Articles | Volume 13, issue 2
Clim. Past, 13, 171–184, 2017

Special issue: International Partnerships in Ice Core Sciences (IPICS) Second...

Clim. Past, 13, 171–184, 2017

Research article 27 Feb 2017

Research article | 27 Feb 2017

Sea-ice-related halogen enrichment at Law Dome, coastal East Antarctica

Paul Vallelonga1, Niccolo Maffezzoli1, Andrew D. Moy2,3, Mark A. J. Curran2,3, Tessa R. Vance3, Ross Edwards4, Gwyn Hughes4, Emily Barker4, Gunnar Spreen5, Alfonso Saiz-Lopez6, J. Pablo Corella6, Carlos A. Cuevas6, and Andrea Spolaor7,8 Paul Vallelonga et al.
  • 1Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, Copenhagen Ø 2100, Denmark
  • 2Australian Antarctic Division, Channel Highway, Kingston, TAS 7050, Australia
  • 3Antarctic Climate and Ecosystem Cooperative Research Centre, University of Tasmania, Private Bag 80, Hobart, TAS 7001, Australia
  • 4Physics and Astronomy, Curtin University of Technology, Kent St, Bentley, WA 6102, Perth, Australia
  • 5University of Bremen, Institute of Environmental Physics, Otto-Hahn-Allee 1, 28359 Bremen, Germany
  • 6Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain
  • 7Ca'Foscari University of Venice, Department of Environmental Sciences, Informatics and Statistics, Via Torino 155, 30170 Venice Mestre, Italy
  • 8Institute for the Dynamics of Environmental Processes, IDPA-CNR, Via Torino 155, 30170 Venice Mestre, Italy

Abstract. The Law Dome site is ideal for the evaluation of sea ice proxies due to its location near to the Antarctic coast, regular and high accumulation throughout the year, an absence of surface melting or remobilization, and minimal multiyear sea ice. We present records of bromine and iodine concentrations and their enrichment beyond seawater compositions and compare these to satellite observations of first-year sea ice area in the 90–130° E sector of the Wilkes coast. Our findings support the results of previous studies of sea ice variability from Law Dome, indicating that Wilkes coast sea ice area is currently at its lowest level since the start of the 20th century. From the Law Dome DSS1213 firn core, 26 years of monthly deposition data indicate that the period of peak bromine enrichment is during austral spring–summer, from November to February. Results from a traverse along the lee (western) side of Law Dome show low levels of sodium and bromine deposition, with the greatest fluxes in the vicinity of the Law Dome summit. Finally, multidecadal variability in iodine enrichment appears well correlated to bromine enrichment, suggesting a common source of variability that may be related to the Interdecadal Pacific Oscillation (IPO).

Short summary
We present a study of bromine, iodine and sodium in an ice core from Law Dome, in coastal East Antarctica. We find that bromine and iodine variability at Law Dome is correlated to changes in the area of sea ice along the Law Dome coast as observed by satellite since the early 1970s. These findings are in agreement with a previous study based on MSA and confirm a long-term trend of sea ice decrease for this sector of Antarctica over the 20th century.