Prof. Yongsong Huang Department of Earth, Environmental and Planetary Sciences Brown University
The alkenones and genetic profiles of the Greenland haptophyte were first described in a set of oligosaline lakes in the southwestern Greenland (D'Andrea and Huang, 2005, D'Andrea et al., 2006). However, it is not until a major improvement in chromatographic separation methodology (Longo et al., 2013) that a unique feature in alkenone distribution in this alga is discovered: the tri-unsaturated alkenones in this alga all contain an isomer that is not produced by other haptophyte species. So far this alga has not been isolated from the environment, hence the temperature calibration of alkenones has to rely on in-situ water column samples. D'Andrea et al (2011) calibration for the Greenland haptophyte required making major assumptions and is highly tentative. Our recent discovery of the Greenland haptophyte in more than 70 % of the surveyed freshwater lakes in northern Alaska provide unprecedented opportunity to greatly refine the temperature calibration, and understand conditions that promote the growth of this alga. I will describe our systematic efforts to obtain solid temperature calibration for the Greenland haptophyte from Alaskan lakes and statistic analysis to reveal how environmental parameters in lakes affect the occurrence and abundance of this alga. I will also describe the full structure elucidation for the alkenone isomers (Dillon et al., 2015). Two case studies for paleotemperature reconstruction will be presented: one in Southwestern Greenland over the Holocene and another Northern Alaska for the last 17 kyr. We show alkenones provide invaluable quantitative temperature reconstructions for the late spring/early summer season. In the case of Greenland, the data provide a new explanation for people's migration (including disappearance of the Vikings). In the case of northern Alaska, the data provide new insight to the sea ice changes in the Arctic Sea.