The southern ocean meridional overturning in the sea-ice sector is driven by freshwater fluxes

Pellichero, Violaine; Sallée, Jean‐Baptiste; Chapman, Christopher; Downes, Stephanie M.

doi:10.1038/s41467-018-04101-2

Cited by 90 publications

(131 citation statements)

References 48 publications

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“…Once in the surface layer, the upwelled UCDW is exposed to surface fluxes and can participate in the general wind-driven transport of water toward the Polar Front. This diapycnal upwelling occurs at a rate of about 2×10 −12 Sv/m 2 (assuming that the surface mixed layer deepens by 25 m over 150 days); this rate agrees well with an estimate of the transformation rate for the Ross Gyre region by Pellichero et al (2018).…”

Section: Discussionsupporting

confidence: 81%

The Regulation of Sea Ice Thickness by Double‐Diffusive Processes in the Ross Gyre

Bebieva

Speer

2019

JGR Oceans

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New fine‐scale observations from the central Ross Gyre reveal the presence of double‐diffusive staircase structures underlying the surface mixed layer. These structures are persistent over seasons, with more developed mixed layers within the double‐diffusive staircase in winter months. The sensitivity of the ice formation rate with respect to mixing processes within the main pycnocline (double‐diffusive versus purely turbulent mixing) is investigated with the 1‐D model. A scenario with purely turbulent mixing results in significant underestimates of sea ice thickness. However, a scenario when double‐diffusive mixing operates in the presence of weak shear yields plausible ranges for sea ice thickness that agrees well with the observations. The model results and observations suggest a peculiar feedback mechanism that promotes the self‐maintenance of double‐diffusive staircases. Suppression of the vertical heat fluxes due to the presence of a double‐diffusive staircase, compared to purely turbulent case, allows Upper Circumpolar Deep Water to be more exposed to surface buoyancy fluxes. Our results shed light on the process—double diffusion—that might account for estimated rates of winter water mass transformation in the central Ross Gyre.

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Section: Discussionsupporting

confidence: 81%

The Regulation of Sea Ice Thickness by Double‐Diffusive Processes in the Ross Gyre

Bebieva

Speer

2019

JGR Oceans

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“…WMT rates resulting from applying a globally constant freshwater flux of 5 times the difference between their imbalance 5 × 10 −9 m/s result is very small WMT rates (Figure 2a, Wijffels, 2001). We note that both OA and CORE freshwater fluxes have no or limited implementation of the effects of seasonal ice melt and refreezing on WMT, which may be significant for both products at higher densities ( n > 27 kg/m 3 ; Pellichero et al, 2018). In conclusion, to obtain physical realistic amount of WMT, an (almost) balanced air-sea flux product is required, which is why we continue this study using CORE.…”

Section: Choosing Air-sea Flux Product For Wmt Analysismentioning

confidence: 95%

The Effect of Air‐Sea Flux Products, Shortwave Radiation Depth Penetration, and Albedo on the Upper Ocean Overturning Circulation

Groeskamp

Iudicone

2018

Geophysical Research Letters

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Water mass transformation quantifies transport of matter between different density classes of the World Ocean. We present the first observationally based quantification of transformation rates due to air‐sea buoyancy fluxes, which considers different parameterizations of shortwave radiation depth penetration, including the influence of albedo and the Chlorophyll a concentration. The results provide a range of solutions that can be used to compare model‐based transformation rates against. We compared two air‐sea flux products with limited representation of ice dynamics at high latitudes. We find that variations in the air‐sea heat fluxes due to Chlorophyll a and its horizontal distribution are as important for water mass transformation rates than differences between the freshwater flux products. An accurate representation of the effects and spatial distribution of Chlorophyll a is required to obtain realistic transformation rates.

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“…The net buoyancy flux is dominated by the freshwater component. Data shown in panels (d)–(f) are taken from and described by Pellichero et al (). The bars over the top panels show the ASC classifications as in Figures and .…”

Section: Structure and Regional Variations Of The Ascmentioning

confidence: 99%

“…The influence of surface buoyancy fluxes on the structure of the ASF is less clear. Averaged over the Antarctic margins, freshwater fluxes have a larger impact on water transformation than heat fluxes (Abernathey et al, ; Pellichero et al, ; Figures 5d–5f). Dense water formed over the continental shelf, and eventually exported as AABW, is largely related to sea ice formation and the associated brine rejection in coastal polynyas (Tamura et al, ), located shoreward of the ASC (Figure e).…”

Section: Structure and Regional Variations Of The Ascmentioning

confidence: 99%

The Antarctic Slope Current in a Changing Climate

Thompson

Stewart

Spence

et al. 2018

Reviews of Geophysics

222

328

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The Antarctic Slope Current (ASC) is a coherent circulation feature that rings the Antarctic continental shelf and regulates the flow of water toward the Antarctic coastline. The structure and variability of the ASC influences key processes near the Antarctic coastline that have global implications, such as the melting of Antarctic ice shelves and water mass formation that determines the strength of the global overturning circulation. Recent theoretical, modeling, and observational advances have revealed new dynamical properties of the ASC, making it timely to review. Earlier reviews of the ASC focused largely on local classifications of water properties of the ASC's primary front. Here we instead provide a classification of the current's frontal structure based on the dynamical mechanisms that govern both the along‐slope and cross‐slope circulation; these two modes of circulation are strongly coupled, similar to the Antarctic Circumpolar Current. Highly variable motions, such as dense overflows, tides, and eddies are shown to be critical components of cross‐slope and cross‐shelf exchange, but understanding of how the distribution and intensity of these processes will evolve in a changing climate remains poor due to observational and modeling limitations. Results linking the ASC to larger modes of climate variability, such as El Niño, show that the ASC is an integral part of global climate. An improved dynamical understanding of the ASC is still needed to accurately model and predict future Antarctic sea ice extent, the stability of the Antarctic ice sheets, and the Southern Ocean's contribution to the global carbon cycle.

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The southern ocean meridional overturning in the sea-ice sector is driven by freshwater fluxes

Cited by 90 publications

References 48 publications

The Regulation of Sea Ice Thickness by Double‐Diffusive Processes in the Ross Gyre

The Regulation of Sea Ice Thickness by Double‐Diffusive Processes in the Ross Gyre

The Effect of Air‐Sea Flux Products, Shortwave Radiation Depth Penetration, and Albedo on the Upper Ocean Overturning Circulation

The Antarctic Slope Current in a Changing Climate

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