CLIVAR Tiger Team 4

• Main Authors: Ken Drinkwater, Juergen Alheit, Antonio Bode, Peter Br, David Checkley, Mathieu Rouault, Andreas Schmittner
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Christensen; Antarc*; Antarctica; Northeast Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.638.2560; http://www.clivar.org/sites/default/files/documents/tigerteams/16_TigerTeam4_Upwelling_Version_1_3.pdf

Upwelling regions of the oceans are the most productive fisheries areas in the world. For example, approximately 7 % of primary production and 20 % of the total global marine fish catches come from eastern boundary upwelling areas alone but occupy <2 % of the total ocean area (Pauly and Christensen, 1995). These include the Humboldt Current off Peru, the California Current, the Northeast Atlantic off the Iberian Peninsula and NW Africa, and the Benguela Current off southern Africa. They are examples of coastal upwelling driven by wind-induced Ekman divergence against a coastline. Upwelling favourable winds force warmer near surface waters offshore to be replaced by colder, lower oxygenated, high nutrient rich waters. This often results in high primary production and sometimes in hypoxia (Chan et al., 2008). Wind-induced upwelling also occurs around Antarctica owing to the mean anticyclonic winds. However, many other types of upwelling systems exist. Upwelling occurs in western boundary currents, e.g. the Kuroshio, the Gulf Stream, the Agulhas Current, and the East Australian Current. These currents, being in approximate geostrophic balance, have a strong tilt in the density surfaces, and subsequently the thermocline, upwards towards the shelf. Velocity changes in the currents lead to variability in the thermocline depth and can