120 years of sea-ice cover on the Northeast Greenland continental shelf: a biomarker and observational record comparison

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Abstract. This study reconstructs recent changes (ca. 120 years) in sea-ice cover, using biomarkers (IP25 and phytoplankton sterols) from three sediment cores located in a transect across Belgica Trough, on the Northeast Greenland continental shelf. These results are evaluated using instrumental and historical data from the same region and time period. Over the entire 120-year study period, IP25 concentrations are highest at the inner shelf (site 90R) and decrease towards the mid-shelf (site 109R), with lowest values found at the outer shelf (site 134R). The PIP25 index yields the highest sea-ice cover at sites 109R and 90R and lowest at 134R, in agreement with observational records. A decline in sea-ice cover, identified visually and using change point analysis, occurs from 1971 in the observational sea-ice data at sites 90R and 109R. A change in sea-ice cover occurs in 1984 at site 134R. Sea-ice cover in these years aligns with an increase in sterol biomarkers and IP25 at all three sites and decline in the PIP25 index at sites 90R and 134R. The outcomes of this study support the reliability of biomarkers for sea-ice reconstructions in this region.

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