Laminated west Greenland lake sediments as unique climatic and biogeochemical archives

Brown University, Providence RI

Investigators

Abstract

ABSTRACT Huang OPP-0520718 Ice cores from the summit of the Greenland ice sheet have provided high-resolution Holocene temperature and precipitation records. However, Greenland is characterized by large spatial variations in climate and its controlling factors. Notably, summit temperature shows little correlation, whereas southwest Greenland coastal temperature shows strong negative correlation with the North Atlantic Oscillation (NAO). The Principal Investigator will construct new high resolution decadal-scale records of temperature and effective precipitation for the past 8000 years from the laminated sediments of three closed basin lakes near the head of the Sondre Stromfjord. The study is an outgrowth of recent research that found unprecedented abundances of long chain alkenones in the sediments of these lakes. The molecular and D/H ratios of alkenones will allow quantitative reconstruction of temperature and effective precipitation, while biomarker abundances and isotope ratios will provide additional assessment of lake biogeochemical changes. Lacustrine alkenone producers have remained elusive to biogeochemists for over 20 years. These study sites offer a unique opportunity to study the identity, diversity and evolution of alkenone producers in lakes using genetic sequencing and laboratory culturing, building upon our initial results indicating excellent preservation of haptophyte DNA in the sediments. Intellectual merits: This study will provide new insights into the Holocene variability of climate, NAO and lake biogeochemistry in southern west Greenland. Identification of the lacustrine alkenone producers will allow accurate culture calibration of alkenone unsaturation ratios to environmental variables. Comparative sequence analysis of 18S rDNA preserved in sediments will establish the diversity and evolution of haptophyte algae in the Greenland lakes. Organic geochemical studies have been reported in a number of Antarctic lakes. However, despite the presence of >20,000 lakes in the ice-free margins of Greenland, our ABSTRACT Huang OPP-0520718 Ice cores from the summit of the Greenland ice sheet have provided high-resolution Holocene temperature and precipitation records. However, Greenland is characterized by large spatial variations in climate and its controlling factors. Notably, summit temperature shows little correlation, whereas southwest Greenland coastal temperature shows strong negative correlation with the North Atlantic Oscillation (NAO). The Principal Investigator will construct new high resolution decadal-scale records of temperature and effective precipitation for the past 8000 years from the laminated sediments of three closed basin lakes near the head of the Sondre Stromfjord. The study is an outgrowth of recent research that found unprecedented abundances of long chain alkenones in the sediments of these lakes. The molecular and D/H ratios of alkenones will allow quantitative reconstruction of temperature and effective precipitation, while biomarker abundances and isotope ratios will provide additional assessment of lake biogeochemical changes. Lacustrine alkenone producers have remained elusive to biogeochemists for over 20 years. These study sites offer a unique opportunity to study the identity, diversity and evolution of alkenone producers in lakes using genetic sequencing and laboratory culturing, building upon our initial results indicating excellent preservation of haptophyte DNA in the sediments. Intellectual merits: This study will provide new insights into the Holocene variability of climate, NAO and lake biogeochemistry in southern west Greenland. Identification of the lacustrine alkenone producers will allow accurate culture calibration of alkenone unsaturation ratios to environmental variables. Comparative sequence analysis of 18S rDNA preserved in sediments will establish the diversity and evolution of haptophyte algae in the Greenland lakes. Organic geochemical studies have been reported in a number of Antarctic lakes.