Joint Seminar: Measurements of air-sea gas exchange in the coastal and open ocean

In coastal waters, where productive but fragile ecosystems are commonly found, O2 is often depleted in subsurface waters and is therefore of primary concern, while in the global ocean especially the uptake of greenhouse gases like CO2 is of interest. Despite its profound and pervasive influence, air-sea gas exchange remains a poorly quantified and characterized process. Gas exchange mechanisms include the creation, entrainment, and subduction of these bubbles by surface waves, diffusive gas exchange, and biogeochemical processes. In estuaries, tidal fronts are an extreme but widespread phenomena that contribute to the gas exchange. Within such fronts, gas bubbles can be subducted to depths of > 150m, where hydrostatic pressure forces them into dissolution. It has been suggested that this process may
contribute significantly to the aeration of intermediate water. Tidal fronts can occur in conjunction with hydraulically driven plunging currents that subduct aerated water to intermediate depths. These processes deserve therefore special attention, especially in highly productive coastal environments where oxygen depletion in subsurface waters may cause environmental and economic concerns. Gas exchange mechanisms can be disentangled by measuring the time varying concentrations of dissolved inert gases in response to their “forcing”. Since the suite of noble gases span an order of magnitude range of physical characteristics – in particular solubility and molecular diffusivity – the bubble entrainment exhibits distinct responses that allow a quantitative estimate of the contribution of tidal fronts to the aeration of water. Furthermore, the use of the non-reactive noble gases allows for a separation of the physical from the biogeochemical gas exchange processes. In the talk, dissolved gas measurements from the Saguenay Fjord, QC, Canada, and the Bermuda Testbed Mooring (BTM) will be presented.

Date

13.08.2008

Time

15:15 h

Place

Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg

Speaker

Burkard Baschek, University of California at Los Angeles

Organizers


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