FEATURE THE 1976-77 CLIMATE PACIFIC OCEAN SHIFT OF THE
Understanding how climate varies in time is a central issue of climate research. Of particular in-terest are climate variations which occur within the human lifespan, say over 5- to 100-y time scales. Climate changes might occur as a gradual drift to a new state, a series of long-term swings, or a s...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.545.1122 http://horizon.ucsd.edu/miller/download/climateshift/climate_shift.pdf |
| Summary: | Understanding how climate varies in time is a central issue of climate research. Of particular in-terest are climate variations which occur within the human lifespan, say over 5- to 100-y time scales. Climate changes might occur as a gradual drift to a new state, a series of long-term swings, or a sequence of abrupt steps. The climate record over the last 100 years or so exhibits ample evi-dence for all these types of variations (Jones et al., 1986), but we have little understanding of what causes and controls these regime changes (Karl, 1988; Wunsch, 1992). Though many of these vari-ations in climate are certainly natural, some com-ponents could be associated with increased con-centrations of greenhouse gases or other anthropogenic effects. To advance our understand-ing of mankind's potential influence on climate, the study of various natural climate variations is of paramount importance. During the 1976-77 winter season, the atmos-phere-ocean climate system over the North Pacific Ocean was observed to shift its basic state abruptly (e.g., Graham, 1994). The Aleutian Low deepened (Fig. la) causing the storm tracks to shift south-ward and to increase storm intensity. Downstream, over the continent of North America, warmer tem-peratures occurred in the northwest (Folland and Parker, 1990), decreased storminess was observed in the southeastern U.S. (Trenberth and Hurrell, 1993), and diminished precipitation and streamflow in the western U.S. (Cayan and Peterson, 1989). In the ocean, sea surface temperature (SST) cooled in the central Pacific and warmed off the coast of western North America (Fig. l c). These major changes in the physical climate were accompanied by equally impressive changes in the biota of the Pacific basin (Venrick et al., 1987; Polovina et al., 1994). This remarkable climate transition was illus-trated by Ebbesmeyer et al. (1991) in a composite |
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