North Atlantic climate variability in coupled models and data

• Main Authors: Kravtsov, S. K., Dewar, W. K., Ghil, M., Berloff, P. S., Mcwilliams, J. C.
• Other Authors: Department of Mathematical Sciences, University of Wisconsin - Milwaukee, Department of Atmospheric and Oceanic Sciences Los Angeles (AOS), University of California Los Angeles (UCLA), University of California (UC)-University of California (UC), Dept. of Oceanography, Florida State University Tallahassee (FSU), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Dept. of Physical Oceanography, Woods Hole Oceanographic Institution (WHOI), DAMTP
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2008
• Subjects: [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO]; [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph]; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; North Atlantic
• Online Access: https://hal.science/hal-00331109; https://hal.science/hal-00331109/document; https://hal.science/hal-00331109/file/npg-15-13-2008.pdf

International audience We show that the observed zonally averaged jet in the Northern Hemisphere atmosphere exhibits two spatial patterns with broadband variability in the decadal and inter-decadal range; these patterns are consistent with an important role of local, mid-latitude ocean–atmosphere coupling. A key aspect of this behaviour is the fundamentally nonlinear bi-stability of the atmospheric jet's latitudinal position, which enables relatively small sea-surface temperature anomalies associated with ocean processes to affect the large-scale atmospheric winds. The wind anomalies induce, in turn, complex three-dimensional anomalies in the ocean's main thermocline; in particular, they may be responsible for recently reported cooling of the upper ocean. Both observed modes of variability, decadal and inter-decadal, have been found in our intermediate climate models. One mode resembles North Atlantic tri-polar sea-surface temperature (SST) patterns described elsewhere. The other mode, with mono-polar SST pattern, is novel; its key aspects include interaction of oceanic turbulence with the large-scale oceanic flow. To the extent these anomalies exist, the interpretation of observed climate variability in terms of natural and human-induced changes will be affected. Coupled mid-latitude ocean-atmosphere modes do, however, suggest some degree of predictability is possible.