A New Deterioration Mechanism for Icebergs

Icebergs are a primary mechanism for the long-distance transport of terrestrial sediment in the marine environment. During the last ice age, icebergs transported sediment more than 2000 km across the North Atlantic. In addition, sediment plays a key role in marine nutrient fertilization, phytoplankton growth, and CO2 drawdown. However, the effect sediment has on the deterioration of icebergs, as well as rates of sediment loss to the marine environment, are poorly understood. Here we present a completely new mechanism for iceberg deterioration which has previously gone undiscovered. We conducted the first laboratory investigation into the effects of sediment on iceberg deterioration and found that it increases the melt rate in three ways. First, as expected, there is less ice to melt. Second, a sediment plume may form which enhances the heat flux towards the ice. Third, sediment layers induce an iceberg to break into multiple pieces, dramatically increasing the overall rate of ice melt. The latter mechanism has never been reported previously. Our results provide a parametrization that includes the effects of sediment on iceberg deterioration. Our findings have significant implications for more accurately modeling iceberg break-up and for the potential of icebergs melt water to trigger abrupt climate change.