Research overview

Since 1979, the Arctic has warmed nearly four times faster than the global mean [1]. Recent mass loss from Arctic glaciers has contributed to sea level rise at a comparable rate to the vast Greenland Ice Sheet [2]. The loss of glaciers is also expected to have numerous local impacts on hydrological, ecological, and human systems. Despite these global and local scale consequences, large uncertainties remain in projections of glacier loss this century. My research program draws on tools from paleolimnology, glacial geomorphology, climate and glacier modeling, and remote sensing and spatial analysis to investigate past (Holocene and historical), contemporary and future (twenty-first century) climate and cryosphere change across the circumpolar North.

Recent and ongoing research themes

Holocene climate and glacier reconstruction

My recent work has largely focused on analysis of physical and geochemical properties of glacial lake sediment to infer changes in glacier size over the Holocene in understudied regions of Greenland. In general, a dominant input of inorganic, fine–grained (silty–clays), blue–gray sediment is indicative of the presence of a glacier or ice cap in the catchment, whereas sediment that is brown in color and higher in organic material (i.e., gyttja) is associated with no glacier or ice cap (or an insignificant activity) in the catchment. I use these sedimentary indicators alongside a glacier mass–balance parameter, the equilibrium–line altitude (ELA), as well as geomorphic evidence of past glacier extent—e.g., the positions of moraines and trimlines, to model past glacier surfaces and develop quantitative reconstructions of past climate from lake records.

Historical glacier change

Owing to their remote and logistically challenging setting, direct field measurements on glaciers in Greenland are very rare, and long–term (multi–decadal) field–based mass–balance observations only exist for one glacier beginning from the mid–1990s (i.e., Mittivakkat Glacier in southeast Greenland). Rather, most studies on Greenland’s glaciers have relied on satellite imagery and other space–based observations to estimate glacier area, volume, or length change. Although these types of studies have greatly improved our knowledge of very recent glacier change in Greenland, they are inherently restricted to the satellite era, which began in the late 1970s. This limitation hinders our longer–term understanding of glacier sensitivity to climate perturbations, with implications for prediction of their response to sustained warming as anticipated for the future. I combine historical observations (air photos) with modern satellite imagery to extend the limited time frame of observational records of glacier change from understudied regions in Greenland.

Assessing glacier lifespans

While global–scale studies address total glacier and ice cap mass loss and their contribution to rising sea–level by the end of the century, in general they do not focus on sub–regional trends in ice loss over time, nor do they predict when individual glaciers and ice caps will melt away. In my NOAA Climate & Global Change (C&GC) postdoctoral fellowship, I am working to develop the first Arctic–wide prediction of glacier and ice cap lifespans, providing a regionally differentiated picture of past and future change. Specifically, I am workinig to model when individual glaciers and ice caps ELAs crossed, and will cross, critical topographic thresholds (which equate to glacier birth and death) between 7 ka and 2100 CE. This work will thereby estimate how long individual glaciers have existed on the landscape and will forecast the timing of the demise of the Arctic’s 50,000+ glaciers and ice caps, while identifying which are most at risk of melting away first under different future warming scenarios.

Cirumpolar data synthesis

To date, there are relatively few continuous records of glacier and ice cap variations inferred from glacial lake sediments over the Holocene across the Arctic—a vast area, which hosts a wide range of modern climates. I have recently compiled all available lacustrine glacier and ice cap records (n = 66) from seven Arctic regions. The work summarizes evidence for when glaciers were smaller than today or absent altogether, indicating warmer than present summers, and evidence for when glaciers regrew in lake catchments, indicating summer cooling. Most importantly, the synthesis strongly reinforces that relatively modest summer warming (compared with projections of larger future climate change) drove major environmental changes across the Arctic including the widespread loss of glaciers and ice caps.




References:

  1. Rantanen, Mika, et al. "The Arctic has warmed nearly four times faster than the globe since 1979." Communications Earth & Environment 3.1 (2022): 1-10.

  2. Meredith, M., et al. "Polar Regions. Chapter 3, IPCC Special Report on the Ocean and Cryosphere in a Changing Climate." (2019).