Remote Sensing of the NE Pacific: Retrospective and Concurrent Time Series Analysis Using Multiple Sensors on Multiple Scales

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PROJECT SUMMARY: A significant number of physical and biological variables covary within and between the boundary currents of the subarctic and subtropical gyres in the NE Pacific Ocean. These (summarized in US GLOBEC Reports 17, 11 and 7) include the strength of the transports, surface temperatures, zooplankton biomass and the catch of commercially important fishes. Time scales range from individual events to interdecadal regime shifts. The mechanisms by which these physical and biological fields covary are unknown, but it is postulated that the same mechanisms involved in interannual variability also affect long term climatic variability. Clarification and quantification of the mechanisms governing interannual variability will therefore help to `model` the biological and physical responses of these economically and ecologically important systems to future climate change. One of the principal strategies for addressing variability across these time and space scales and their potential linkages is to make effective use of historical and presently available multi sensor satellite data sets. The goal of this proposal is to process, archive and analyze environmental data from a number of satellite sensors and other sources in order to characterize and quantify the dominant modes of variability in surface transports, temperature and pigment concentrations in the NE Pacific Ocean. The analyses will cover multiple time/space scales, considering basin scale connections, mesoscale circulation within specific regions of the boundary currents, and small scale, nearshore circulation in two of the regions. In addition to the analysis carried out in this project, these data will be made available over Internet and on CDROM to other investigators. On the basin scale, the project will quantify the exchange between the West Wind Drift (WWD), the Coastal Gulf of Alaska (CGOA) and the California Current System (CCS), testing the often used hypothesis that the covariability in the two boundary currents is due to changes in the location of the WOOD. The alternate large scale hypothesis is that this is not the case that these boundary currents are forced by the large scale wind systems and that these atmospheric systems covary between the basins. Satellite altimeters and scatterometers provide the instruments to test this hypothesis for the first time. Consistently reanalyzed atmospheric model winds allow a test of the wind covariability over a longer period than possible with the satellite data. The largescale modes of transport variability will be quantified using EOF analysis and Canonical Correlat on Analysis. On the mesoscale, within each boundary current, the combination of AVHRR SST and/or satellite ocean color with altimeter data can resolve mesoscale circulation features with scales of 50 100 km or less. AVHRR and ocean color data, with 1 km resolution, will be collected and processed in ongoing fashion for the three years of the project (1998 2000). Historical 1 km AVERR data over the CCS (25Ý 55ÝN) for the period 1981 1997 will also be processed in identical fashion. These data, will allow an examination of the mesoscale circulation (location and seasonality of jets and eddies) around the sites proposed for process studies in Phase II of the US GLOBEC/CoOP study. The direct transport along the boundaries of British Columbia and the Northwest US will also be examined, to provide greater details about the large scale connection between the gyres. Other areas of focus will be: the region around the Columbia River Plume, due to the impact on out migrating Coho salmon; the region west of Prince William Sound, where juvenile salmon encounter the Alaskan Stream; and details of the flow from the coastal ocean along central and southern Oregon into the core of the California Current oflf northern and central California. The analysis will test the hypothesis that much of the interannual variability seen off central California in the CalCOl?I data set comes from the upwelling region off Oregon, rather than from the WOOD. Combination of the satellite data with in situ data collected during monitoring studies (funded by GLOBEC or other sources) will be used to transform the satellite circulation fields into mass, heat and pigment surface transports. Timing of seasoual transitions will be another focus, due to possible mismatches of coastal ocean environmental couditions with salmon out migrations.