In September 2017, a large iceberg roughly four times the size of Manhattan calved off of the Pine Island glacier in Antarctica (not to be confused with last July’s massive iceberg that originated from the Larcen C ice shelf further east). While the event itself isn’t that unusual — the Pine Island Glacier accounts for 25 percent of all of Antarctica’s annual ice loss — this iceberg began to break up shortly after separating from its host glacier, instead of doing so after drifting far out into the Southern Ocean, as ‘bergs from Pine Island typically do.
Ordinarily, the bright, white surface of glacial ice found in ice sheets such as the ones that cover Greenland and Antarctica serve to function as reflectors that bounce a certain amount of solar radiation back into space — this effect also helps prevent the ice from being directly warmed too much by the sun. The effect of the ice’s reflectiveness, or albedo, can be compromised by changes in its color, for instance by soot being deposited on the surface from large wildfires ravaging a different part of the globe. The darkening of the ice causes it to absorb more sunlight, and in turn this increases the temperature of the ice, hastening its rate of melt. Now, a new factor has been identified that can darken the albedo of Greenland’s ice: the spread of simple algae.