Text and photos: Henry Patton
Our final 24 hours of this research expedition will shift focus from hydrocarbon-based aspects to a more glaciological perspective. This also means a transit to a new area, to the nearby glacial trough of Sentralbankrenna, which around 15,000 years ago hosted one of the last major outlet glaciers of the retreating Barents Sea ice sheet. As the Earth thawed at the end of the last ice age, rising air and ocean temperatures triggered the collapse of the once 3-km thick ice sheet that covered most of the Barents Sea and NW Europe. Sentralbankrenna was one of the last areas to deglaciate due its location in the central Barents Sea, and so the geological information left behind here can tell us much about the processes of why and how such large marine-terminating glaciers can disappear under times of rapid climate change.
I visited this area previously in 2020, where we managed to collect some multibeam echosounder data showing some tantalising snapshots of the glacial deposits and landforms left behind on the sea surface. Our plan is to supplement this data and fill in some of the many gaps still left behind – yet with limited time on our side and Sentralbankrenna being a very large trough some 100 km wide, our decision for where to survey becomes remarkably difficult.
Figure 1: Multibeam echosounder (MBES) data tells us what the seafloor looks like in high resolution. In Sentralbankrenna our swath – our window of the seafloor – is c. 1 km wide. Source: Wikipedia.
After some debate on the best strategy we decide to focus on two areas, one over what appears on low resolution data to be an interesting complex of hummocky topography where a glacier may have once terminated, and the other over what could be a subglacial channel where water may have flowed below the ice sheet. Clues published from elsewhere in this region indicate that abundant meltwater reaching beneath the glacial ice was a key characteristic of these systems as they collapsed.
Figure 2: Where to survey? Relatively low-resolution imagery of the seafloor (IBCAO) provides tantalising clues of the glacial deposits present. This area in the southern part of the trough is c. 120 km wide, giving a clue as to the scale of the glacial ice that used to exist here.
Then, disaster strikes! With data streaming in, the captain suddenly informs us he needs to stop the ship immediately – there’s some trouble with the engine. The ship’s engineers soon report back that they need to replace a part and change some 4,000 litres of oil. It won’t be a quick job but it seems at least we won’t be stranded in the middle of the ocean for long. After some hours the engine restarts and with some relief we can resume sailing, with our bearing now firmly fixed on a return back to Tromsø.
Although the data collection was abruptly cut short, what we found showed some very interesting information, and as usual its interpretation raises even more questions on what happened here thousands of years ago. This certainly won’t be our last visit here.
Figure 3: Sailing back to Tromsø with a fixed engine. The colour of the sea is remarkably turquoise, an indication of the abundant phytoplankton blooming in the area.