Regional Climate: Current Research
Coastal Upwelling: Past, Present and Future
- Todd Mitchell, UW Climate Impacts Group
- Nathan Mantua, UW Climate Impacts Group
- Eric Salathé, UW Climate Impacts Group
The failure of the 2005 upwelling season along the Oregon and Washington coast focused interest in understanding how large-scale atmospheric climate variability influences upwelling along the west coast of the U.S. and in coastal upwelling regions around the globe. In support of a NOAA-led effort to understand the 2005 upwelling episode, an historical upwelling index was developed from sea-level pressure records, and the index used to document the regional scale of the phenomenon.
Studies of the response of low spatial-resolution atmospheric models to increased CO2 concentrations suggest that changes in sea-level pressure would affect coastal upwelling, and analyses of ocean-atmosphere models, as part of the IPCC assessment, have suggested that a slowdown of the tropical circulation has already occurred and is a part of the global warming signature. The slowing down of the circulation is manifested by a weakening of the subtropical highs in the Pacific (associated with the Southern Oscillation), and this weakening might be expected to weaken the coastal upwelling.
We are analyzing satellite-derived and in situ observations, and outputs from global IPCC models, as well as dynamically downscaled IPCC scenarios, to document changes in the large-scale atmospheric circulation during the upwelling seasons (May-June-July for the Northern Hemisphere, and December-January-February for the Southern Hemisphere). COADS surface windstress fields have been analyzed for dominant patterns of coastal and open ocean upwelling, and a 25 year record of satellite-derived windstress fields are currently being analyzed. Future projections from 100-year regional climate model simulations forced with outputs from the global NCAR-CCSM3 and the MPI-ECHAM5 models, respectively, will also be compared with coarse resolution projections from other global climate models used in the IPCC’s Fourth Assessment Report.
NOAA Fisheries and Their Environment (FATE)
For more publications on climate impacts on PNW climate, please see CIG Publications.