Light absorbing particles (LAP) on glacier surfaces absorb solar energy that is converted to heat that melts or sublimates snow and ice crystals. Increasingly recognized as among the most important LAP, glacier snow and ice algae have been shown to reduce albedo on glaciers in southcentral Alaska, Europe, the Himalaya, and Greenland. Despite their importance, little is known about the ecology of their distribution and abundance, factors that determine where and how many algae exist, and hence the magnitude, extent, and timing of their effects.
We investigated the limiting role of nitrogen and phosphorous in determining snow and glacier ice algae abundance on Eklutna Glacier, an Alaskan glacier with over a decade of continuous glaciological research. We fertilized plots, monitored them with interval photography, and at the season’s end used a very high-resolution satellite image (0.5 m pixel) to calculate an algae abundance index. Results showed a stronger effect on melt for N+P than P alone, and that the 150 m2 area differed significantly from a random sample surrounding the experiment. Moreover, the mean algae abundance index for P-only addition plots did not differ from a random sample surrounding the experiment; however, the mean algae abundance index of N+P addition plots was significantly higher than the mean outside the experimental area. We take this as evidence that Eklutna Glacier’s algae-based ecosystem is N-limited. If other glacial systems are N-limited also, then, given increasing aerosol deposition of N from anthropogenic sources, glacier wastage through algal effects will likely increase over time.
