[PAOCQ] Hilary Palevsky (BC)

“Interconnected biological and physical controls on the ocean’s biological carbon pump”

Photosynthetic fixation of organic carbon and export of a fraction of that carbon from the surface to the deep ocean – the biological pump – plays a key role in enabling the ocean to absorb carbon dioxide from the atmosphere. However, in regions that experience deep winter mixing, much of the organic carbon exported from the seasonally-stratified surface ocean is subsequently respired within the thermocline and ventilated back to the atmosphere during winter rather than being sequestered on annual or longer time scales. In this talk, I will show how physical and biogeochemical sensors deployed on moorings and gliders at the Ocean Observatories Initiative’s Irminger Sea Array since 2014 provide insights into these complex dynamics. This site features some of the deepest winter convection found anywhere in the global ocean, with maximum annual winter mixing ranging from 400-1400m. This deep winter mixing both reduces carbon sequestration at depth by ventilating 65-100% of the carbon respired within the seasonal thermocline, but also promotes carbon flux to depth by small particles that are detrained when the mixed layer shoals in spring. In addition to the small particle carbon pool transported to depth by mixing, sub-daily optical backscatter profiles show annual pulses of large fast-sinking particles that penetrate to below 2000m, driving additional carbon sequestration. I will discuss the implications of this work for our understanding of the biological pump’s role in driving ocean carbon uptake, as well as the role of sustained time-series observations in advancing our understanding of ocean carbon cycling.

PAOC Colloquium —

Interdisciplinary seminar series that brings together the whole PAOC (Program in Atmospheres, Oceans, and Climate) community. Seminar topics include all research concerning the physics, chemistry, and biology of the atmospheres, oceans and climate, as well as talks about societal impacts of climatic processes.

Contact: paoc-colloquium-comm@mit.edu