The ocean's role in the coupled climate response to high-latitude forcing
Abstract
Using a set of coupled climate model simulations with robust near-surface atmospheric responses to sea-ice loss, the ocean's response to ice loss within the broader global warming process is examined. The atmospheric response is not only robust to inter-model differences but also to differences in sea-ice loss protocols. While it has previously been shown that a fully dynamical ocean component is required to obtain a robust atmospheric response and despite the aforementioned consistency in the atmospheric response, the ocean's response is quite disparate, particularly in the climatically sensitive subpolar North Atlantic region.
Using a pattern-scaling approach, the additivity of atmospheric responses to lower and higher latitude forcings is exploited, thus removing the cross-coupling between tropical and high-latitude responses. Whether this approach is valid in the ocean at the surface is explored. Regardless of whether scaling is applied or not, we find that there is little consistency in the ocean's response. A warming of the sea surface occurs in all seasons in the Arctic and subpolar seas where ice is lost and most models also show an SST gradient in the Pacific Ocean indicative of a positive PDO-type pattern. Some models also find a cooling of the North Atlantic that scales with sea-ice loss, however the location of cooling is particular to a given model. Most models find a robust freshening of the Arctic Ocean as a result of the sea-ice melt. Surprisingly, most of this freshening appears to scale with and hence be more controlled by lower latitude warming than by sea ice loss. In addition, some salinification patterns scaling with sea-ice loss are robust, e.g. in Hudson's Bay. The way in which the circulation and mixed-layer depth responds in the North Atlantic to sea-ice loss and to lower latitude warming is model-dependent and/or dependent on the forcing method. Finally, while all models drive a decrease in the strength of the Atlantic Meridional Overturning Circulation, there is little consensus amongst the models regarding how strong of a role this would play relative to the warming response.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C23D1598H
- Keywords:
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- 3349 Polar meteorology;
- ATMOSPHERIC PROCESSES;
- 0456 Life in extreme environments;
- BIOGEOSCIENCES;
- 0750 Sea ice;
- CRYOSPHERE;
- 1620 Climate dynamics;
- GLOBAL CHANGE;
- 1621 Cryospheric change;
- GLOBAL CHANGE;
- 1622 Earth system modeling;
- GLOBAL CHANGE;
- 1694 Instruments and techniques;
- GLOBAL CHANGE;
- 4207 Arctic and Antarctic oceanography;
- OCEANOGRAPHY: GENERAL