The annual CO2 flux into the ocean north of 14 degN in the Pacific is about equal to the annual flux to the atmosphere from the Equatorial Pacific (14 degN to 14 degS). The strongest region of CO2 uptake in the north Pacific is at the subtropical subarctic front. Although thermodynamic processes primarily control the air-sea CO2 flux in the subtropics, biological and physical mechanisms are much more important at the front and in the subarctic Pacific. Based on current understanding, it is uncertain whether alterations to these physical and biological processes in response to climate change could transform the north Pacific into a stronger source or even into a sink for anthropogenic CO2.
In this research, PIs from the University of Washington and Oregon State University, in close collaboration with scientists from NOAA's Pacific Marine Ecosystems Laboratory, will conduct field studies combined with satellite observations and a modeling investigation to identify the mechanisms controlling the air-sea CO2 flux at the subtropical subarctic front and in the eastern basin of the subarctic Pacific. The field studies comprise three separate components: (1) measurement of pCO2 and oxygen isotope tracers of biological productivity (delta17O, O2/Ar) using a Volunteer Observation Ship (VOS) that crosses the Pacific every other month; (2) determination of carbon fluxes and depth distributions not possible from a VOS using a research cruise between Hawaii and Seattle, and (3) in situ, continuous measurement of T, S, O2, chlorophyll, pCO2 and pH on a surface mooring in the eastern subarctic Pacific at Ocean Station P while simultaneously measuring the four dimensional distribution of T, S, and O2 using a Seaglider survey of the area. These autonomous measurements are focused on identifying the role of intermittency in the biological pump. The field observations will be placed in context by a study of satellite products that identify the role of intermittent forcing (e.g. sea-surface height, atmospheric dust levels) and subsequent productivity events (e.g. ocean color, coccolithophorid blooms). A circulation model of the north Pacific that includes modules for the biological ecosystem and the carbonate chemistry will be combined with the field and satellite data to help distinguish the importance of physical and biological processes in controlling the pCO2 of surface waters at the frontal region.
The most obvious broader impact is the participation of 10 - 15 undergraduate and graduate students on a research expedition between Hawaii and Seattle as part of a course for students of Oceanography at the University of Washington. This research will also support two and one half graduate students who will use the data derived here to complete their Ph.D. research. A greater understanding of carbon cycling in this critically important regime will provide societal benefits.
