During the 1976 climate regime shift, the Aleutian low deepened. Many studies have
shown that the oceanic shift was mainly driven by the atmospheric dynamics. In this
thesis numerical studies to investigate the oceanic interdecadal variation as the result of
the 1976 climate shift have been carried out with the GFDL OGCM. Two interdecadal
experiments are performed. One is forced by monthly wind stress climatology for 1976-
1988 and relaxed to monthly SST climatology from the same time period. The other is
forced by monthly wind stress climatology for 1952-1975 and monthly SST climatology
from the same time period. The same sea surface salinity monthly climatology data is
used throughout all the experiments.
The simulated ocean circulations exhibit significant interdecadal variations. The gyre
circulations are spun up both in the subarctic region and the subtropical region, except
in the northern and eastern part of the Gulf of Alaska where the gyral circulation is
weakened.
The large scale surface cooling in the central North Pacific and the warming along
the west coast of North America are simulated. The intensified surface Ekman drifts are
very important in generating the thermal variation near the surface, especially in mid
and high latitudes.
The deepening of the Aleutian Low generates stronger surface divergence in the subarctic
area and stronger convergence in the subtropic. Consequently the upwelhng in
the subarctic region is increased, with a maximum increase of 108% at a depth of 60 m.
The downwelling in the subtropical area is enhanced as well. Along the coast of North
America above 40°7Y, there is an increase in downwelling, which is consistent with the weakening of the Alaskan gyre. The significant variations in upwelling in the subarctic
and downwelling in subtropical regions are confined approximately above a few hundred
meters depth. By working with the large vertical temperature gradients, they produce
large scale subsurface thermal variation, with the cooling in the subarctic and warming
in the subtropic. The depth range of the subsurface thermal variation is limited to above
650 m depth.
The meridional circulation and heat transport are changed consequently. In low latitudes
the poleward heat transport is increased. In the mid latitudes the equatorward heat
transport is increased and mainly contributed by the meridional component, though the
gyre and diffusion components are not negligible. The heat transport in high latitudes,
poleward and very small, is increased.
The estimation of the salinity effect on the current studies shows that a change in
surface salinity forcing fields by an amount of 0.0817ppt in subarctic area does not have
significant impacts on the results of this study.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/7758 |
| Date | 05 1900 |
| Creators | Wu, Qiuying |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
Page generated in 0.0149 seconds