Project: Tracers of Biological Productivity and Gas Exchange

NSF Award Abstract:

OCE-0242139

The export of carbon from the surface of the ocean is one of the processes controlling the partial pressure of carbon dioxide (pCO2) of the atmosphere, which greatly influences the climate of the Earth. Changes in atmospheric pCO2 over glacial time scales are often interpreted as a response to changes in the ocean's biological carbon pump. Models of the carbon pump are limited by our understanding of mechanisms that control it in different areas of the ocean. Satellite color images hold great promise for determining the biological pump globally, but only if the images can be ground truthed by field measurements. To date this calibration has been achieved in only four places in the ocean: the long-term time series locations and parts of the Equator.

In this project, researchers at the University of Washington will develop experimental methods of improving our knowledge of the ocean.s biological carbon pump. The research program is twofold. First they will deploy four oxygen sensors and a GTD on the new mooring at HOT to measure a profile of O2 in the euphotic zone and the surface concentrations of N2. They believe that this will be sufficient to determine the net biological oxygen production. Two methods will be tested for calibrating the oxygen sensors in situ. This research will develop methods to determine the oxygen mass balance (and hence biological carbon pump) on moorings at other locations in the ocean.

The second, and much smaller, aspect of the project builds on the research team's analytical ability to determine N2, Ar and Ne in seawater. They will conduct a field program to study the concentrations of these gases as a function of wind speed on several short cruises in the Drake Passage of the Southern Ocean. The goal is to develop a correlation between bubble flux and wind speed. This knowledge could be used to characterize the bubble process in locations where it is not possible to measure these gases and to improve estimates of the biologically produced oxygen flux from the ocean using climatological surface ocean oxygen concentrations.

Broader impacts of this proposal include the benefits to society that will result from understanding the marine biological pump well enough to incorporate it into ocean-atmosphere models that will be used to predict future climate. The proposal also promotes education of a graduate student who will work on the project.