ABSTRACT:

Sea ice is an active component of the Earth’s climate system, interacting with both the atmosphere and the ocean. However, a thorough understanding of its annual impact on exchanges of gases, with potential feedback on the climate, is still missing. Arctic sea ice is commonly covered by melt ponds during late spring and summer, with strong effects for sea ice physical and optical properties. Yet, little is known on how melt pond formation affects sea ice gas dynamics, with consequences for gas exchanges between sea ice and the atmosphere. Here we show how melt pond formation and meltwater percolation through the ice affect sea ice physical properties and sea ice gas composition with impacts on sea ice CO2 exchange with the atmosphere.
Sea ice gas composition was mainly controlled by physical processes, with most of the gas being initially in the gaseous form in the upper ice layer. As sea ice warmed up, the upper ice gas concentration decreased, suggesting a release of gas bubbles to the atmosphere. However, as melt ponds formed, the ice surface became strongly depleted in gases. Due to the melt ponds development, meltwater percolated through the ice thickness resulting in the formation of an underwater ice layer also depleted in gases. Sea ice, including brine, slush, and melt ponds, was undersaturated in CO2 compared to the atmosphere, supporting an uptake up to –4.26 mmol m–2 d–1 of atmospheric CO2. However, this uptake weakened in the strongly altered remaining ice surface (the 'white ice') with atmospheric uptakes averaging –0.04 mmol m–2 d–1 as melt ponds formation progressed.

ABSTRACT:

Landfast sea ice biogeochemical properties and in the Bothnian Bay (Northern Baltic Sea) and concentrations of greenhouse gases, including carbon dioxide ( (CO2, ), methane (CH4, ) and nitrous oxide (and N2O) in both sea ice and water column.
Data from Geilfus et al (2021) submitted to Elementa: journal of the anthropocene, Potential role of the landfast sea ice in the Bothnian Bay (Baltic sea Sea) ice:as a temporary storage compartment for greenhouse gases.

ABSTRACT:

Here we report how inputs of meteoric water affect the physical and biogeochemical properties of both the water column and sea ice cover on the Wandel Sea shelf, northeastern Greenland, during spring 2015. Depleted 18O observed in the water column, with surface water as low as –16.3 ‰, suggest a strong input of meteoric water (i.e., water derived from precipitation). Depleted 18O observed within sea ice (from –21.5 to –8.0 ‰) reflect its formation from already depleted surface water. In addition, the thick snow cover present during the survey promotes the formation of snow ice as well as insulates the ice cover. Within sea ice, the relatively warm temperature and low salinity impeded impedes ikaite formation. However, measurements of total dissolved inorganic carbon and total alkalinity indicate the dissolution of calcium carbonate as the main process affecting the carbonate system in both sea ice and the water column. Therefore, we propose that carbonate minerals, released along with glacial drainage, dissolve in both sea ice and the water column, affecting the carbonate system. This suggests that increasing inputs of glacial meltwater may compensate for the lack of ikaite precipitation within sea ice by increasing glacier-derived carbonate minerals to the ocean and incorporation within the ice structure. If widespread in glacial-fed waters, bedrock carbonate minerals could increase CO2 sequestration in glacial catchments despite the weakening of the sea ice carbon pump.