North Atlantic Simulations in Coordinated Ocean-ice Reference Experiments phase II (CORE-II): Inter-Annual to Decadal Variability
Abstract
Simulated inter-annual to decadal variability and trends in the North Atlantic for the1958-2007 period from twenty global ocean - sea-ice coupled models are presented.These simulations are performed as contributions to the second phase of the CoordinatedOcean-ice Reference Experiments (CORE-II). A major focus of the present study is the representation of Atlanticmeridional overturning circulation (AMOC) variability in the participating models.Relationships between AMOC variability and those of some other related variables, suchas subpolar mixed layer depths, the North Atlantic Oscillation (NAO), and the LabradorSea upper-ocean hydrographic properties, are also investigated. In general, AMOCvariability shows three distinct stages. During the first stage that lasts until the mid-to late-1970s, AMOC is relatively steady, remaining lower than its long-term(1958-2007) mean. Thereafter, AMOC intensifies with maximum transports achieved in the mid- to late-1990s. This enhancement isthen followed by a weakening trend until the end of our integration period. Thissequence of low frequency AMOC variability is consistent with previous studies.Regarding strengthening of AMOC between about the mid-1970s and the mid-1990s, our resultssupport a previously identified variability mechanism where AMOC intensification isconnected to increased deep water formation in the subpolar North Atlantic, drivenby NAO-related surface fluxes. The simulations tend to show general agreement in theirrepresentations of, for example, AMOC, sea surface temperature (SST), and subpolar mixed layerdepth variabilities. In particular, the observed variability of the North Atlantic SSTs iscaptured well by all models. These findings indicate that simulated variability andtrends are primarily dictated by the atmospheric datasets which include the influenceof ocean dynamics from nature superimposed onto anthropogenic effects. Despite thesegeneral agreements, there are many differences among the model solutions, particularly in the spatial structures of variabilitypatterns. For example, the location of the maximum AMOC variability differs among themodels between Northern and Southern Hemispheres.
- Publication:
-
American Geophysical Union, Ocean Sciences Meeting
- Pub Date:
- February 2016
- Bibcode:
- 2016AGUOSPO43A..07D
- Keywords:
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- 1616 Climate variability;
- GLOBAL CHANGEDE: 4255 Numerical modeling;
- OCEANOGRAPHY: GENERALDE: 4262 Ocean observing systems;
- OCEANOGRAPHY: GENERALDE: 4513 Decadal ocean variability;
- OCEANOGRAPHY: PHYSICAL