Abyssal Ocean Warming and Salinification after Weddell Polynyas in the GFDL CM2G Coupled Climate Model

Zanowski, Hannah; Hallberg, Robert; Sarmiento, Jorge L.

doi:10.1175/jpo-d-15-0109.1

Cited by 41 publications

(37 citation statements)

References 69 publications

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“…For example, models that stay in the nonconvective regime only for short periods will contain a larger contribution of convection effects in their stratification strength averaged over the nonconvective periods. Nevertheless, choosing a shorter averaging window, e.g., a decade [ Martin et al , ; Zanowski et al , ], to compute a “nonconvective” reference is not applicable to our multimodel analysis, because in 8 of the 15 models the average length of nonconvective periods is shorter than 8 years.…”

Section: Resultsmentioning

confidence: 99%

Physical controls of Southern Ocean deep‐convection variability in CMIP5 models and the Kiel Climate Model

Reintges

Martin

Latif

et al. 2017

Geophysical Research Letters

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Global climate models exhibit large biases in the Southern Ocean. For example, in models Antarctic bottom water is formed mostly through open‐ocean deep convection rather than through shelf convection. Still, the timescale, region, and intensity of deep‐convection variability vary widely among models. We investigate the physical controls of this variability in the Atlantic sector of the Southern Ocean, where most of the models simulate recurring deep‐convection events. We analyzed output from 11 exemplary CMIP5 models and four versions of the Kiel Climate Model. Of the several potential physical control parameters that we tested, the ones shared by all these models are as follows: Stratification in the convection region influences the timescale of the deep‐convection variability; i.e., models with a strong (weak) stratification vary on long (short) timescales. Also, sea ice volume affects the modeled mean state in the Southern Ocean: Large (small) sea ice volume is associated with a nonconvective (convective) predominant regime.

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Section: Resultsmentioning

confidence: 99%

Physical controls of Southern Ocean deep‐convection variability in CMIP5 models and the Kiel Climate Model

Reintges

Martin

Latif

et al. 2017

Geophysical Research Letters

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“…The added features of these improved modeling platforms provide the opportunity to increase the model time step (via ALE removal of the vertical CFL), reduce spurious numerical mixing (via ALE remapping to continuous isopycnal coordinates), and directly simulate freshwater addition and removal at the ocean surface (enabled in both LVD and EVD through replacing the rigid lid approach of Bryan (1969) with a free surface). Recent examples of successful applications of these techniques are Hofmeister et al (2010), Leclair and Madec (2011), Petersen et al (2015), and Zanowski et al (2015).…”

Section: Vertical Discretizationmentioning

confidence: 99%

Challenges and Prospects in Ocean Circulation Models

et al. 2019

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We revisit the challenges and prospects for ocean circulation models following Griffies et al. (2010). Over the past decade, ocean circulation models evolved through improved understanding, numerics, spatial discretization, grid configurations, parameterizations, data assimilation, environmental monitoring, and process-level observations and modeling. Important large scale applications over the last decade are simulations of the Southern Ocean, the Meridional Overturning Circulation and its variability, and regional sea level change. Submesoscale variability is now routinely resolved in process models and permitted in a few global models, and submesoscale effects are parameterized in most global models. The scales where nonhydrostatic effects become important are beginning to be resolved in regional and process models. Coupling to sea ice, ice shelves, and high-resolution atmospheric models has stimulated new ideas and driven improvements in numerics. Observations have provided insight into turbulence and mixing around the globe and its consequences are assessed through perturbed physics models. Relatedly, parameterizations of the mixing and overturning processes in boundary layers and the ocean interior have improved. New diagnostics being used for evaluating models Fox-Kemper et al. Ocean Circulation Models alongside present and novel observations are briefly referenced. The overall goal is summarizing new developments in ocean modeling, including: how new and existing observations can be used, what modeling challenges remain, and how simulations can be used to support observations.

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“…Because it opens a window between the atmosphere and deep ocean through intense deep convection, the Weddell Sea polynya is thought to have a substantial impact on the climate [see Morales Maqueda et al (2004) for a review], including on the regional atmospheric circulation (e.g., Moore et al 2002), the global overturning circulation (e.g., Martin et al 2013Martin et al , 2015, deep and bottom water properties (e.g., Zanowski et al 2015), and oceanic carbon uptake . That the Weddell Sea polynya was only observed once (Carsey 1980) makes it a feature difficult to fully understand on an observational basis.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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The Weddell Sea polynya is a large opening in the open-ocean sea ice cover associated with intense deep convection in the ocean. A necessary condition to form and maintain a polynya is the presence of a strong subsurface heat reservoir. This study investigates the processes that control the stratification and hence the buildup of the subsurface heat reservoir in the Weddell Sea. To do so, a climate model run for 200 years under preindustrial forcing with two eddying resolutions in the ocean (0.258 CM2.5 and 0.108 CM2.6) is investigated. Over the course of the simulation, CM2.6 develops two polynyas in the Weddell Sea, while CM2.5 exhibits quasi-continuous deep convection but no polynyas, exemplifying that deep convection is not a sufficient condition for a polynya to occur. CM2.5 features a weaker subsurface heat reservoir than CM2.6 owing to weak stratification associated with episodes of gravitational instability and enhanced vertical mixing of heat, resulting in an erosion of the reservoir. In contrast, in CM2.6, the water column is more stably stratified, allowing the subsurface heat reservoir to build up. The enhanced stratification in CM2.6 arises from its refined horizontal grid spacing and resolution of topography, which allows, in particular, a better representation of the restratifying effect by transient mesoscale eddies and of the overflows of dense waters along the continental slope.

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Abyssal Ocean Warming and Salinification after Weddell Polynyas in the GFDL CM2G Coupled Climate Model

Cited by 41 publications

References 69 publications

Physical controls of Southern Ocean deep‐convection variability in CMIP5 models and the Kiel Climate Model

Physical controls of Southern Ocean deep‐convection variability in CMIP5 models and the Kiel Climate Model

Challenges and Prospects in Ocean Circulation Models

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

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