Oceanic controls on the climate response timescales
Abstract
For several years after an abrupt increase in radiative forcing, climate models characteristically simulate a rapid surface warming. Thereafter, warming slows significantly towards a rate that persists for centuries. The robust separation of a "fast" and "slow" warming response is generally understood as the adjustment of the shallow surface ocean and the vast, isolated deep ocean, respectively. However, the physical processes that set the relative heat capacities of the surface and deep ocean, and control the coupling between these reservoirs, are highly uncertain. This uncertainty stems, in large part, from the complex spatial and temporal heterogeneity of ocean heat uptake.
Here we disentangle the complex physical processes that set the response timescales of the global ocean. To do so, we construct a Green's Function representation of the UVIC ESCM with a novel heat flux boundary condition. Relying on the linearity of this framework, we first deconstruct the global ocean circulation into independent regional components, quantifying how regional processes pace global ocean warming. Secondly, we explore how these local controls are modulated by the spatial pattern of radiative forcing. Finally, we explore a third, fundamental interaction underlying the coupled climate response: the covariance of regional ocean heat uptake processes and the spatial patterns of radiative feedbacks at the ocean surface. In doing so, we identify a third innate response timescale in the system, set by the slow equilibration of the high-latitude ocean as it modifies global radiative adjustment through its influence on local feedbacks.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A21N2757N
- Keywords:
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- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSES;
- 1620 Climate dynamics;
- GLOBAL CHANGE;
- 1622 Earth system modeling;
- GLOBAL CHANGE;
- 1630 Impacts of global change;
- GLOBAL CHANGE