Discovery of a Major Medieval Glacier Lake in Svalbard

Map of Svalbard with the location of the ancient lake marked at Braganzavågen, a bay in the van Mijenfjorden fjord on the island of Spitsbergen. (Source: National Geospatial-Intelligence Agency/Google Earth).

Up in the Norwegian archipelago of Svalbard, ice and glaciers cover around 60 percent of the area and have long defined its geographical formation and ecological integrity. One major glacial process that has transformed the Svalbard landscape is glacier surging, a short-lived event of extremely rapid glacier buildup ranging from a few months to a couple of years. Recently, a team of scientists led by Astrid Lyså published a study in Boreas presenting the story of a dramatic glacier surge during the 14th century that dammed off a stream and created a temporary lake in inner van Mijenfjorden at Braganzavågen. The authors report, at its fullest size, the short-lived lake was the largest of any known lake in the entire archipelago for the last 10,000 years at an estimated 77 square kilometers.

In Svalbard, “the glaciers are shaping the landscape on all scales, from eroding the large fjords to small scratches and striations on bedrock surfaces,” says Eiliv Larsen of the Geological Survey of Norway, one of the scientists involved in the study. However, according to the study, it is uncommon for glacier surging to result in lake damming and difficult for scientists to detect them. “The recognition of short-lived lake events is challenging in general, and even more so when a lake became dammed as a result of a surging glacier,” states the study.

One of the important components of analyzing surge-type phenomenon included sedimentary rock formations found at the bottom of the ancient lake. But knowledge of the existence of short-lived lakes from the sedimentary record is “difficult to establish due to the relatively poor preservation potential of shorelines, spillways and thin coverings of lacustrine sediments that constitute evidence of their presence,” adds Fiona Tweed, a professor of geography at the Staffordshire University in the United Kingdom, who spoke to GlacierHub about the findings. “These traces are unlikely to survive in environments where subaerial processes are highly active on glacier retreat.”

Mouth of a glacier at Svalbard (Source: GRID Arendal/Flickr).

Thus, the study required the cooperation of various types of historical, geomorphological, as well as geological information to figure out the life of this particular lake. In addition to the sedimentary records, geomorphological mapping through the analysis of paleo-shoreline remnants helped scientists understand the extent of the lake and its evolution and decay. Sediment core analyses elaborated on the mapping by detecting environmental changes on the fjord from a bay, which became a freshwater lake when cut off by the surging glacier, and its return to a tidal flat of the fjord. Witold Szczuciński, another scientist involved in the study from the Adam Mickiewicz University in Poznań, Poland, explained how geochronology was the key in bringing all the data together as well as a good understanding of the system, including the interactions and limitations of each component.

“Compiling geological data is very often like a puzzle, and the challenge is to fit the pieces together,” Larsen told GlacierHub. “This research was definitely of that sort, and it is a process that starts in the field, making observations and collecting samples and data, going via analyses and many trials and discussions before a final result.”

For many scholars in the field, the compilation of information is what made this study so remarkable. “For me, the significance of this work lies in the holistic, multidisciplinary approach that has been used to decode the landform and sedimentary evidence,” Tweed said.

In addition to the cause of its unusual formation, another phenomenal component of the lake was how quickly it formed. Perhaps the most impressive finding was how short-lived the lake was, possibly just one season, and the enormous size of the end moraine system deposited during the surge. “This is really footprints of very active and strong forces at play,” Larsen said.

Wesley Farnsworth, a Ph.D. candidate at the University Center in Svalbard and the Arctic University of Norway, Tromsø, told GlacierHub that this was not the first study from Svalbard to focus on a paleo-ice-dammed lake. There are numerous such events, deposits, and histories that remain undocumented and unstudied in the region. “I find it particularly intriguing that relatively short-lived events can have such an extended impact on the landscape,” he said. “Glaciers and ice caps can be valuable indicators for past climate, making them key archives for extending our understanding of temperature and precipitation beyond the instrumental record.” For example, studying past changes in high latitude glaciers allows a better understanding of the role of the Arctic in the global climate system and aids scientists in more effectively predicting antecedent climate scenarios.

Although most glaciers across the world are retreating, many of Svalbard’s glaciers demonstrate surge patterns similar to the one that led to the lake formation 700 years ago. The study notes both scientific and practical reasons for deepening our understanding of these phenomena, in particular, the fact that damming and draining of these lakes can pose hazards to humans and infrastructure. Szczuciński told GlacierHub that various estimates state 13 to over 90 percent of Svalbard’s glaciers are surge-type and undergo the cyclical rapid advances followed by longer periods of retreat.

Given how fast and extensive this ancient lake formed in the 14th century due to a surging glacier, studies on past glacial activities are quintessential to understanding glacier surge events and how they could impact society in the face of a changing climate.