 m depth suggesting preferential loss of carbon relative to 234Th possibly due to heterotrophic degradation and/or grazing activity. Comparison of the C : Th ratios within sinking particles obtained with the drifting sediment traps showed in most cases very good agreement to those collected via ISP deployments (> 53 μm particles). Carbon export production varied between 3.5 ± 0.9 mmol m–2 d–1 and 11.8 ± 1.3 mmol m–2 d–1 from the upper 100 m and between 1.8 ± 0.9 mmol m–2 d–1 and 8.2 ± 0.9 mmol m–2 d–1 from the upper 200 m. Highest export production was found inside the PF meander with a range of 5.4 ± 0.7 mmol m–2 d–1 to 11.8 ± 1.1 mmol m–2 d–1 at 100 m depth decreasing to 5.3 ± 1.0 mmol m–2 d–1 to 8.2 ± 0.8 mmol m–2 d–1 at 200 m depth over the 19 day survey period. The impact of Fe fertilization is highest inside the PF meander with 2.9- up to 4.5-fold higher carbon flux at 200 m depth in comparison to the HNLC control station. The impact of Fe fertilization was significantly less over the central plateau (stations A3 and E-4W) and in the northern branch of the bloom (station F-L) with 1.6- up to 2.0-fold higher carbon flux compared to the reference station R. Export efficiencies (ratio of export to primary production) were particularly variable with relatively high values in the recirculation feature (6–27%) and low values (1–5%) over the central plateau (station A3) and north of the PF (station F-L) indicating spring biomass accumulation. Comparison with KEOPS1 results indicated that carbon export production is much lower during the onset of the bloom in austral spring in comparison to the peak and declining phase in late summer.
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Dehairs, F., F. Fripiat, A. J. Cavagna, T. W. Trull, C. Fernandez, D. Davies, A. Roukaerts, D. Fonseca Batista, F. Planchon, and M. Elskens. "Nitrogen cycling in the Southern Ocean Kerguelen Plateau area: evidence for significant surface nitrification from nitrate isotopic compositions." Biogeosciences 12, no. 5 (March 5, 2015): 1459–82. http://dx.doi.org/10.5194/bg-12-1459-2015.
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Abstract. This paper presents whole water column data for nitrate N, O isotopic composition for the Kerguelen Plateau area and the basin extending east of Heard Island, aiming at understanding the N-cycling in this naturally iron fertilized area that is characterized by large re-current phytoplankton blooms. The KEOPS 2 expedition (October–November 2011) took place in spring season and complements knowledge gathered during an earlier summer expedition to the same area (KEOPS 1, February–March 2005). As noted by others a remarkable condition of the system is the moderate consumption of nitrate over the season (nitrate remains >20 μM) while silicic acid becomes depleted, suggesting significant recycling of nitrogen. Nitrate isotopic signatures in the upper water column do mimic this condition, with surprising overlap of spring and summer regressions of δ18ONO3 vs. δ15NNO3 isotopic compositions. These regressions obey rather closely the 18&varepsilon;/15&varepsilon; discrimination expected for nitrate uptake (18&varepsilon;/15&varepsilon; = 1), but regression slopes as large as 1.6 were observed for the mixed layer above the Kerguelen Plateau. A preliminarily mass balance calculation for the early bloom period points toward significant nitrification occurring in the mixed layer and which may be equivalent to up to 47% of nitrate uptake above the Kerguelen Plateau. A further finding concerns deep ocean low δ18ONO3 values (<2‰) underlying high chlorophyll waters at the Polar Front Zone and which cannot be explained by remineralization and nitrification of the local particulate nitrogen flux, which is too small in magnitude. However, the studied area is characterized by a complex recirculation pattern that would keep deep waters in the area and could impose a seasonally integrated signature of surface water processes on the deep waters.
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Dehairs, F., F. Fripiat, A. J. Cavagna, T. W. Trull, C. Fernandez, D. Davies, A. Roukaerts, D. Fonseca Batista, F. Planchon, and M. Elskens. "Nitrogen cycling in the Southern Ocean Kerguelen Plateau area: evidence for significant surface nitrification from nitrate isotopic compositions." Biogeosciences Discussions 11, no. 9 (September 26, 2014): 13905–55. http://dx.doi.org/10.5194/bgd-11-13905-2014.
