Biomarker characterization of the North Water Polynya, Baffin Bay:implications for local sea ice and temperature proxies

The North Water Polynya (NOW, Inuktitut: Sarvarjuaq; Kalaallisut:Pikialasorsuaq), Baffin Bay, is the largest polynya and one of the most productive regionsin the Arctic. This area of thin to absent sea ice is a critical moisturesource for local ice sheet sustenance and, coupled with the inflow ofnutrient-rich Arctic Surface Water, supports a diverse community of Arcticfauna and indigenous people. Although paleoceanographic records provideimportant insight into the NOW's past behavior, it is critical that webetter understand the modern functionality of paleoceanographic proxies. Inthis study, we analyzed lipid biomarkers, including algal highly branchedisoprenoids and sterols for sea ice extent and pelagic productivity andarchaeal glycerol dibiphytanyl glycerol tetraethers (GDGTs) for ocean temperature, in a set of modern surface sedimentsamples from within and around the NOW. In conjunction with previouslypublished datasets, our results show that all highly branched isoprenoidsexhibit strong correlations with each other and not with sterols, whichsuggests a spring or autumn sea ice diatom source for all highly branched isoprenoids (HBIs) rather than acombination of sea ice and open-water diatoms as seen elsewhere in theArctic. Sterols are also highly concentrated in the NOW and exhibitstatistically higher concentrations here compared to sites south of the NOW,consistent with the order of magnitude higher primary productivity observedwithin the NOW relative to surrounding waters in spring and summer months.Finally, our local temperature calibrations for GDGTs and OH-GDGTs reducethe uncertainty present in global temperature calibrations but alsoidentify some additional variables that may be important in controllingtheir local distribution, such as nitrate availability and dissolved oxygen.Collectively, our analyses provide new insight into the utility of theselipid biomarker proxies in high-latitude settings and will help provide arefined perspective on the past development of the NOW with theirapplication in downcore reconstructions.

Automated summary

The North Water Polynya (NOW) in Baffin Bay is a highly productive region and a crucial moisture source for local ice sheet sustenance. This study analyzed lipid biomarkers in modern surface sediment samples to better understand the functionality of paleoceanographic proxies. The results show strong correlations between highly branched isoprenoids and a higher concentration of sterols in the NOW, providing new insight into past development and downcore reconstructions.