Publication Abstracts

Orbe et al. 2022, submitted

Orbe, C., D. Rind, R.L. Miller, L. Nazarenko, A. Romanou, J. Jonas, G. Russell, M. Kelley, and G. Schmidt, 2022: Atmospheric response to a collapse of the North Atlantic circulation under a mid-range future climate scenario: A regime shift in Northern Hemisphere dynamics. J. Climate, submitted.

Climate models project a future weakening of the Atlantic Meridional Overturning Circulation (AMOC), but the impacts of this weakening on climate remain highly uncertain. A key challenge in quantifying the impact of an AMOC decline is in isolating its impact, relative to other changes related to increased greenhouse gases. Here we isolate the climate impacts of a weakened AMOC in the broader context of a warming climate using a unique ensemble of SSP 2-4.5 integrations that was performed using the CMIP6 version of the NASA Goddard Institute for Space Studies ModelE (E2.1). In these runs internal variability alone results in a spontaneous bifurcation of the ocean flow, wherein two out of ten ensemble members exhibit an entire AMOC collapse, while the other eight recover at various stages despite identical forcing of each ensemble member. We show that an AMOC collapse results in an abrupt northward shift and strengthening of the Northern Hemisphere (NH) Hadley Cell and intensification of the northern midlatitude jet. We then use a set of coupled atmosphere-ocean abrupt CO2 experiments spanning 1-8×CO2 to show that this response to an AMOC collapse results in a nonlinear shift in the NH circulation moving from 2 to 3×CO2. Slab-ocean versions of these experiments, by comparison, do not capture this nonlinear behavior. Our results suggest that changes in ocean heat flux convergences associated with an AMOC collapse can result in profound changes in the NH circulation and continued efforts to constrain the AMOC response to future climate change are needed.

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BibTeX Citation

@unpublished{or05200z,
  author={Orbe, C. and Rind, D. and Miller, R. L. and Nazarenko, L. and Romanou, A. and Jonas, J. and Russell, G. and Kelley, M. and Schmidt, G.},
  title={Atmospheric response to a collapse of the North Atlantic circulation under a mid-range future climate scenario: A regime shift in Northern Hemisphere dynamics},
  year={2022},
  journal={J. Climate},
  note={Manuscript submitted for publication}
}

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RIS Citation

TY  - UNPB
ID  - or05200z
AU  - Orbe, C.
AU  - Rind, D.
AU  - Miller, R. L.
AU  - Nazarenko, L.
AU  - Romanou, A.
AU  - Jonas, J.
AU  - Russell, G.
AU  - Kelley, M.
AU  - Schmidt, G.
PY  - 2022
TI  - Atmospheric response to a collapse of the North Atlantic circulation under a mid-range future climate scenario: A regime shift in Northern Hemisphere dynamics
JA  - J. Climate
ER  -

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