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Abstract. This paper presents whole water column data for nitrate N, O isotopic composition for the Kerguelen Plateau area and the basin extending east of the island, aiming at understanding the N-cycling in this naturally iron fertilized area that is characterized by large re-current phytoplankton blooms. The KEOPS 2 expedition (October–November 2011) took place in spring season and complements knowledge gathered during an earlier summer expedition to the same area (KEOPS 1, February–March 2005). As noted by others a remarkable condition of the system is the moderate consumption of nitrate over the season (nitrate remains > 20 μM) while silicic acid becomes depleted, suggesting significant recycling of nitrogen. Nitrate isotopic signatures in the upper water column do mimic this condition, with surprising overlap of spring and summer regressions of δ18ONO3 vs. δ15NNO3 isotopic compositions. These regressions obey rather closely the 18&varepsilon;/15&varepsilon; discrimination expected for nitrate uptake (18&varepsilon;/15&varepsilon; = 1), but regression slopes as large as 1.6 were observed for the mixed layer above the Kerguelen Plateau. A preliminary mass balance calculation for the early bloom period points toward significant nitrification occurring in the mixed layer and which could account for up to 80 % of nitrate uptake above the Kerguelen Plateau. A further finding concerns deep ocean low δ18ONO3 values (< 2‰) underlying high chlorophyll waters at the Polar Front Zone and which cannot be explained by remineralisation and nitrification of the local particulate nitrogen flux, which is too small in magnitude. However, the studied area is characterised by a complex recirculation pattern that would keep deep waters in the area and could impose a seasonally integrated signature of surface water processes on the deep waters.
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Planchon, F., D. Ballas, A. J. Cavagna, A. R. Bowie, D. Davies, T. Trull, E. C. Laurenceau-Cornec, P. Van Der Merwe, and F. Dehairs. "Carbon export in the naturally iron-fertilized Kerguelen area of the Southern Ocean based on the <sup>234</sup>Th approach." Biogeosciences 12, no. 12 (June 23, 2015): 3831–48. http://dx.doi.org/10.5194/bg-12-3831-2015.
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Abstract. This study examined upper-ocean particulate organic carbon (POC) export using the 234Th approach as part of the second KErguelen Ocean and Plateau compared Study expedition (KEOPS2). Our aim was to characterize the spatial and the temporal variability of POC export during austral spring (October–November 2011) in the Fe-fertilized area of the Kerguelen Plateau region. POC export fluxes were estimated at high productivity sites over and downstream of the plateau and compared to a high-nutrient low-chlorophyll (HNLC) area upstream of the plateau in order to assess the impact of iron-induced productivity on the vertical export of carbon. Deficits in 234Th activities were observed at all stations in surface waters, indicating early scavenging by particles in austral spring. 234Th export was lowest at the reference station R-2 and highest in the recirculation region (E stations) where a pseudo-Lagrangian survey was conducted. In comparison 234Th export over the central plateau and north of the polar front (PF) was relatively limited throughout the survey. However, the 234Th results support that Fe fertilization increased particle export in all iron-fertilized waters. The impact was greatest in the recirculation feature (3–4 fold at 200 m depth, relative to the reference station), but more moderate over the central Kerguelen Plateau and in the northern plume of the Kerguelen bloom (~2-fold at 200 m depth). The C : Th ratio of large (>53 μm) potentially sinking particles collected via sequential filtration using in situ pumping (ISP) systems was used to convert the 234Th flux into a POC export flux. The C : Th ratios of sinking particles were highly variable (3.1 ± 0.1 to 10.5 ± 0.2 μmol dpm−1) with no clear site-related trend, despite the variety of ecosystem responses in the fertilized regions. C : Th ratios showed a decreasing trend between 100 and 200 m depth suggesting preferential carbon loss relative to 234Th possibly due to heterotrophic degradation and/or grazing activity. C : Th ratios of sinking particles sampled with drifting sediment traps in most cases showed very good agreement with ratios for particles collected via ISP deployments (>53 μm particles). Carbon export production varied between 3.5 ± 0.9 and 11.8 ± 1.3 mmol m−2 d−1 from the upper 100 m and between 1.8 ± 0.9 and 8.2 ± 0.9 mmol m−2 d−1 from the upper 200 m. The highest export production was found inside the PF meander with a range of 5.3 ± 1.0 to 11.8 ± 1.1 mmol m−2 d−1 over the 19-day survey period. The impact of Fe fertilization is highest inside the PF meander with 2.9–4.5-fold higher carbon flux at 200 m depth in comparison to the HNLC control station. The impact of Fe fertilization was significantly less over the central plateau (stations A3 and E-4W) and in the northern branch of the bloom (station F-L) with 1.6–2.0-fold higher carbon flux compared to the reference station R. Export efficiencies (ratio of export to primary production and ratio of export to new production) were particularly variable with relatively high values in the recirculation feature (6 to 27 %, respectively) and low values (1 to 5 %, respectively) over the central plateau (station A3) and north of the PF (station F-L), indicating spring biomass accumulation. Comparison with KEOPS1 results indicated that carbon export production is much lower during the onset of the bloom in austral spring than during the peak and declining phases in late summer.
