Year: 2012
Type: article
Abstract: Off the west coast Mexico, in the Eastern Tropical North Pacific, there is a vast layer of water with extremely low oxygen content.This low-oxygen layer, commonly referred to as an oxygen minimum zone (OMZ), has been surveyed numerous times since the 1960s.According to a theory proposed in 1999, a rise in global temperatures will cause the volume of the OMZ to increase, becoming both shallower and deeper in the water column.To determine whether or not there has been a change in the vertical extent of the OMZ in the ETNP, I made oxygen concentration profiles along a transect from San Diego, CA to Manzanillo, MX, and made a cross-sectional profile of oxygen concentrations along 110°W to compare with past studies.The primary data presented in this paper was gathered during R/V Thomas.G. Thompson cruise TN278 which took place 16 March to 23 April 2012.I found that the OMZ is encroaching on coastal areas and has increased in size and intensity over the past forty years.It is important to understand the extent and changes with time of the OMZ, as OMZs have a strong impact on the carbon and nitrogen cycles through carbon sequestration and denitrification.The feedback effects that change these cycles make OMZs important areas to study so that we may better predict future climatic and oceanic conditions.. ABSTRACTOff the west coast Mexico, in the Eastern Tropical North Pacific, there is a vast Oxygen Minimum Zone (OMZ).An analysis of O 2 concentration measurements in the ETNP made in 1972 identified a 600m thick layer of water with almost no detectable oxygen (Cline and Richards 1972).According to a theory proposed in 1999, a rise in global temperatures will cause the volume of the OMZ to increase, becoming both shallower and deeper in the water column (Cannariato and Kennett 1999).The primary data used for this paper was gathered during R/V Thomas.G. Thompson cruise TN278 which took place 16 March to 23 April 2012.To determine whether or not there has been a change in the vertical extent of the OMZ, I collected water samples with Niskin bottles at ten stations along a transect from San Diego, CA to Manzanillo, MX and gathered oxygen concentration data using a CTD sensor while on board the R/V Thomas G. Thompson.Titrations were performed on the water samples using the Winkler method (Winkler 1888) as modified by Carpenter (1965).The results of the titration were used to calibrate the sensor readings, and corrected sensor profiles were compared to observations made during past cruises.It is important to understand the extent and changes with time of the OMZ, as OMZs have a strong impact on the carbon and nitrogen cycles (Devol and Hartnett 2001, Paulmier andRuiz-Pino 2009) through carbon sequestration and denitrification.The feedback effects that changes to these cycles may have makes OMZs important areas to study so that we may better predict future climatic and oceanic conditions.
Author: Erika A. Fee
Institution: University of Washington
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2296086527