The two APRI members Jakob Abermann (Graz University) and Rainer Prinz (Innsbruck University) visited the vertical ice cliffs of Northwest Greenland in 2017 and observed changes in ablation since the 1950's.
The impressive near-vertical ice cliff is part of a land-terminating glacier of the Nunatarssuaq ice cap. The area where the almost 30 m tall ice cliff is situated has been named the Red Rock Ice Cliff due to its visible red color. The focus was on the glacier changes which they could compare with archival data from the 1950s and 1960s, in order to derive subtle changes, too small to be detected with satellite observations.
The study area in Northwest Greenland with the Nunatarssuaq Ice Cap and the Greenland Ice Sheet (Axford, et al. 2019)
“Detailed maps of the vertical ice margin, observations of its development over a decade and ice temperature measurements combined with ablation stakes are documented in previous publications.”
Satellite map of the study area in Northwest Greenland with the Nunatarssuaq Ice Cap and the Greenland Ice Sheet (Abermann et al. 2020)
Historical data for comparison
The survey around the Red Rock Ice Cliff started in the mid-1950’s by American scientists related to the military activities in Northwest Greenland around the Thule Air Base. One of their surveying goals was to explore possible access routes to the Greenland ice-sheet. American polar expeditions in Greenland started after the German occupation of Denmark in the early 1940’s. During World War II, the Danish government signed a treaty with the United States authorizing American protection of the Danish colonies, which led to military installations in Greenland. Thule Air Base quickly became a key point in the American nuclear geostrategy due to its location about halfway between Washington and Moscow. Expeditions onto the Greenland ice-sheet were made with the goal to build the top secret Camp Century. The American field expeditions took place between 1955 and 1965 and led to highly detailed geodetic, glaciological, and atmospheric data.
Photographs from the campaigns in 1955 and 2017: (a) Hilty (1956) and from the approximate location in 2017 (b) from Abermann et al. (2020).
Although Red Rock Ice Cliff has been sporadically visited since then, the APRI scientists saw it as a good opportunity to combine six decades of scattered documented data to better understand the climate drivers of the recent widespread thinning of the Greenland ice margin. The locations captured on the old photos from the 1950’s expedition could be revisited. Photographs show a major change in the slope and shape of the ice cliff, which has become less inclined and smoother due to ablation.
Ice cliff thickness fluctuations
The authors suggest that the interannual thickness fluctuations are essentially related to changes in summer air temperature and precipitation, when cold and dry periods used to be related to occasions when the ice cliff lost least mass. However, this pattern is broken in very recent years. Despite the increased precipitation in the region since the beginning of the records, higher air temperatures accelerate enhanced melt, consequently leading to the thinning of the ice cliff. In addition, the mass of excessive precipitation may also impact the recent geometry changes. Other factors, such as long-term warming, increasing rainfall over the Red Rock region or changes in the glacier’s thermal regime can be relevant too. This implies that the data collected during the 2017 expedition are yet insufficient to fully understand the complex drivers for the subtle changes observed. Yet, their existing findings serve as a motivation for future campaigns.
Further photographs from the campaigns in the 1950s and 1960s: (c, e) Hilty (1956); (g) Fristrup (1963) and from the approximate locations in 2017 (d, f, h) from Abermann et al. (2020).
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