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Title: Abrupt regime shifts in the North Atlantic atmospheric circulation over the last deglaciation

Here, we analyze modeling results of the North Atlantic atmospheric winter circulation from a transient climate simulation over the last 21,000 years. In agreement with previous studies, we find that the midlatitude jet stream assumes a strong, stable, and zonal disposition so long as the North American ice sheets remain in their continent-wide Last Glacial Maximum (LGM) configuration. However, when the Laurentide ice sheet (LIS) and Cordilleran ice sheet separate (~14,000 years ago), the jet stream abruptly changes to a tilted circulation regime, similar to modern. The proposed explanation is that the dominant stationary wave source in the North Atlantic sector changes from the LIS to the Cordilleran mountain range during the saddle collapse. As long as the LIS dominates, the circulation retains the zonal LGM state characterized by prevalent stationary wave reflection in the subtropical North Atlantic. When the Cordillera takes over, the circulation acquires its modern disposition with a weak and meridionally tilted jet stream and storm track.
Authors:
ORCiD logo [1] ; ORCiD logo [2]
  1. National Center for Atmospheric Research (NCAR), Boulder, CO (United States)
  2. Univ. of California, Los Angeles, CA (United States). Dept. of Earth, Planetary, and Space Sciences
Publication Date:
Grant/Contract Number:
SC0012606; AGS‐PRF‐1524866
Type:
Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 44; Journal Issue: 15; Journal ID: ISSN 0094-8276
Publisher:
American Geophysical Union
Research Org:
National Center for Atmospheric Research (NCAR), Boulder, CO (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; deglacial climate; jet stream; stationary waves; atmosphere-ice sheet interactions; circulation regimes; planetary wave reflection
OSTI Identifier:
1473897
Alternate Identifier(s):
OSTI ID: 1374905

Löfverström, Marcus, and Lora, Juan M. Abrupt regime shifts in the North Atlantic atmospheric circulation over the last deglaciation. United States: N. p., Web. doi:10.1002/2017GL074274.
Löfverström, Marcus, & Lora, Juan M. Abrupt regime shifts in the North Atlantic atmospheric circulation over the last deglaciation. United States. doi:10.1002/2017GL074274.
Löfverström, Marcus, and Lora, Juan M. 2017. "Abrupt regime shifts in the North Atlantic atmospheric circulation over the last deglaciation". United States. doi:10.1002/2017GL074274. https://www.osti.gov/servlets/purl/1473897.
@article{osti_1473897,
title = {Abrupt regime shifts in the North Atlantic atmospheric circulation over the last deglaciation},
author = {Löfverström, Marcus and Lora, Juan M.},
abstractNote = {Here, we analyze modeling results of the North Atlantic atmospheric winter circulation from a transient climate simulation over the last 21,000 years. In agreement with previous studies, we find that the midlatitude jet stream assumes a strong, stable, and zonal disposition so long as the North American ice sheets remain in their continent-wide Last Glacial Maximum (LGM) configuration. However, when the Laurentide ice sheet (LIS) and Cordilleran ice sheet separate (~14,000 years ago), the jet stream abruptly changes to a tilted circulation regime, similar to modern. The proposed explanation is that the dominant stationary wave source in the North Atlantic sector changes from the LIS to the Cordilleran mountain range during the saddle collapse. As long as the LIS dominates, the circulation retains the zonal LGM state characterized by prevalent stationary wave reflection in the subtropical North Atlantic. When the Cordillera takes over, the circulation acquires its modern disposition with a weak and meridionally tilted jet stream and storm track.},
doi = {10.1002/2017GL074274},
journal = {Geophysical Research Letters},
number = 15,
volume = 44,
place = {United States},
year = {2017},
month = {8}
}