Collaborative Research: Historic perspectives on climate and biogeography from deep-sea corals in the Drake Passage
Laura F. Robinson & Rhian G. Waller
Polar Oceans are the main sites of deep-water formation and are critical to the exchange of heat and carbon between the deep-ocean and atmosphere. Testing hypotheses that link processes in the Southern Ocean to climate change over millennia is challenging because our knowledge of the biogeochemistry and circulation in the Southern Ocean in the past is limited by scarcity of suitable records. The skeletons of deep sea corals are abundant in the Southern Ocean, and can be dated using U-series techniques making them a useful archive of oceanographic history. By pairing U-series and radiocarbon analyses we can use deep-sea corals to reconstruct the radiocarbon content of seawater in the past. A successful pilot cruise in 2008 demonstrated our ability to collect live and fossil deep-water corals from the Drake Passage and preliminary results prove that fossil individuals date back through the Holocene, deglaciation, last glacial maximum and beyond.
In May 2011 we will follow-up our pilot cruise to collect full depth transects of deep-sea corals crossing the major oceanographic fronts. The direct output of this proposal will include (1) completion of mapping started in 2008, and the first mapping of new areas of the Drake Passage; (2) identifying present and past distributions of deep-sea corals using digital images and collections; and (3) reconstruction of full radiocarbon depth profiles from the last glacial and deglaciation. These full depth profiles will add to samples collected previously and allow us put new constraints on the extent of air-sea gas exchange, polar water-column stratification and the flux of Southern sourced deep water to the rest of the world’s oceans in the past. Data from this cruise will form the first systematic study of constraints and environmental controls on deep-water coral biogeography in this sensitive and understudied region.
Planned sites for the NBP11-03 cruise