Length Scales of Interannual Sea Level Variations along the Pacific Margin

David Roach TOGA Sea Level Center, Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii

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Gary T. Mitchum TOGA Sea Level Center, Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii

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Klaus Wyrtki TOGA Sea Level Center, Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii

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Abstract

Correlations of monthly mean sea level variations along the Pacific Ocean margin are used to define length scales. In the northeast quadrant a minimum length scale at about 38°N separates two distinct regimes of longer length scale. This transition corresponds to a change from a regime north of 38° that is dominated by local atmospheric forcing to a regime south of 38° that is dominated by remote forcing. In the northwest quadrant a transition occurs near 35°N near the point of the separation of the Kuroshio. A transition at about 30°S in the southwest quadrant is associated with the southernmost extent of the Great Barrier Reef off the coast of Australia. In the southeast quadrant, a transition is observed at 18°S that may be due to a sharp change in the direction of the South American coastline. In general. tropical length scale values of 800 to 3100 km are separated from midlatitude values of 700 to 1300 km by a narrow region in which length scales are as short as 250 km. These results suggest the need for latitude-dependent criteria for the spacing of tide gauges in a global oceanographic sea level system.

Abstract

Correlations of monthly mean sea level variations along the Pacific Ocean margin are used to define length scales. In the northeast quadrant a minimum length scale at about 38°N separates two distinct regimes of longer length scale. This transition corresponds to a change from a regime north of 38° that is dominated by local atmospheric forcing to a regime south of 38° that is dominated by remote forcing. In the northwest quadrant a transition occurs near 35°N near the point of the separation of the Kuroshio. A transition at about 30°S in the southwest quadrant is associated with the southernmost extent of the Great Barrier Reef off the coast of Australia. In the southeast quadrant, a transition is observed at 18°S that may be due to a sharp change in the direction of the South American coastline. In general. tropical length scale values of 800 to 3100 km are separated from midlatitude values of 700 to 1300 km by a narrow region in which length scales are as short as 250 km. These results suggest the need for latitude-dependent criteria for the spacing of tide gauges in a global oceanographic sea level system.

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