BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:The pulse of the Southern Ocean - Kate Hendry\, University of Bris tol DTSTART:20140204T163000Z DTEND:20140204T173000Z UID:TALK49566@talks.cam.ac.uk CONTACT:Alexandra Turchyn DESCRIPTION:The growth of siliceous phytoplankton\, mainly diatoms\, in th e Southern Ocean influences the ocean nutrient inventory on a global scale . The use of dissolved silicon by diatoms and deep circulation combine to trap silicon in the Southern Ocean resulting in high levels of silica pro duction and expansive diatom oozes in Southern Ocean sediments. The analys is of the silicon isotope composition of biogenic silica\, or opal\, and d issolved silicic acid provide insight into the operation of the global mar ine silicon cycle and the role played by the Southern Ocean in nutrient su pply and carbon drawdown\, both in the modern and in the past. Silicon is otope studies of diatoms have provided insight into the history of silica production in surface waters\, while the analysis of spicules from deep se a sponges has defined both the spatial and the temporal variability of sil icic acid concentrations in the water column\; together these – and othe r - proxies reveal variations in the northward flow of Southern Ocean inte rmediate and mode waters and how changes in Southern Ocean productivity al tered their preformed nutrient content. In this talk\, I will present a n ew hypothesis – the “Silicic Acid Ventilation Hypothesis” – to exp lain the geographical variation of opal-based proxy records\, in particula r the contrasting patterns of opal burial change found in the low and high latitudes. By understanding the silicon isotope systematics of opal an d silicic acid in the modern\, opal-based proxies can be used to reconstru ct past changes in the Southern Ocean and so investigate its role in globa l carbon cycling and climate. LOCATION:Harker 1 seminar room\, Department of Earth Sciences END:VEVENT END:VCALENDAR