| 1. |
- Gülk, Birte, 1994, et al.
(författare)
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Variability and Remote Controls of the Warm-Water Halo and Taylor Cap at Maud Rise
- 2023
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Ingår i: Journal of Geophysical Research: Oceans. - 2169-9275 .- 2169-9291. ; 128:7
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Tidskriftsartikel (refereegranskat)abstract
- The region of Maud Rise, a seamount in the Weddell Sea, is known for the occurrence of irregular polynya openings during the winter months. Hydrographic observations have shown the presence of a warmer water mass below the mixed layer along the seamount's flanks, commonly termed the warm-water Halo, surrounding a colder region above the rise, the Taylor Cap. Here we use two observational data sets, an eddy-permitting reanalysis product and regional high-resolution simulations, to investigate the interannual variability of the Halo and Taylor Cap for the period 2007–2022. Observations include novel hydrographic profiles obtained in the Maud Rise area in January 2022, during the first SO-CHIC cruise. It is demonstrated that the temperature of deep waters around Maud Rise exhibits strong interannual variability within the Halo and Taylor Cap, occasionally to such an extent that the two features become indistinguishable. A warming of deep waters by as much as 0.8°C is observed in the Taylor Cap during the years preceding the opening of a polynya in 2016 and 2017, starting in 2011. By analyzing regional simulations, we show that most of the observed variability in the Halo is forced remotely by advection of deep waters from the Weddell Gyre into the region surrounding Maud Rise. Our highest-resolution simulation indicates that mesoscale eddies subsequently transfer the properties of the Halo's deep waters onto the Taylor Cap. The eddies responsible for such transfer originate in an abrupt retroflection along the inner flank of the Halo.
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| 2. |
- Narayanan, Aditya, 1988, et al.
(författare)
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Zonal Distribution of Circumpolar Deep Water Transformation Rates and Its Relation to Heat Content on Antarctic Shelves
- 2023
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Ingår i: Journal of Geophysical Research-Oceans. - 2169-9275. ; 128:6
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Tidskriftsartikel (refereegranskat)abstract
- We analyze 15-year of observational data and a 5-year Southern Ocean model simulation to quantify the transformation rates of Circumpolar Deep Water (CDW) and the associated heat loss to the surface. This study finds that over the continental shelves of East Antarctica and the Weddell and Ross Seas, surface buoyancy fluxes transform similar to 4.4 Sv of surface waters into CDW, providing a path for CDW to lose heat to the surface. In addition, similar to 6.6 Sv of CDW are mixed with surface waters in the Weddell and Ross subpolar gyres. In contrast, enhanced stratification inhibits the outcropping of CDW isopycnals, reducing their transformation rates by a factor of similar to 8 over the continental shelf and by a factor of similar to 3 over the deeper ocean in the Amundsen and Bellingshausen Seas. The CDW retains its offshore warm properties as it intrudes over the continental shelves, resulting in elevated bottom temperatures there. This analysis demonstrates the importance of processes in subpolar gyres to erode CDW and to facilitate further transformation on the continental shelves, significantly reducing the heat able to access ice shelf fronts. This sheltering effect is strongest in the western Weddell Sea and tends to diminish toward the east, which helps explain the large zonal differences in continental-shelf bottom temperatures and the melt rates of Antarctic ice shelves. Plain Language Summary The continental slope around Antarctica acts as a barrier to deep and warmer offshore waters that can bring heat to the glaciers along the coastline, enhancing their melt rate and contributing to global sea level rise. Around the Antarctic continent these offshore waters, the so-called Circumpolar Deep Waters, differ in their ability to cross this barrier while retaining their heat, explaining to a large extent why West Antarctic glaciers melt much faster than other Antarctic ice sheets. We study the properties of the warm waters over the continental shelf and offshore regions and contrast them across regions. We show that in East Antarctica, the Ross Sea, and the Weddell Sea, deep warm waters are brought to the surface where they lose heat and mix with surface waters. However, in the Amundsen and Bellingshausen Seas, the warm water is insulated from the surface by land run-off of fresher and lighter waters that occupy the surface. These results highlight the importance of the subpolar gyres in sheltering Antarctic glaciers.
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| 3. |
- Sallee, J. B., et al.
(författare)
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Southern ocean carbon and heat impact on climate
- 2023
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Ingår i: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. - 1364-503X .- 1471-2962. ; 381:2249
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Tidskriftsartikel (refereegranskat)abstract
- The Southern Ocean greatly contributes to the regulation of the global climate by controlling important heat and carbon exchanges between the atmosphere and the ocean. Rates of climate change on decadal timescales are therefore impacted by oceanic processes taking place in the Southern Ocean, yet too little is known about these processes. Limitations come both from the lack of observations in this extreme environment and its inherent sensitivity to intermittent processes at scales that are not well captured in current Earth system models. The Southern Ocean Carbon and Heat Impact on Climate programme was launched to address this knowledge gap, with the overall objective to understand and quantify variability of heat and carbon budgets in the Southern Ocean through an investigation of the key physical processes controlling exchanges between the atmosphere, ocean and sea ice using a combination of observational and modelling approaches. Here, we provide a brief overview of the programme, as well as a summary of some of the scientific progress achieved during its first half. Advances range from new evidence of the importance of specific processes in Southern Ocean ventilation rate (e.g. storm-induced turbulence, sea-ice meltwater fronts, wind-induced gyre circulation, dense shelf water formation and abyssal mixing) to refined descriptions of the physical changes currently ongoing in the Southern Ocean and of their link with global climate.This article is part of a discussion meeting issue 'Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities'.
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