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Abstract Building on previous work using single-basin models, we here explore the time-dependent response of the Atlantic meridional overturning circulation (AMOC) to a sudden global temperature change in a two-basin ocean–ice model. We find that the previously identified mechanisms remain qualitatively useful to explain the transient and the long-term time-mean responses of the AMOC in our simulations. Specifically, we find an initial weakening of the AMOC in response to warming (and vice versa for cooling), controlled by the mid-depth meridional temperature contrast across the Atlantic basin. The long-term mean response instead is controlled primarily by changes in the abyssal stratification within the basin. In contrast to previous studies we find that for small-amplitude surface temperature changes, the equilibrium AMOC is almost unchanged, as the abyssal stratification remains similar due to a substantial compensation between the effects of salinity and temperature changes. The temperature-driven stratification change results from the differential warming/cooling between North Atlantic Deep Water and Antarctic Bottom Water, while the salinity change is driven by changes in Antarctic sea ice formation. Another distinct feature of our simulations is the emergence of AMOC variability in the much colder and much warmer climates. We discuss how this variability is related to variations in deep-ocean heat content, surface salinity, and sea ice in the deep convective regions, both in the North Atlantic and in the Southern Ocean, and its potential relevance to past and future climates.
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This content will become publicly available on July 1, 2026
A Simple Model for Global Temperature Control on Dansgaard–Oeschger Oscillations
During the last glacial period, the Northern Hemisphere climate underwent dramatic swings between relatively warm periods and cold periods—the Dansgaard–Oeschger oscillations. Here, we use recent progress in our theoretical understanding of the Atlantic meridional overturning circulation to develop a simple predictive model that relates variations in the overturning circulation to rapid changes in North Atlantic sea ice and the gradual recharge and discharge of the deep ocean temperature. The robustness of the model is tested against results from idealized general circulation model simulations, and exploration of its parameter space provides insights into the mechanisms dictating the overturning circulation’s response to atmospheric forcing variations. The theoretical model predicts that global atmospheric temperature and salinity fluxes control the relative length of stadial versus interstadial conditions and reproduces the evolving characteristics of theδ18O isotope ice core record over the last 100 kyr when forced only by the slowly changing global mean temperature. The findings indicate that the prominent climate variability observed in the Greenland ice cores is directly influenced by the gradual evolution of global temperatures and salinity fluxes. This variability can be attributed to a relatively simple physical mechanism that involves the interplay of fast positive sea ice and salt-advection feedbacks, along with a delayed negative deep-ocean-temperature feedback.
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- Award ID(s):
- 1846821
- PAR ID:
- 10643552
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Journal of Climate
- Volume:
- 38
- Issue:
- 13
- ISSN:
- 0894-8755
- Page Range / eLocation ID:
- 3169 to 3184
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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