Although gap layers in Antarctic sea ice had already been observed and recognized as a growth habitat for algae and a refuge for larger organisms (as well as a source of food), this is the first time that the way the layers form has been quantified. "How they contributed to sea ice melting and the contribution of this melt to the freshwater flux into the ocean had not previously been reported," explained Ackley.
The team, which includes scientists from the Southwest Research Institute in San Antonio, Texas, and the Desert Research Institute in Reno, Nevada, devised a heat transfer mechanism for how the gap layers form. "This mechanism is a common result of ice cover seasonal warming, " Ackley told environmentalresearchweb. "It also suggests that the layers will be widespread in the Antarctic summer sea, as well as being a usual habitat for the organisms found there."
Ackley added: "The model should now be included in sea ice models – something that would allow researchers to predict how the Antarctic habitat might evolve as the climate warms."
Summer sea ice is an important habitat for polar marine life, such as algae, krill, seals and penguins. As the climate warms, however, there are concerns that reduced sea ice might seriously affect such Antarctic ecosystems.
Gap layers are partially melted honeycomb-like ice matrices filled with seawater that form in sea ice below a surface layer of snow and ice. They are dark in colour because they contain many algae and microbes. The researchers analysed the reversal in near-surface temperature gradients in the sea ice and the thermal conductivity of upper ice columns, and calculated that the gap layer forms at a rate of up to 0.75 cm per day.
The work was published in Geophysical Research Letters.