TY - JOUR
T1 - Abrupt regime shifts in the North Atlantic atmospheric circulation over the last deglaciation
AU - Löfverström, Marcus
AU - Lora, Juan M.
N1 - Funding Information:
We acknowledge F. He, Z. Liu, B. Otto-Bliesner, and their collaborators for producing and making publicly available the TraCE-21k simulation. We also thank Paul Valdes and Xu Zhang for constructive reviews that improved the quality of this study. The National Center for Atmospheric Research (NCAR) is sponsored by the U.S. National Science Foundation (NSF). M.L. is supported by the U.S. Department of Energy (DOE), Office of Science (BER) award DE-SC0012606, and J.M.L. acknowledges support from the National Science Foundation fellowship AGS-PRF-1524866. Data used in this study were produced on computing resources provided by the Climate Simulation Laboratory at NCAR’s Computational and Information Systems Laboratory (https://www2.cisl.ucar.edu/), sponsored by the National Science Foundation and other agencies, and are freely available on the Earth System Grid (https://www.earthsystemgrid.org/).
Publisher Copyright:
©2017. American Geophysical Union. All Rights Reserved.
PY - 2017/8/16
Y1 - 2017/8/16
N2 - 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.
AB - 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.
KW - atmosphere-ice sheet interactions
KW - circulation regimes
KW - deglacial climate
KW - jet stream
KW - planetary wave reflection
KW - stationary waves
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U2 - 10.1002/2017GL074274
DO - 10.1002/2017GL074274
M3 - Article
AN - SCOPUS:85028401929
VL - 44
SP - 8047
EP - 8055
JO - Geophysical Research Letters
JF - Geophysical Research Letters
SN - 0094-8276
IS - 15
ER -