Preconditioning of the Weddell Sea Polynya by the Ocean Mesoscale and Dense Water Overflows

Dufour, Carolina O.; Morrison, Adele K.; Griffies, Stephen M.; Frenger, Ivy; Zanowski, Hannah; Winton, Michael

doi:10.1175/jcli-d-16-0586.1

Cited by 83 publications

(120 citation statements)

References 63 publications

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“…Azaneu et al (2014) discussed the possible triggers of the ECCO2 polynya and suggested that the long-term warming of the bottom waters was one of the main factors that contributed to the polynya establishment and subsequent expansion. Long-term warming of bottom waters has been pointed out as a trend also in other nonassimilatory models, such as the Kiel Climate Model and climate models CM2.5 and CM2.6 (Dufour et al, 2017), and in both studies the heat buffered has opened a polynya in the Weddell Sea. In addition, both ECCO2 and SoSE use the same ocean model and similar modeling frameworks, so we cannot rule out the appearance of the polynya in both models as an expression of similar model features of the reanalysis products.…”

Section: The Polynya Begins To Open In November 2003mentioning

confidence: 77%

On deep convection events and Antarctic Bottom Water formation in ocean reanalysis products

2017

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Abstract. Open ocean deep convection is a common source of error in the representation of Antarctic Bottom Water (AABW) formation in ocean general circulation models. Although those events are well described in non-assimilatory ocean simulations, the recent appearance of a massive open ocean polynya in the Estimating the Circulation and Climate of the Ocean Phase II reanalysis product (ECCO2) raises questions on which mechanisms are responsible for those spurious events and whether they are also present in other state-of-the-art assimilatory reanalysis products. To investigate this issue, we evaluate how three recently released high-resolution ocean reanalysis products form AABW in their simulations. We found that two of the products create AABW by open ocean deep convection events in the Weddell Sea that are triggered by the interaction of sea ice with the Warm Deep Water, which shows that the assimilation of sea ice is not enough to avoid the appearance of open ocean polynyas. The third reanalysis, My Ocean University Reading UR025.4, creates AABW using a rather dynamically accurate mechanism. The UR025.4 product depicts both continental shelf convection and the export of Dense Shelf Water to the open ocean. Although the accuracy of the AABW formation in this reanalysis product represents an advancement in the representation of the Southern Ocean dynamics, the differences between the real and simulated processes suggest that substantial improvements in the ocean reanalysis products are still needed to accurately represent AABW formation.

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Section: The Polynya Begins To Open In November 2003mentioning

confidence: 77%

On deep convection events and Antarctic Bottom Water formation in ocean reanalysis products

2017

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“…Stewart and Thompson () further showed that as the winds and wind‐driven DSW export weaken, the generation of eddies and eddy‐driven DSW export intensify to compensate, leaving the overall DSW export relatively insensitive to the along‐slope winds. Recent studies have also indicated a role for eddies in mediating DSW export to the wider Southern Ocean by mediating the stratification of the ASF around the Weddell Gyre and its response to variable wind forcing (Daae et al, ; Dufour et al, ; Su et al, ).…”

Section: Dynamics and Variability Of The Ascmentioning

confidence: 99%

The Antarctic Slope Current in a Changing Climate

Thompson

Stewart

Spence

et al. 2018

Reviews of Geophysics

271

330

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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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“…Furthermore, it has been argued that the occasional but periodic opening of the Weddell Polynya (Carsey, ), an area of open water of up to 3 × 10 5 km 2 , which appeared in winters of 1974–1976 and again in 2016 and 2017, can short‐circuit the usual deep‐water formation processes by rapid open ocean buoyancy loss and deep convection. However, recent literature (e.g., Dufour et al, ) has emphasized the importance both of an interior heat reservoir and of mesoscale eddy activity on triggering polynya development. It has also been suggested that a prolonged negative phase of the Southern Annular Mode (SAM) might be implicated in allowing the polynya to open (Gordon et al, ).…”

Section: Physical Oceanographymentioning

confidence: 99%

“…High resolution is needed to simulate the fluxes between the flows under the Filchner‐Ronne Ice Shelf, the continental shelf waters, the interior WG, and the ACC. Polynyas in coastal and open‐ocean regions have lasting profound effects on the atmosphere and ocean state, yet they are often inadequately represented in numerical models (Dufour et al, ). Challenges to modeling the WG go far deeper, however, than simply an issue of resolution.…”

Section: Modeling the Wgmentioning

confidence: 99%

The Weddell Gyre, Southern Ocean: Present Knowledge and Future Challenges

Vernet

Geibert

Hoppema

et al. 2019

Reviews of Geophysics

154

147

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The Weddell Gyre (WG) is one of the main oceanographic features of the Southern Ocean south of the Antarctic Circumpolar Current which plays an influential role in global ocean circulation as well as gas exchange with the atmosphere. We review the state‐of‐the art knowledge concerning the WG from an interdisciplinary perspective, uncovering critical aspects needed to understand this system's role in shaping the future evolution of oceanic heat and carbon uptake over the next decades. The main limitations in our knowledge are related to the conditions in this extreme and remote environment, where the polar night, very low air temperatures, and presence of sea ice year‐round hamper field and remotely sensed measurements. We highlight the importance of winter and under‐ice conditions in the southern WG, the role that new technology will play to overcome present‐day sampling limitations, the importance of the WG connectivity to the low‐latitude oceans and atmosphere, and the expected intensification of the WG circulation as the westerly winds intensify. Greater international cooperation is needed to define key sampling locations that can be visited by any research vessel in the region. Existing transects sampled since the 1980s along the Prime Meridian and along an East‐West section at ~62°S should be maintained with regularity to provide answers to the relevant questions. This approach will provide long‐term data to determine trends and will improve representation of processes for regional, Antarctic‐wide, and global modeling efforts—thereby enhancing predictions of the WG in global ocean circulation and climate.

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Preconditioning of the Weddell Sea Polynya by the Ocean Mesoscale and Dense Water Overflows

Cited by 83 publications

References 63 publications

On deep convection events and Antarctic Bottom Water formation in ocean reanalysis products

On deep convection events and Antarctic Bottom Water formation in ocean reanalysis products

The Antarctic Slope Current in a Changing Climate

The Weddell Gyre, Southern Ocean: Present Knowledge and Future Challenges

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