Preprints
https://doi.org/10.5194/bg-2021-177
https://doi.org/10.5194/bg-2021-177

  12 Jul 2021

12 Jul 2021

Review status: this discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The manuscript was not accepted for further review after discussion.

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

David J. Harning1, Brooke Holman1, Lineke Woelders1, Anne E. Jennings1, and Julio Sepúlveda1,2 David J. Harning et al.
  • 1Institute of Arctic and Alpine Research, University of Colorado, Boulder, USA
  • 2Department of Geological Sciences, University of Colorado, Boulder, USA

Abstract. The North Water Polynya (NOW, Greenlandic Inuit: Pikialasorsuaq), Baffin Bay, is the largest polynya and one of the most productive regions in the Arctic. This area of thin to absent sea ice is a critical moisture source for local ice sheet sustenance and coupled with the inflow of nutrient-rich Arctic Surface Water, supports a diverse community of Arctic fauna and indigenous people. Although paleoceanographic records can provide critical insight into the NOW’s past behavior, it is critical that we fully understand the modern functionality of the paleoceanographic proxies beforehand. In this study, we analyzed lipid biomarkers, including algal highly-branched isoprenoids and sterols for sea ice extent and pelagic productivity, and algal alkenones and archaeal GDGTs for ocean temperature, in a suite of modern surface sediment samples from within and around the NOW. Our data show that all highly-branched isoprenoids exhibit strong correlations with each other and show highest concentrations within the NOW, which suggests a spring/autumn sea ice diatom source rather than a combination of sea ice and open water diatoms as seen elsewhere in the Arctic. Sterols are also highly concentrated in the NOW and exhibit an order of magnitude higher concentration here compared to sites south of the NOW, consistent with the order of magnitude higher primary productivity observed within the NOW relative to surrounding waters in spring/summer months. Finally, our temperature calibrations for alkenones, GDGTs and OH-GDGTs reduce the uncertainty present in global temperature calibrations, but also identify some additional variables that may be important in controlling their local distribution, such as salinity, nutrients, and dissolved oxygen. Collectively, our datasets provide new insight into the utility of these lipid biomarker proxies in high-latitude settings and will help provide a refined perspective on the Holocene development of the NOW with their application in downcore reconstructions.

David J. Harning et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-177', Anonymous Referee #1, 29 Jul 2021
    • AC1: 'Reply on RC1', David Harning, 19 Sep 2021
  • RC2: 'Comment on bg-2021-177', Ruediger Stein, 18 Aug 2021
    • AC2: 'Reply on RC2', David Harning, 19 Sep 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-177', Anonymous Referee #1, 29 Jul 2021
    • AC1: 'Reply on RC1', David Harning, 19 Sep 2021
  • RC2: 'Comment on bg-2021-177', Ruediger Stein, 18 Aug 2021
    • AC2: 'Reply on RC2', David Harning, 19 Sep 2021

David J. Harning et al.

David J. Harning et al.

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Short summary
In order to better reconstruct the geologic history of the North Water Polynya, we provide modern validations and calibrations of lipid biomarker proxies in Baffin Bay. We find that sterols, rather than HBIs, most accurately capture the current extent of the North Water Polynya and will be a valuable tool to reconstruct its past presence/absence. Our local temperature calibrations for alkenones, GDGTs and OH-GDGTs reduce the uncertainty present in global temperature calibrations.
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