Cessation of deep convection in the open Southern Ocean under anthropogenic climate change

Lavergne, Casimir de; Palter, Jaime B.; Galbraith, Eric D.; Bernardello, Raffaele; Marinov, I.

doi:10.1038/nclimate2132

Cited by 258 publications

(322 citation statements)

References 34 publications

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“…Many previous studies investigating the influence of increased freshwater fluxes to the Southern Ocean focus on the impact of changes in precipitation. Our results highlight a limitation of many climate models, including those of CMIP5, as they are unable to simulate freshwater flux changes from increased glacial melt (Lavergne et al 2014;van den Berk and Drijfhout 2014).…”

Section: B Shelf and Deep Ocean Responsementioning

confidence: 87%

Sensitivity of Antarctic Bottom Water to Changes in Surface Buoyancy Fluxes

et al. 2015

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The influence of freshwater and heat flux changes on Antarctic Bottom Water (AABW) properties are investigated within a realistic bathymetry coupled ocean-ice sector model of the Atlantic Ocean. The model simulations are conducted at eddy-permitting resolution where dense shelf water production dominates over open ocean convection in forming AABW. Freshwater and heat flux perturbations are applied independently and have contradictory surface responses, with increased upper-ocean temperature and reduced ice formation under heating and the opposite under increased freshwater fluxes. AABW transport into the abyssal ocean reduces under both flux changes, with the reduction in transport being proportional to the net buoyancy flux anomaly south of 608S.Through inclusion of shelf-sourced AABW, a process absent from most current generation climate models, cooling and freshening of dense source water is facilitated via reduced on-shelf/off-shelf exchange flow. Such cooling is propagated to the abyssal ocean, while compensating warming in the deep ocean under heating introduces a decadal-scale variability of the abyssal water masses. This study emphasizes the fundamental role buoyancy plays in controlling AABW, as well as the importance of the inclusion of shelf-sourced AABW within climate models in order to attain the complete spectrum of possible climate change responses.

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Section: B Shelf and Deep Ocean Responsementioning

confidence: 87%

Sensitivity of Antarctic Bottom Water to Changes in Surface Buoyancy Fluxes

et al. 2015

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“…Above-average SSTs (from the Indian Ocean) may also have contributed by preconditioning the pack ice for polynya formation. Although modest in size compared to the giant polynyas of 1974-76 (Carsey 1980;de Lavergne et al 2014), the 2016 polynya is significant as it may announce a revival of deep ocean convection in the Weddell Sea. The reemergence implies underlying conditions that may have hastened sea ice retreat (Figs.…”

Section: E Seasonal Melt Extent and Duration-l Wang And H Liumentioning

confidence: 99%

State of the Climate in 2016

Aaron-Morrison¹,

Ackerman²,

Adams³

et al. 2017

Bulletin of the American Meteorological Society

150

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“…In a more recent study, Gordon et al (2007) noticed that during long periods of the negative Southern Annular Mode Index (Limpasuvan and Hartmann, 1999), the Weddell Sea had enhanced sea ice formation and brine release, which destabilized the water column and allowed the Weddell Polynya to occur. Lavergne et al (2014) also stated that the reduced occurrence of open ocean deep convection in the Southern Ocean after 1950 was due to strong ice melt and enhanced Southern Ocean stratification, which indicated that strong sea ice seasonality is an important trigger for polynya opening. In that matter, a recent study found that GISS-E2-R and GFDL-ESM22 ocean models from CIMP5 attribute the frequent deep convection events to stronger sea ice seasonality (Heuzé et al, 2015).…”

Section: The Polynya Begins To Open In November 2003mentioning

confidence: 99%

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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Cessation of deep convection in the open Southern Ocean under anthropogenic climate change

Cited by 258 publications

References 34 publications

Sensitivity of Antarctic Bottom Water to Changes in Surface Buoyancy Fluxes

Sensitivity of Antarctic Bottom Water to Changes in Surface Buoyancy Fluxes

State of the Climate in 2016

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

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