Sensitivity of the Atlantic Meridional Overturning Circulation to Different Paleoclimate States Simulated with the Community Earth System Model
Abstract
The Atlantic Meridional Overturning Circulation (AMOC) is a key component of the global ocean circulation influencing climate through transports of heat and freshwater, and its role in the ventilation of the deep ocean on long time scales. The strength and vertical structure of AMOC is hypothesized to be sensitive to multiple driving processes, such as surface buoyancy, wind forcings, and mixing of water masses, all of which are projected to vary under anthropogenic climate change. Earth system models are a useful tool to investigate the mechanisms underlying AMOC sensitivity to climate drivers over a range of timescales and climate conditions.
Previous paleoclimate modeling studies using the Community Earth System Model (CESM) showed that paleoclimate boundary condition changes such as Arctic gateway closures, variations in greenhouse gases, changes in ice-sheet topography, and meltwater discharge into the North Atlantic impact AMOC and associated surface climate. In this study we compare and characterize the response of AMOC to different paleoclimate scenarios simulated with the most recent CESM2 as part of Paleoclimate Model Intercomparison Project, phase 4: the mid-Holocene (6ka), the last interglacial (127ka), the warm mid-Pliocene (3.205Ma), and the last glacial maximum (21ka) periods. We synthesize the AMOC responses to these out-of-sample climate states using different AMOC metrics to facilitate model-data comparisons. We identify key processes and feedbacks underlying the sensitivity of AMOC and the associated global climate impacts. We also assess the impact on AMOC of the enhanced Equilibrium Climate Sensitivity of CESM2 by comparing with simulations done with previous versions of the CESM.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMPP038..06B
- Keywords:
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- 4512 Currents;
- OCEANOGRAPHY: PHYSICAL;
- 4513 Decadal ocean variability;
- OCEANOGRAPHY: PHYSICAL;
- 4901 Abrupt/rapid climate change;
- PALEOCEANOGRAPHY;
- 4912 Biogeochemical cycles;
- processes;
- and modeling;
- PALEOCEANOGRAPHY