Tropical Instability Wave interactions within the Galápagos Archipelago
William
V
Sweet, North Carolina State University, wvsweet@ncsu.edu
John
M
Morrison, University of North Carolina Wilmington, morrisonj@uncw.edu
(Presenting)
Dan
Kamykowski, North Carolina State University, dan_kamykowski@ncsu.edu
Blake
A
Schaeffer, US EPA Gulf Ecology Division, blakeschaeffer@gmail.com
Stuart
Banks, Charles Darwin Research Station, sbanks@fcdarwin.org.ec
In the boreal fall of 2005, the effects of tropical instability waves (TIW) appear as oscillations within the sea surface temperature (SST), meridional current (Vy), and thermocline (20°C) in the eastern equatorial Pacific. The period of the Vy oscillation between June 2005 and March 2006 along the equator is ~17.1 days at 140°W, ~19.4 days at 110°W, and ~15.3 days for oscillations in the thermocline/SST at 95°W. The oscillations are most noticeable from September 2005 - February 2006. Subsurface (5 m) temperature and water level data from four moorings within the Galápagos Archipelago resolve a 14 to 15-day TIW period between June and December 2005. The effects of the TIW are most noticeable in the archipelago during September and October 2005. Upwelling speeds of ~5.5 m day-1 occurred within the central archipelago from the TIW that decreased surface temperatures ~7°C in a week&rsquos time. Large meridional oscillations of the equatorial front (EF) by the TIW are observed at all locations, except between ~95°W and the western side of Isabela, where the changes of the thermocline (water level/dynamic height) are in phase with those of the SST. A significant biological response to the TIW is observed throughout the archipelago. Coincident within coldest temperatures from three successive TIW upwelling events (1.5-month period), the chlorophyll a (Chl a) increased across the archipelago by ~25 to 40% above its three-year mean for 2004 - 2006. The much larger Chl a levels along/within the archipelago as compared to 95°, 110°, and 140°W implicates that the island platform itself further iron-enriched the upwelling waters.
This project was supported by NASA&rsquos Biodiversity and Ecological Forecasting grant NNG04GL98G, Counterpart US-AID No. 518-A-00-03-00152-00 to the Charles Darwin Research Station and UK Darwin Initiative Project No. 14-048.
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