Abstract
AbstractIn March and April 2010, we investigated the development of young landfast sea ice in Kongsfjorden, Spitsbergen, Svalbard. We sampled the vertical column, including sea ice, brine, frost flowers and sea water, to determine the CO2 system, nutrients, salinity and bacterial and ice algae production during a 13 day interval of ice growth. Apart from the changes due to salinity and brine rejection, the sea-ice concentrations of total inorganic carbon (CT), total alkalinity (AT), CO2 and carbonate ions (CO32–) in melted ice were influenced by dissolution of calcium carbonate (CaCO3) precipitates (25–55 μmol kg-1) and played the largest role in the changes to the CO2 system. The CT values were also influenced by CO2 gas flux, bacterial carbon production and primary production, which had a small impact on the CT. The only exception was the uppermost ice layer. In the top 0.05 m of the ice, there was a CO2 loss of ∼20 μmol kg-1 melted ice (1 mmol m-2) from the ice to the atmosphere. Frost flowers on newly formed sea ice were important in promoting ice-air CO2 gas flux, causing a CO2 loss to the atmosphere of 140-800 μmol kg--1 d-1 melted frost flowers (7-40 mmol m-2 d–1).
Highlights
Changes in the Arctic Earth System have been reported, and in September 2012 the lowest ice extent on record was observed (Parkinson and Comiso, 2013)
Frost flowers are crystalline structures that form on new sea ice when the air, which is supersaturated with water vapour, condenses at the ice surface
The vertical distribution of salinity in the young-ice cores showed a C-shaped pattern, with higher salinity in the top and bottom ice than in the middle parts, which is typical for first-year ice (e.g. Malmgren, 1927; Thomas and others, 2010), ranging between 14 (22 March) and 10 (31 March) in the top 0.05 m in young ice
Summary
Changes in the Arctic Earth System (e.g. decreased ice extent and thickness) have been reported, and in September 2012 the lowest ice extent on record was observed (Parkinson and Comiso, 2013). Changes in the underlying water will occur during the sea-ice season This is due to the increased CO2 in brine and depletion in AT compared to CT due to CaCO3 precipitation during ice freezing (Rysgaard and others, 2007, 2013; Fransson and others, 2011, 2013) and the excess AT in relation to CT and salinity during ice melt. We present: (1) the evolution of the CO2 system of young sea ice; (2) an estimate of the effect of the biogeochemical processes (e.g. bacterial and primary production and CaCO3 precipitation/dissolution); (3) estimates of CO2 gas fluxes at the ice/air interface; and (4) a discussion of the importance of frost flowers for CO2 transport from the ice to the atmosphere. The radiation measurements of incident PAR showed that 8% remained at a depth of 0.35 m (at midday)
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