Monthly mean coastal upwelling indices, west coast of South Africa 1981 to 2000 trends and relationships

The Pacific Fisheries Environmental Laboratory (PFEL) Upwelling Index provides continuous proxy time series of coastal ocean processes which are difficult to measure directly and are infrequently available as multiyear time series for the study of surface layer physical and biological ocean dynamics. The PFEL Upwelling Index (UI) is derived from analyzed pressure fields using planetary boundary layer theory and geostrophic wind approximation to derive inferences about momentum transport from the wind to the sea surface layer. The UI values for the period January 1981 through December 2000 are presented for the highly productive upwelling systems off the coast of southwest Africa. These data have been extracted for three sets of nine locations from 15° to 36°S. Large-scale characteristics of these time series include: 1) Highest UI values are in the austral spring and summer; 2) Maximum UI occurs earlier in the year at lower latitudes; 3) South of 33°S, mean UI is negative for short periods during austral winter; 4) Interannual variation is greatest in the north, but south of 33°S there is also a maximum in standard deviation during austral winter; 5) Austral spring and summer UI increases from 36° to 27°S; 6) Variation in UI is dependent on computation point, distance from shore and adjacent land topography; and 7) Radiative atmospheric heating over adjacent desert may enhance UI from 21°S equatorward. The UI for the west coast of southern Africa reflects physical environmental changes expected to influence temporally and spatially coincident ecosystems by indicating nutrient availability in the euphotic zone. Jerrold G. Norton, Frank B. Schwing, Mark H. Pickett, Steven G. Cummings, David M. Husby, Phaedra Green Jessen. "September 2002." System requirements: Adobe Acrobat Reader. Mode of access: World Wide Web. Includes bibliographical references (p. 22-24).