Assessing Methanesulfonate as a Proxy for Sea Ice Concentration Using Firn Cores from the Disko Bay Region of Greenland
Abstract
The Jakobshavn Glacier, responsible for draining upwards of 7% of the Greenland Ice Sheet (GIS) into Disko Bay, has experienced terminal retreat in recent decades. High sea ice concentrations have been heavily implicated in the blocking of glacier calving, thereby reducing glacial retreat. However, the satellite imagery used to evaluate levels of sea ice only spans the past few decades, thus establishing the necessity for a valid proxy to generate records father into the past. Methanesulfonate (MSA) is an oxidation product of dimethyl sulfide (DMS), a chemical released by phytoplankton. As phytoplankton population increases with decreased sea ice concentration, MSA concentrations should shift directly with the phytoplankton population and inversely with sea ice concentration.The objective of this study was to evaluate MSA as a natural proxy for sea ice variability.Two meters of firn core were drilled from an ice cap on the Nuussuaq Peninsula, near Disko Bay in April 2014. The core was processed into 3 cm resolution samples for measurement of oxygen isotope ratios by cavity ring down spectroscopy and MSA concentrations by ion chromatography. Sea Ice concentrations at three locations around Disko Bay were calculated using IDRISI software (a GIS) and satellite imagery. Peaks in the oxygen isotope ratio, which has stable seasonal variation with maximum levels in warmer months, were correlated with the likewise seasonal peaks in the percent of the grid uncovered by sea ice (Figure 1). With these corresponding peaks, Taylor series approximation allowed each sample depth to be dated. We subsequently compared MSA concentrations to sea ice concentrations at known dates for three different potential source areas around Disko Bay within 25km by 25km grids. In the grid below Disko Island, peaks in MSA and the inverse of sea ice concentration occurred simultaneously (Figure 2, r=0.4). The parallel peaks in MSA, oxygen isotope and inverse sea ice concentration indicate the potential of MSA as a proxy for sea ice concentration. With the early validation of MSA as a proxy for sea ice, MSA concentrations in older ice cores may be used to understand the effects of sea ice variability on past glacial retreat and subsequently to inform predictions about the future.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMED41A0821T
- Keywords:
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- 0805 Elementary and secondary education;
- EDUCATIONDE: 0825 Teaching methods;
- EDUCATIONDE: 0850 Geoscience education research;
- EDUCATIONDE: 0855 Diversity;
- EDUCATION