Island mass effect in the Marquesas Islands: Time variation

Abstract

Chlorophyll a in the Marquesas islands has been analyzed for the period 1997-2002 as well as simultaneous sea surface height anomaly, sea surface temperature, wind and rainfall. For the first time, the seasonality of phytoplankton blooms is shown around the Marquesas Islands. Clearly, the data show three types of blooms in this area: seasonal blooms, episodic ones, and La Niña (related bloom). Initiation of blooms is due to the island mass effect and has been explained by the dynamic interaction of the circulation and the topography. The island mass effect blooms are strongly correlated with the total (Ekman plus geostrophic) surface current and episodically correlated with the geostrophic current. Strong correlation is also observed with sea surface temperature. Analysis of rainfall data suggests that land drainage can enhance a bloom if the current dispersing the nutrients is sufficiently strong. Copyright 2004 by the American Geophysical Union.