Details:

Journal Title:
Journal of Climate
Personal Author:
Delworth, Thomas L. ; Zeng, Fanrong
Delworth, Thomas L. ; Zeng, Fanrong Less -
NOAA Program & Office:
OAR (Oceanic and Atmospheric Research) ; GFDL (Geophysical Fluid Dynamics Laboratory)
OAR (Oceanic and Atmospheric Research) ; GFDL (Geophysical Fluid Dynamics Laboratory) Less -
Description:
The impact of the North Atlantic Oscillation (NAO) on the Atlantic meridional overturning circulation (AMOC) and large-scale climate is assessed using simulations with three different climate models. Perturbation experiments are conducted in which a pattern of anomalous heat flux corresponding to the NAO is added to the model ocean. Differences between the perturbation experiments and a control illustrate how the model ocean and climate system respond to the NAO. A positive phase of the NAO strengthens the AMOC by extracting heat from the subpolar gyre, thereby increasing deep-water formation, horizontal density gradients, and the AMOC. The flux forcings have the spatial structure of the observed NAO, but the amplitude of the forcing varies in time with distinct periods varying from 2 to 100 yr. The response of the AMOC to NAO variations is small at short time scales but increases up to the dominant time scale of internal AMOC variability (20–30 yr for the models used). The amplitude of the AMOC response, as well as associated oceanic heat transport, is approximately constant as the time scale of the forcing is increased further. In contrast, the response of other properties, such as hemispheric temperature or Arctic sea ice, continues to increase as the time scale of the forcing becomes progressively longer. The larger response is associated with the time integral of the anomalous oceanic heat transport at longer time scales, combined with an increased impact of radiative feedback processes. It is shown that NAO fluctuations, similar in amplitude to those observed over the last century, can modulate hemispheric temperature by several tenths of a degree.
Keywords:
[+]
Circulation Climate Models Decadal Variability North Atlantic Oscillation Variability
Source:
Journal of Climate, 29(3), 941-962
DOI:
https://doi.org/10.1175/JCLI-D-15-0396.1
Document Type:
Journal Article
Place as Subject:
North Atlantic Ocean
Rights Information:
Other
Compliance:
Submitted
Main Document Checksum:
[+]
urn:sha256:69976ab57aad9e8ffb805d492f6e5948a7e1b594b74eca4611fc9e1b6b81b6c7
Download URL:
https://repository.library.noaa.gov/view/noaa/29856/noaa_29856_DS1.pdf
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