The Arctic Ocean is a key area of global climate change and has been undergoing drastic changes in the recent decade. As a moderator between the atmosphere and the ocean in the polar regions, sea ice is one of the most important components of the global climate system. But the Arctic sea ice cover is diminishing rapidly, and because the climate system is so complex, we cannot easily figure out why that is and what it means. To make matters worse, obtaining in-situ observations in a remote and extreme environment such as the central Arctic Ocean is a great challenge for man and machine. But without comprehensive and year-round measurements, the climate processes that lead to the drastic changes will remain elusive.
This situation has changed with the advance of new technologies in recent years. Autonomous and robotic instrumentation for example can be used to fill these knowledge gaps.
Robotic underwater technologies have evolved significantly in recent years, enabling the comprehensive study of upper ice-covered ocean processes using remotely operated underwater vehicles (ROVs) for the first time. A ROV is controlled through a several hundred meter long cable and can dive beneath the sea ice to observe processes which are crucial for the fluxes of energy, momentum and matter across the atmosphere-ice-ocean boundary. They can for example be used to study the transmission of solar energy through the ice and snow layers, which cause a warming of the upper ocean and melting of the ice itself. Light is also a key factor for in and under-ice primary production, supplying the ice-associated food chain, and causing carbon export to deeper water layers and the sea floor.
During the Arctic Ocean 2018 expedition, we used a new ROV system with a diverse scientific sensor payload to record the spatial variability of key parameters close to the ice-ocean interface, and record their temporal evolution during the transition from a pond-covered sea ice regime in summer to a snow-covered white desert in autumn (also referred to as “freeze-up”). Our observations revealed that, although the light intensity decreased significantly as more snow accumulated on the sea ice, the ice-associated algae attached to the ice underside were still thriving, a quite unexpected and puzzling finding.
The observations obtained during this expedition are a critical piece to painting a more comprehensive picture of the changes happening in the Arctic, ultimately improving our understanding of climate change.
Alfred Wegener Institute