title: Canadian Arctic sea ice reconstructed from bromine in the Greenland NEEM ice core.
abstract: Reconstructing the past variability of Arctic sea ice provides an essential context for recent multi-year sea ice decline, although few quantitative reconstructions cover the Holocene period prior to the earliest historical records 1,200 years ago. Photochemical recycling of bromine is observed over first-year, or seasonal, sea ice in so-called "bromine explosions" and we employ a 1-D chemistry transport model to quantify processes of bromine enrichment over first-year sea ice and depositional transport over multi-year sea ice and land ice. We report bromine enrichment in the Northwest Greenland Eemian NEEM ice core since the end of the Eemian interglacial 120,000 years ago, finding the maximum extension of first-year sea ice occurred approximately 9,000 years ago during the Holocene climate optimum, when Greenland temperatures were 2 to 3 °C above present values. First-year sea ice extent was lowest during the glacial stadials suggesting complete coverage of the Arctic Ocean by multi-year sea ice. These findings demonstrate a clear relationship between temperature and first-year sea ice extent in the Arctic and suggest multi-year sea ice will continue to decline as polar amplification drives Arctic temperatures beyond the 2 °C global average warming target of the recent COP21 Paris climate agreement.
authors.affiliation: Ca'Foscari University of Venice, Department of Environmental Science, Informatics and Statistics, Via Torino 155, 30172 Mestre, Venice, Italy.|Institute for the Dynamics of Environmental Processes, IDPA-CNR, Via Torino 155, 30172 Mestre, Venice, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Spolaor
authors.affiliation: Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, Copenhagen Ø 2100 Denmark.
authors.forename: Paul
authors.initials: P
authors.lastname: Vallelonga
authors.affiliation: Institute for the Dynamics of Environmental Processes, IDPA-CNR, Via Torino 155, 30172 Mestre, Venice, Italy.
authors.forename: Clara
authors.initials: C
authors.lastname: Turetta
authors.affiliation: Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, Copenhagen Ø 2100 Denmark.
authors.forename: Niccolò
authors.initials: N
authors.lastname: Maffezzoli
authors.affiliation: Institute for the Dynamics of Environmental Processes, IDPA-CNR, Via Torino 155, 30172 Mestre, Venice, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Cozzi
authors.affiliation: Institute for the Dynamics of Environmental Processes, IDPA-CNR, Via Torino 155, 30172 Mestre, Venice, Italy.
authors.forename: Jacopo
authors.initials: J
authors.lastname: Gabrieli
authors.affiliation: Ca'Foscari University of Venice, Department of Environmental Science, Informatics and Statistics, Via Torino 155, 30172 Mestre, Venice, Italy.|Institute for the Dynamics of Environmental Processes, IDPA-CNR, Via Torino 155, 30172 Mestre, Venice, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Barbante
authors.affiliation: National Institute of Polar Research, 10-3 Midori-cho, Tachikawa Tokyo, 190-8518, Japan.
authors.forename: Kumiko
authors.initials: K
authors.lastname: Goto-Azuma
authors.affiliation: Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Saiz-Lopez
authors.affiliation: Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Cuevas
authors.affiliation: Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, Copenhagen Ø 2100 Denmark.
authors.forename: Dorthe
authors.initials: D
authors.lastname: Dahl-Jensen