Johannessen, S. C.. Dalhousie University, schjohan@is2.dal.ca
Miller, W. C.. Dalhousie University, william.miller@dal.ca
Cullen, J. J.. Dalhousie University, john.cullen@dal.ca

 
PHOTOCHEMISTRY FROM SPACE: INTEGRATING FIELD DATA WITH THEORY
 
Photochemical oxidation could provide an important sink for dissolved organic carbon in the ocean. To quantify this process it is essential to know how much solar radiation, particularly UV radiation (280-400 nm), is absorbed by coloured, dissolved organic matter (CDOM). Algorithms exist to calculate downwelling attenuation of visible radiation using satellite observations of ocean colour. Using a similar approach, we relate in-situ downwelling attenuation coefficients for UV radiation to upwelling radiance measurements at 412, 443 and 555 nm. We compare measurements of downwelling attenuation in three UV channels (323, 338, 380 nm) at 47 stations in the Mid-Atlantic Bight, the Bering Sea and Bedford Basin, Nova Scotia with CDOM spectral absorptivity measurements. Preliminary results show that absorption by CDOM accounts for close to 100% of UV attenuation offshore and decreases to less than 50% in turbid waters like Delaware Bay. We have developed an empirical algorithm to predict UV downwelling attenuation and the proportion due to CDOM from in-situ upwelling radiance measurements, which we hope to extend to remotely sensed data in the future.
 
Day: Tuesday, Feb. 2
Time: 09:45 - 10:00am
Location: Sweeney Center
 
Code: SS43TU0945S