In Antarctica, penguin droppings fertilise algae that tint the snow green. This darker snow absorbs more light (up to 40% more solar energy than white snow) and melts faster, a self-sustaining cycle that is worrying researchers on the western Antarctic Peninsula.
How are penguins unwittingly contributing to the melting of the sea ice?
Green snow would thus absorb around 40% more solar energy than clean snow, a gap that, repeated across vast expanses, speeds up the melt.
After their fishing trips, penguins leave droppings rich in phosphate and nutrients on the coastal snow. This guano acts as a natural fertiliser for tiny algae already present in the snow, which then proliferate into dense, verdant blooms.
By fertilising these microalgae, the guano darkens the surface of the snow, which then absorbs more solar energy. The result, in Antarctica, is a local warming loop: the greener the snow becomes, the more heat it captures, and the faster it melts.
Why does greened snow heat up more than white snow?
The algae that colour the snow do more than change its appearance: they alter the way the snow interacts with light. Where clean, white snow reflects most solar radiation, greened patches absorb a far greater share of it.
This phenomenon has a name: the albedo effect, whereby a dark surface absorbs more heat than a light one. According to the study, green snow would thus absorb around 40% more solar energy than clean snow, a gap that, repeated across vast expanses, speeds up the melt.
Can this greening become self-sustaining?
As the algae darken it, the snow absorbs more heat and melts faster. This accelerated melt could in turn favour the spread of those same algae. The cycle would then feed on itself.
Researchers describe this runaway local mechanism as especially pronounced along the coasts of the western Antarctic Peninsula. The phenomenon remains localised, but they believe it now deserves a place in climate projections.
Are researchers already sounding the alarm?
Not yet, and that is the whole nuance of this story. The study, published on 7 October in the Journal of Geophysical Research: Biogeosciences and reported by Ecoticias in an article by François Montcorbier, describes a mechanism that is now well documented, but the researchers themselves are holding back: they are calling for "more field data" before folding it into models of the peninsula's melt. In other words, the evidence exists, but its scale has yet to be measured.
This scientific drip-feed is therefore nothing like a general alarm bell: the phenomenon identified remains localised, and nothing so far suggests it is spreading across the whole continent. Penguins are not being blamed for driving the melt on their own, but their role, until now left out of the calculations, may one day deserve a place in them.
What stands out from this story of penguins and algae is above all how delicate the balances holding the sea ice together really are: an act as trivial as a dropping on the snow can, in a knock-on effect, change how much heat it absorbs. The phenomenon remains confined to the coasts of the western Antarctic Peninsula, and researchers would rather wait for more field data before drawing broader conclusions, even as they judge it already deserves a place in climate projections.
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