Wednesday, October 27, 2021

Update on glacier recession


 Oh, how I miss Quelccaya! It has been three years since we've been able to do fieldwork at Quelccaya Ice Cap, a result of removing the AWS and the COVID-19 pandemic. Nonetheless, satellite imagery provides a glimpse at changes continuing at the glacier.

The image pair above illustrates one portion of the ice cap margin as it appeared last week (upper), and just prior to our last visit, in 2018 (lower). The red dots are co-registered to provide a perspective on examples of change over the three years. As in the past, ice recession has not been uniform along the margin. Retreat is especially dramatic at the formerly proglacial lake Morojanicocha. Collaborator Gustavo Valdivia visited this area in September, was able to walk entirely around the lake, remarking that it is "incredible how fast the ice is retreating".

Also note the change in waterlevel at the lake at the top of both images. The obvious drop may reflect seasonal lowering during the June - September dry season, but may also be a response to longer-term hydrological changes associated with ice retreat.

Other environmental changes at Quelccaya are less easy to interpret from imagery at this resolution, such as the magnitude of glacier thinning. Also, changes in the volume
and routing of meltwater runoff from the glacier over time are difficult to assess from imagery, due to the combination of seasonal and diurnal variability, as well as the five-day image acquisition interval.

The landscape around the ice cap supports tremendous biodiversity, due largely to meltwater storage in down-valley lakes and wetlands (bofedales). As the volume of runoff decreases, the many species dependent upon the water are needing to adapt or relocate.

Another change with biotic effects is the glacier-surface morphology, which we have observed over the past two decades. Quelccaya is where breeding by the world's only glacier-nesting bird species has been observed, as described here, here, and here. These Glacier Finch (Idiopsar speculifer, formerly known as White-winged Diuca Finch, Diuca speculifera) will only build nests in crevasses and very steep, fissured margins - both of which tend to disappear as the glacier has thinned and retreated.

We remain optimistic about returning in the next few years to this amazing place, to document and measure changes since our last visit!