How does internal variability influence the ability of CMIP5 models to reproduce the recent trend in Southern Ocean sea ice extent?

Zunz, Violette; Goosse, Hugues; Massonnet, François

doi:10.5194/tc-7-451-2013

Cited by 156 publications

(177 citation statements)

References 53 publications

(73 reference statements)

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“…However, when forced by estimates of observed external forcing the climate models, which participated in phase 3 of the Coupled Model Intercomparison Project (CMIP3), in the ensemble mean simulate surface warming everywhere over the Southern Ocean during 1979-2005(Hegerl et al 2007.6), whereas surface cooling was observed over large parts of the Southern Ocean during this time. The same holds for the Antarctic sea ice extent, which is simulated to retreat during the recent decades by most CMIP5 models as discussed by Zunz et al (2013). The differences between the models and observations could be caused by internal variability, which can temporarily offset the effects of global warming.…”

Section: Introductionmentioning

confidence: 71%

Southern Ocean Sector Centennial Climate Variability and Recent Decadal Trends

2013

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Evidence is presented for the notion that some contribution to the recent decadal trends observed in the Southern Hemisphere, including the lack of a strong Southern Ocean surface warming, may have originated from longer-term internal centennial variability originating in the Southern Ocean. The existence of such centennial variability is supported by the instrumental sea surface temperatures (SSTs), a multimillennial reconstruction of Tasmanian summer temperatures from tree rings, and a millennial control integration of the Kiel Climate Model (KCM). The model variability was previously shown to be linked to changes in Weddell Sea deep convection. During phases of deep convection the surface Southern Ocean warms, the abyssal Southern Ocean cools, Antarctic sea ice extent retreats, and the low-level atmospheric circulation over the Southern Ocean weakens. After the halt of deep convection the surface Southern Ocean cools, the abyssal Southern Ocean warms, Antarctic sea ice expands, and the low-level atmospheric circulation over the Southern Ocean intensifies, consistent with what has been observed during the recent decades. A strong sensitivity of the time scale to model formulation is noted. In the KCM, the centennial variability is associated with global-average surface air temperature (SAT) changes of the order of a few tenths of a degree per century. The model results thus suggest that internal centennial variability originating in the Southern Ocean should be considered in addition to other internal variability and external forcing when discussing the climate of the twentieth century and projecting that of the twenty-first century.

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Section: Introductionmentioning

confidence: 71%

Southern Ocean Sector Centennial Climate Variability and Recent Decadal Trends

2013

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“…The current generation of climate models almost all fail to capture this increase, while the decrease in Arctic sea ice is much better reproduced Zunz et al, 2013;Shu et al, 2015], suggesting that the models poorly represent the physical process's governing Antarctic sea ice. Moreover, considerable uncertainty still exists as to whether this increase is caused by natural variability or anthropogenic forcings (or some combination), as these factors are known to induce changes to Antarctic sea ice by altering the atmospheric circulation [Yuan and Martinson, 2001;Stammerjohn et al, 2008;Turner et al, 2009;Simpkins et al, 2012;Polvani and Smith, 2013;Zunz et al, 2013;Barnes et al, 2014;Li et al, 2014;Ferreira et al, 2015;Meehl et al, 2016].…”

Section: Introductionmentioning

confidence: 99%

The impacts of El Niño on the observed sea ice budget of West Antarctica

Pope

Holland

Orr

et al. 2017

Geophysical Research Letters

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We assess the impact of El Niño‐induced wind changes on seasonal West Antarctic sea ice concentrations using reanalysis data and sea ice observations. A novel ice budget analysis reveals that in autumn a previously identified east‐west dipole of sea ice concentration anomalies is formed by dynamic and thermodynamic processes in response to El Niño‐generated circulation changes. The dipole features decreased (increased) concentration in the Ross Sea (Amundsen and Bellingshausen Seas). Thermodynamic processes and feedback make a substantial contribution to ice anomalies in all seasons. The eastward propagation of this anomaly is partly driven by mean sea ice drift rather than anomalous winds. Our results demonstrate that linkages between sea ice anomalies and atmospheric variability are highly nonlocal in space and time. Therefore, we assert that caution should be applied when interpreting the results of studies that attribute sea ice changes without accounting for such temporally and spatially remote linkages.

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“…Finally, the observed cooling of SST around Antarctica is postulated to be only an initial response to atmospheric changes and may indeed lead to warming in future periods (Marshall et al 2014;Ferreira et al 2015). The role of internal variability in the current observations also remains unclear (Zunz et al 2013). It has been proposed that these recent observational trends may in fact originate from internal variability on decadal to centennial time scales Latif et al 2013;Zunz et al 2013;Fan et al 2014) rather than external anthropogenic influences.…”

mentioning

confidence: 99%

“…The role of internal variability in the current observations also remains unclear (Zunz et al 2013). It has been proposed that these recent observational trends may in fact originate from internal variability on decadal to centennial time scales Latif et al 2013;Zunz et al 2013;Fan et al 2014) rather than external anthropogenic influences.…”

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confidence: 99%

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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How does internal variability influence the ability of CMIP5 models to reproduce the recent trend in Southern Ocean sea ice extent?

Cited by 156 publications

References 53 publications

Southern Ocean Sector Centennial Climate Variability and Recent Decadal Trends

Southern Ocean Sector Centennial Climate Variability and Recent Decadal Trends

The impacts of El Niño on the observed sea ice budget of West Antarctica

Sensitivity of Antarctic Bottom Water to Changes in Surface Buoyancy Fluxes

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