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Bowie, A. R., P. van der Merwe, F. Quéroué, T. Trull, M. Fourquez, F. Planchon, G. Sarthou, et al. "Iron budgets for three distinct biogeochemical sites around the Kerguelen archipelago (Southern Ocean) during the natural fertilisation experiment KEOPS-2." Biogeosciences Discussions 11, no. 12 (December 19, 2014): 17861–923. http://dx.doi.org/10.5194/bgd-11-17861-2014.
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Abstract. Iron availability in the Southern Ocean controls phytoplankton growth, community composition and the uptake of atmospheric CO2 by the biological pump. The KEOPS-2 experiment took place around the Kerguelen plateau in the Indian sector of the Southern Ocean, a region naturally fertilised with iron at the scale of hundreds to thousands of square kilometres, producing a mosaic of spring blooms which showed distinct biological and biogeochemical responses to fertilisation. This paper presents biogeochemical iron budgets (incorporating vertical and lateral supply, internal cycling, and sinks) for three contrasting sites: an upstream high-nutrient low-chlorophyll reference, over the plateau, and in the offshore plume east of Kerguelen Island. These budgets show that distinct regional environments driven by complex circulation and transport pathways are responsible for differences in the mode and strength of iron supply, with vertical supply dominant on the plateau and lateral supply dominant in the plume. Iron supply from "new" sources to surface waters of the plume was double that above the plateau and 20 times greater than at the reference site, whilst iron demand (measured by cellular uptake) in the plume was similar to the plateau but 40 times greater than the reference. "Recycled" iron supply by bacterial regeneration and zooplankton grazing was a relative minor component at all sites (<8% of "new" supply), in contrast to earlier findings from other biogeochemical iron budgets in the Southern Ocean. Over the plateau, a particulate iron dissolution term of 2.5% was invoked to balance the budget; this approximately doubled the standing stock of dissolved iron in the mixed layer. The exchange of iron between dissolved, biogenic and lithogenic particulate pools was highly dynamic in time and space, resulting in a decoupling of iron supply and carbon export and, importantly, controlling the efficiency of fertilisation.
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Williams, R., A. J. Smolenski, and R. W. G. White. "Mitochondrial DNA variation of Champsocephalus gunnari Lönnberg (Pisces: Channichthyidae) stocks on the Kerguelen Plateau, southern Indian Ocean." Antarctic Science 6, no. 3 (September 1994): 347–52. http://dx.doi.org/10.1017/s0954102094000520.
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The distribution of the icefish Champsocephalus gunnari on the Kerguelen Plateau is confined to the inner shelves of Heard and Kerguelen islands and outlying banks where the water depth is less than 350 m. For fisheries management purposes, it is necessary to know whether fish from the various shelves and banks belong to one single or several separate populations. Analysis of the mitochondrial DNA of fish from various localities using restriction endonclease enzymes revealed no significant genetic heterogeneity between any of the localities. This does not preclude the existence of isolated stocks at the present time but indicates that the populations have been separated too recently for genetic isolation to be manifested, or that low-level interchange of fish between the populations may be maintaining genetic homogeneity.
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O’Toole, M., MA Hindell, JB Charrassin, and C. Guinet. "Foraging behaviour of southern elephant seals over the Kerguelen Plateau." Marine Ecology Progress Series 502 (April 15, 2014): 281–94. http://dx.doi.org/10.3354/meps10709.
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Duncan, R. A., T. J. Falloon, P. G. Quilty, and M. F. Coffin. "Widespread Neogene volcanism on Central Kerguelen Plateau, Southern Indian Ocean." Australian Journal of Earth Sciences 63, no. 4 (May 18, 2016): 379–92. http://dx.doi.org/10.1080/08120099.2016.1221857.
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Bénard, Francine, Jean-Paul Callot, Roland Vially, Julien Schmitz, Walter Roest, Martin Patriat, and Benoît Loubrieu. "The Kerguelen plateau: Records from a long-living/composite microcontinent." Marine and Petroleum Geology 27, no. 3 (March 2010): 633–49. http://dx.doi.org/10.1016/j.marpetgeo.2009.08.011.
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Fröhlich, François, and Emmanuelle Wicquart. "Upper cretaceous and paleogene sediments from the Northern Kerguelen Plateau." Geo-Marine Letters 9, no. 3 (September 1989): 127–33. http://dx.doi.org/10.1007/bf02431039.
