Lipschultz, F. Bermuda Biological Station for Research, Inc., fred@bbsr.eud
Montoya, J. Georgia Institute of Technology, j.montoya@biology.gatech.edu

 
THE OXYGEN MINIMUM ZONE OF THE EASTERN TROPICAL NORTH PACIFIC: HYDROGRAPHY AND NUTRIENTS UNDER THE INFLUENCE OF EL NINO
 
The Oxygen Minimum Zone (OMZ) of the eastern tropical North Pacific (ETNP) is one of three regions of the oceans where denitrification occurs in the water column. As part of a project to measure denitrification and other nitrogen cycle rates, two cruises were conducted in the region during May, 1997 before the El Nino, and again in November 1997 as the El Nino approached its peak. Standard CTD, ADCP and nutrient analyses were made, and oxygen concentrations were determined using the microwinkler technique. Maximum nitrite concentrations were more than twice those measured in the early 1970's although the profiles had similar shape. Significant nitrite only occurred below 2 microgram-atom/liter oxygen with no difference between May and November . The OMZ extended further south and was more pronounced at depth in 1997. During 1997, the oxygen gradient at the surface extent of the OMZ was sharper and deeper in November than in May. The horizontal extent of the OMZ did not extend as far west as is traditionally assumed in regional calculations of denitrification. Given the paucity of data in this region, it is difficult to isolate the confounding influences of seasonal variations, the El Nino or interdecadal differences.
 
Day: Friday, Feb. 5
Time: 11:30 - 11:45am
Location: Sweeney Center
 
Code: CS55FR1130S