Matt Osman is currently a Ph.D. candidate at the Massachusetts Institute of Technology - Woods Hole Oceanographic Institution Joint Program. His research focuses on reconstructing changes in North Atlantic sea-surface variability over recent decades to millennia using high-resolution ice core records from Greenland. Matt is in residence at the Bjerknes Centre on an Ocean Outlook Fellowship for the remainder of Spring 2018, working in collaboration with the ERC-funded ice2ice project.
Marine phytoplankton account for nearly 50% of primary production worldwide, and thus play a critical role in modulating marine-based food webs, fishery yields, and the global drawdown of atmospheric CO2. Yet, despite this importance, little is known about the long-term response of planktonic stocks to climatic forcing. Near-continuous, satellite-based observations of phytoplankton abundance extend back only as far as 1997 (though intermittently to 1979). This observational-paucity requires prior inferences to be drawn from spatiotemporally sparse sources, including ship-based ocean color observations (c. early 20th century to present), or marine proxy records.
In this talk, I present new, annual-scale and spatially-integrated insights into marine-productivity trends occurring across the subarctic Atlantic – one of the most seasonally productive ocean basins in the world – detailing the last ~two and a half centuries. Using a unique signal of planktonic-derived organic aerosol commonly identified across twelve Greenlandic ice core sites, I provide evidence suggesting that recent, satellite-inferred increases in subarctic Atlantic planktonic biomass may be superimposed upon a much longer, multicentury productivity decline. Potential drivers, and implications, of this multicentury decline are hence discussed in the context of i) observed subarctic Atlantic ocean-atmosphere feedbacks (e.g., the North Atlantic Oscillation and Subpolar Gyre), ii) the congruent onset of 19th century Atlantic surface warming, and iii) the purported long-term decline in the vigor of North Atlantic thermohaline overturning.
Arranged date for the seminar talk: Mar 19, 2018