The Role of Oceans and Sea Ice in Abrupt Transitions between Multiple Climate States

Rose, Brian E. J.; Ferreira, David; Marshall, John

doi:10.1175/jcli-d-12-00175.1

Cited by 49 publications

(45 citation statements)

References 59 publications

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“…There are of course some limitations to this perspective. Large climate changes involving significant changes in sea ice extent can involve demonstrably non-linear threshold and hysteresis behavior [20,52,54]. However, there is little evidence of such threshold behavior in future global warming scenarios [5].…”

Section: Efficacy Of a Climate Forcing And Additive Responsesmentioning

confidence: 99%

The Effects of Ocean Heat Uptake on Transient Climate Sensitivity

Rose

Rayborn

2016

Curr Clim Change Rep

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Transient climate sensitivity tends to increase on multiple timescales in climate models subject to an abrupt CO 2 increase. The interdependence of radiative and ocean heat uptake processes governing this increase are reviewed. Heat uptake tends to be spatially localized to the subpolar oceans, and this pattern emerges rapidly from an initially uniform distribution. Global climatic impact of heat uptake is studied through the lens of the efficacy concept and a linear systems perspective in which responses to individual climate forcing agents are additive. Heat uptake can be treated as a slowly varying forcing on the atmosphere and surface, whose efficacy is strongly determined by its geographical pattern. An illustrative linear model driven by simple prescribed uptake patterns demonstrates the emergence of increasing climate sensitivity as a consequence of the slow decay of high-efficacy subpolar heat uptake. Evidence is reviewed for the key role of shortwave cloud feedbacks in setting the high efficacy of ocean heat uptake and thus in increasing climate sensitivity. A causal physical mechanism is proposed, linking subpolar heat uptake to a global-scale increase in lower-tropospheric stability. It is shown that the rate of increase in estimated inversion strength systematically slows as heat uptake decays. Variations in heat uptake should therefore manifest themselves as differences in low cloud feedbacks.

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Section: Efficacy Of a Climate Forcing And Additive Responsesmentioning

confidence: 99%

The Effects of Ocean Heat Uptake on Transient Climate Sensitivity

Rose

Rayborn

2016

Curr Clim Change Rep

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“…After imposing external perturbations sea ice (16) and AMOC (27) can undergo abrupt transitions between multiple equilibria. The changes we described above had a different origin, and the resulting cooling over Europe was similar (28).…”

Section: Uniqueness Of the Abrupt Changementioning

confidence: 99%

“…In many studies that addressed this relationship, atmospheric feedbacks were either absent, or crudely represented. It was implied that a larger response or sensitivity might be acquired with more complete atmospheric dynamics (16). A climate model with sufficient atmospheric feedbacks and a sensitive sea-ice component…”

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confidence: 99%

Spontaneous abrupt climate change due to an atmospheric blocking–sea-ice–ocean feedback in an unforced climate model simulation

Drijfhout

Gleeson

Dijkstra

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a highresolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70°N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change.climate modeling | thermohaline circulation | Great Salinity Anomaly A common definition of abrupt climate change is that the climate is undergoing a transition at a faster rate than changes in the external forcing. Dansgaard-Oeschger (DO) events are the iconic examples of such abrupt climate change, featuring the last glacial period as recorded in Greenland ice cores (1). DO events have been linked to large variations of the Atlantic meridional overturning circulation (AMOC), forced by freshwater input into the North Atlantic (2). This theory has been corroborated by results from coarse-resolution climate models with simplified atmospheric dynamics (3, 4). However, more sophisticated climate models show a temperature response that is still weak compared with DO events (5), even in the case of unrealistically large freshwater forcing. Recently, it has been argued that sea ice might play a key role in the onset of DO events (6, 7). A displacement of the ice edge rapidly changes the amount of absorbed shortwave radiation due to the ice-albedo feedback, but also it reduces heat release from the ocean to the atmosphere. Both processes cool the atmosphere and the ocean surface. Series of interactions between ocean and cryosphere may build and erode a freshwater halocline in the Nordic seas, promoting large changes in sea ice that can be associated with changes between cold stadials and warm interstadials (8). In this scenario, the AMOC continues to...

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“…For example, in a complex general-circulation model with current continental distribution and solar insolation, Marotzke and Botzet (2007) identified a globally icecovered stable state analogous of the "Snowball Earth" conditions in the Neoproterozoic . Ferreira et al (2011) and Rose et al (2013) even found three stable states in a complex model with idealised ocean geometry. Climate variability plays an important role for the likelihood of transitions between such states, and for their reversibility (Lee and North, 1995), and thus needs to be considered to understand the evolution of climate in the Earth's deep past.…”

Section: Introductionmentioning

confidence: 98%

Statistical indicators of Arctic sea-ice stability – prospects and limitations

et al. 2016

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Abstract. We examine the relationship between the mean and the variability of Arctic sea-ice coverage and volume in a large range of climates from globally ice-covered to globally ice-free conditions. Using a hierarchy of two column models and several comprehensive Earth system models, we consolidate the results of earlier studies and show that mechanisms found in simple models also dominate the interannual variability of Arctic sea ice in complex models. In contrast to predictions based on very idealised dynamical systems, we find a consistent and robust decrease of variance and autocorrelation of sea-ice volume before summer sea ice is lost. We attribute this to the fact that thinner ice can adjust more quickly to perturbations. Thereafter, the autocorrelation increases, mainly because it becomes dominated by the ocean water's large heat capacity when the ice-free season becomes longer. We show that these changes are robust to the nature and origin of climate variability in the models and do not depend on whether Arctic sea-ice loss occurs abruptly or irreversibly. We also show that our climate is changing too rapidly to detect reliable changes in autocorrelation of annual time series. Based on these results, the prospects of detecting statistical early warning signals before an abrupt sea-ice loss at a "tipping point" seem very limited. However, the robust relation between state and variability can be useful to build simple stochastic climate models and to make inferences about past and future sea-ice variability from only short observations or reconstructions.

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The Role of Oceans and Sea Ice in Abrupt Transitions between Multiple Climate States

Cited by 49 publications

References 59 publications

The Effects of Ocean Heat Uptake on Transient Climate Sensitivity

The Effects of Ocean Heat Uptake on Transient Climate Sensitivity

Spontaneous abrupt climate change due to an atmospheric blocking–sea-ice–ocean feedback in an unforced climate model simulation

Statistical indicators of Arctic sea-ice stability – prospects and limitations

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