Seasonal Particle and Carbon Dynamics in the Eastern Bering Sea

• Main Author: Baumann, Matthew S.
• Format: Text
• Language: unknown
• Published: DigitalCommons@URI 2013
• Subjects: Bering Sea; Sea ice
• Online Access: https://digitalcommons.uri.edu/oa_diss/126; https://doi.org/10.23860/diss-baumann-matthew-2013; https://digitalcommons.uri.edu/context/oa_diss/article/1144/viewcontent/Baumann_uri_0186A_10809.pdf

The ocean margins of high-latitude seas, such as the eastern Bering Sea, are recognized as important areas for the enhanced scavenging removal of particle reactive chemicals and for the potential to sequester atmospheric carbon dioxide via photosynthetic conversion to biogenic particles and subsequent downward particle transport to deeper waters. This region is expected to warm in the future, and with the warming will come a reduction in the extent and duration of seasonal sea-ice. This physical process exerts an important control on the timing, location, and magnitude of the spring primary production bloom. Within the context that 2008-2010 are characterized as cold years in the eastern Bering Sea, establishing the mechanistic link between primary production and the seasonal progression in particle export represents a significant challenge because these processes exert a control on organic matter transport from the surface ocean and on the success of economically and culturally important animals. During spring and summer cruises in 2009 and 2010, distributions of 234Th (t1/2 = 24.1 days) in the water column and sediments were measured at ~60 stations over the middle and outer regions of the shelf and at the shelf break. The inventory of excess 234Th (234Th which is not produced in the sediments) in shelf sediments was ~1/3 of the total deficit of 234Th (234Th scavenged by sinking particles) in the overlying water column leading to an average focusing factor of 0.34 ± 0.23. Further, 234Th export from the shelf was determined to ~30% of the total production of this radionuclide by 238U decay based on a 234Th budget. These results, taken together with elevated focusing factors in the off-shelf region, suggest that the shelf sediments and lateral transport of particles from the shelf represent significant sinks for biogenic particles produced over the shelf in the spring and summer. The elevated focusing factors at the shelf break are attributed to enhanced particle flux from blooms of primary production in this ...