Thursday 17 June 2010, 11:30 AM (AAD Theatrette)

Takeshi Tamura

Previous Affiliation: Institute of Low Temperature Science, Hokkaido University

Global mapping of sea ice production

The sinking of dense water in the polar regions drives the global thermohaline circulation, leading to heat and material exchange between the atmosphere and deep ocean. Active sea-ice production in coastal polynyas causes dense water formation, finally leading to Antarctic Bottom Water (AABW) formation in the Southern Ocean, and thus polynya monitoring including an estimate of thin ice thickness is essential. This study presents the first mapping of sea ice production in the both polar oceans, based on heat-flux calculation with ice thickness data derived from satellite data. The Cape Darnley polynya in East Antarctica is found to be the second highest production area in the Southern Ocean, suggesting a possible new dense water or AABW formation area. Motivated by this result, the Japanese program of the International Polar Year plans to focus on this polynya and is now deploying ADCPs and Ice Profiling Sonars. The mapping also provides the basic information for the surface heat- and salt-flux conditions in the ice-covered sea, which have not been well understood, and will be useful for validating and providing boundary conditions for coupled atmosphere-ice-ocean models.

BIO: B.Sc., Hokkaido University, Japan, Mar 2001 (Department of Earth Sciences, Faculty of Science); M.Sc., Hokkaido University, Japan, Mar 2003 (Graduate School of Environmental Earth Science); Ph.D., Hokkaido University, Japan, Mar 2007 (Graduate School of Environmental Earth Science); Postdoctoral Researcher, Institute of Low Temperature Science, Hokkaido University, Japan, Apr 2007 - Feb 2010 (Core Research for Evolutional Science and Technology of Japan Science and Technology Agency).

Takeshi has been working under the theme of "Detection of Antarctic coastal polynyas from passive microwave data and estimation of sea ice production there". This study estimates sea ice thickness in the thin ice region (coastal polynyas) in the Southern Ocean from satellite data (i.e., SSM/I, AVHRR, MODIS), and maps ice production in Antarctic coastal polynyas using the heat flux calculation and a sea ice thickness algorithm (collaboration with Drs. Don Cavalieri and Thorsten Markus of NASA GSFC). For the validation of satellite data with in-situ observation data, he took part in the Australian-led international experiment ARISE in September-October 2003. He joined the similar Australian-led international experiment SIPEX again in September-October 2007, to validate satellite microwave data with sea ice thickness data acquired in-situ and from a heli-borne portable passive microwave radiometer.