Seminar

The physical, biological and biogeochemical oceanography of the North Atlantic is highly sensitive to ongoing climate disruption. North Atlantic convection, a key component of the global thermohaline circulation, is projected to decline due to increased freshwater fluxes characteristic of the twenty-first century. Because this circulation pattern irrigates the region with nitrate, a critical limiting nutrient, such physical disruptions may also suppress biological primary productivity, thereby potentially impacting marine ecosystems and socioeconomically important fisheries. To better constrain these dynamics, I elucidated the response of nutrient advection to past and present climate change along the subpolar Labrador Shelf region using nitrogen isotopes measured from a six-hundred-year-old crustose coralline alga skeleton. However, the long-term (multi-centennial) response of North Atlantic convection to prolonged freshening is not well understood. The late-Pleistocene marine isotope stage (MIS) 11 interglacial period (424 – 374 ka) offers a unique window to assess possible near-future oceanographic change, as this period was anomalously long, warm and characterized by extensive freshening in the high-latitude North Atlantic. Using a variety of paleo-proxy evidence, I argue that the Nordic Seas in the polar north-eastern Atlantic became critical to driving convection during this interval, which may be relevant to the contemporary ocean.

Additional information: Mr. John M. DOHERTY, jdoherty@connect.hku.hk