Preprints
https://doi.org/10.5194/cp-2021-99
https://doi.org/10.5194/cp-2021-99

  16 Aug 2021

16 Aug 2021

Review status: this preprint is currently under review for the journal CP.

NEEM to EastGRIP Traverse – spatial variability, seasonality, extreme events and trends in common ice core proxies over the past decades

Helle Astrid Kjær1, Patrick Zens1, Samuel Black1,2, Kasper Holst Lund1, Anders Svensson1, and Paul Vallelonga1,3 Helle Astrid Kjær et al.
  • 1Physics for Ice, Climate and Earth Sciences (PICE), Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
  • 2NatureScot, Inverness, IV3 8NW, United Kingdom
  • 3UWA Oceans Institute, University of Western Australia, Crawley, WA, Australia

Abstract. Greenland ice cores provide information about past climate. However, the number of firn and ice cores from Greenland are limited and thus the spatial variability of the chemical impurities used as proxies is largely unconstrained. Furthermore, few impurity records covering the past two decades exist from Greenland. We have by means of Continuous Flow analysis investigated 6 shallow firn cores obtained in Northern Greenland as part of the NEEM to EastGRIP traverse in 2015. The oldest reach back to 1966.

The annual mean and quartiles of the insoluble dust, ammonium, and calcium concentrations in the 6 firn cores spanning a distance of 426 km overlap, and also the seasonal cycles have similar peaks in timing and magnitude across sites. Peroxide (H2O2) is accumulation dependent and varies from site to site and conductivity, likely influenced by sea salts, also vary spatially.

The temporal variability of the records is further assessed. We find no evidence for increases in total dust concentration, but find an increase in the large dust particle fluxes that we contribute to an activation of Greenland local sources in the recent years (1998–2015). We observe the expected acid and conductivity increase in the mid 70’s as a result of anthropogenic contamination and the following decrease due to mitigation. After detrending using the five year average the conductivity and acid records several volcanic horizons were identified and associated with Icelandic eruptions and volcanic eruptions in the Barents sea region.

By creating a composite based on excess ammonium compared to the five year running average, we obtain a robust forest fire proxy associated primarily with Canadian forest fires (R = 0.51). We also note that the peak ammonium in the individual firn cores appear more scattered between cores than the peak volcanic layers, suggesting that the forest fire signal is more dispersed in the atmosphere than the acid from volcanic eruptions.

Helle Astrid Kjær et al.

Status: open (until 22 Oct 2021)

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  • RC1: 'Comment on cp-2021-99', Anonymous Referee #1, 10 Sep 2021 reply

Helle Astrid Kjær et al.

Helle Astrid Kjær et al.

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Short summary
Six shallow cores from Northern Greenland spanning a distance of 426 km was retrieved during a traverse in 2015. In them we observe an increase in the large dust particle fluxes that we contribute to an activation of Greenland local sources in the recent years (1998–2015). Identify several recent acid horizons associated with Icelandic eruptions and volcanic eruptions in the Barents sea region and obtain a robust forest fire proxy associated primarily with Canadian forest fires.