Splitting Icebergs: How sediment affects iceberg melt

Sediment-laden icebergs are a primary mechanism involved in the long-distance transport of terrestrial sediment in the marine environment. Indeed, there is evidence icebergs transported sediment >2000km across the North Atlantic during the last glaciation. In addition, iceberg 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 constrained. Here we present the first laboratory investigation into the impacts of sediment on the melt rate of icebergs. By moving freezer-made icebergs through a tank filled with sea water we tested how different sediment diameters and distributions affect iceberg melt rates. We identify a new iceberg deterioration mechanism in which the presence of sediment within an iceberg causes it to break into multiple pieces, increasing the overall melt rate. A strong dependence between the diameter of sediment particles and melt rate of iceberg is also identified. Using these findings, a predictive model capable of determining when an iceberg will break into multiple pieces was developed, allowing for better parameterization of icebergs and increased accuracy of climate models.