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Park, Young-Hyang, Fabien Roquet, Isabelle Durand, and Jean-Luc Fuda. "Large-scale circulation over and around the Northern Kerguelen Plateau." Deep Sea Research Part II: Topical Studies in Oceanography 55, no. 5-7 (March 2008): 566–81. http://dx.doi.org/10.1016/j.dsr2.2007.12.030.
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Armand, Leanne K., X. Crosta, B. Quéguiner, J. Mosseri, and N. Garcia. "Diatoms preserved in surface sediments of the northeastern Kerguelen Plateau." Deep Sea Research Part II: Topical Studies in Oceanography 55, no. 5-7 (March 2008): 677–92. http://dx.doi.org/10.1016/j.dsr2.2007.12.032.
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Weldrick, Christine K., Rowan Trebilco, Diana M. Davies, and Kerrie M. Swadling. "Trophodynamics of Southern Ocean pteropods on the southern Kerguelen Plateau." Ecology and Evolution 9, no. 14 (June 20, 2019): 8119–32. http://dx.doi.org/10.1002/ece3.5380.
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Park, Y. H., J. H. Lee, I. Durand, and C. S. Hong. "Validation of Thorpe-scale-derived vertical diffusivities against microstructure measurements in the Kerguelen region." Biogeosciences 11, no. 23 (December 11, 2014): 6927–37. http://dx.doi.org/10.5194/bg-11-6927-2014.
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Abstract. The Thorpe scale is an energy-containing vertical overturning scale of large eddies associated with shear-generated turbulence. This study investigates indirect estimates of vertical diffusivities from the Thorpe scale method in the polar front region east of the Kerguelen Islands based on fine-scale density profiles gathered during the 2011 KEOPS2 (KErguelen Ocean and Plateau compared Study 2) cruise. These diffusivities are validated in comparison with diffusivities estimated from the turbulence dissipation rate directly measured via a TurboMAP (Turbulence ocean Microstructure Acquisition Profiler) microstructure profiler. The results are sensitive to the choice of the diffusivity parameterization and the overturn ratio Ro, and the optimal results have been obtained from the parameterization by Shih et al. (2005) and the Ro = 0.25 criterion, rather than the parameterization by Osborn (1980) and the Ro = 0.2 criterion originally suggested by Gargett and Garner (2008). The Thorpe-scale-derived diffusivities in the KEOPS2 region show a high degree of spatial variability, ranging from a canonical value of O(10−5) m2 s−1 in the Winter Water layer and in the area immediately north of the polar front to a high value of O(10−4) m2 s−1 in the seasonal thermocline between the surface mixed layer and the Winter Water. The latter high diffusivities are found especially over the shallow plateau southeast of the Kerguelen Islands and along the polar front that is attached to the escarpment northeast of the islands. The interaction of strong frontal flow with prominent bottom topography likely causes the observed elevated mixing rates.
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Meyer, Amelie, Bernadette M. Sloyan, Kurt L. Polzin, Helen E. Phillips, and Nathaniel L. Bindoff. "Mixing Variability in the Southern Ocean." Journal of Physical Oceanography 45, no. 4 (April 2015): 966–87. http://dx.doi.org/10.1175/jpo-d-14-0110.1.
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AbstractA key remaining challenge in oceanography is the understanding and parameterization of small-scale mixing. Evidence suggests that topographic features play a significant role in enhancing mixing in the Southern Ocean. This study uses 914 high-resolution hydrographic profiles from novel EM-APEX profiling floats to investigate turbulent mixing north of the Kerguelen Plateau, a major topographic feature in the Southern Ocean. A shear–strain finescale parameterization is applied to estimate diapycnal diffusivity in the upper 1600 m of the ocean. The indirect estimates of mixing match direct microstructure profiler observations made simultaneously. It is found that mixing intensities have strong spatial and temporal variability, ranging from O(10−6) to O(10−3) m2 s−1. This study identifies topographic roughness, current speed, and wind speed as the main factors controlling mixing intensity. Additionally, the authors find strong regional variability in mixing dynamics and enhanced mixing in the Antarctic Circumpolar Current frontal region. This enhanced mixing is attributed to dissipating internal waves generated by the interaction of the Antarctic Circumpolar Current and the topography of the Kerguelen Plateau. Extending the mixing observations from the Kerguelen region to the entire Southern Ocean, this study infers a large water mass transformation rate of 17 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) across the boundary of Antarctic Intermediate Water and Upper Circumpolar Deep Water in the Antarctic Circumpolar Current. This work suggests that the contribution of mixing to the Southern Ocean overturning circulation budget is particularly significant in fronts.