Past and Present Coastal Upwelling Along the Western Americas

Abstract

Every year, increasing insolation during spring and summer sets up a broad pattern of equatorward winds along the western shores of North and South America. These winds are responsible for large-scale advection of nutrient-rich waters to the surface and, therefore, the elevated productivity of the California and Peru/Humboldt eastern boundary current systems. Because the Earth’s radiation balance is involved, eastern boundary currents probably responded to past changes in summer insolation and could be sensitive to future changes in greenhouse gas concentrations. The hydrography of the nutrient-like trace element Cd and its incorporation into the geologic record provide a unique way to quantify the sensitivity of coastal upwelling to climate change, using the effect of orbital changes in insolation during the Holocene as a test case.