The impact of sea ice diSappearance on highEr North aTlantic clImate and atmospheric bromiNe and mErcury cycLes

The Higher North Atlantic (HNA), Svalbard and Greenland east coastal regions are experiencing rapid climate change with sustained temperature increases and loss of sea ice. This disappearance of old sea ice is cited as one of the causes of the recent exceptional warming of the Arctic, together with increasing inflow into the Fram Strait of the Atlantic meridional overturning circulation (AMOC). However sea ice not only has a role to play in the energy budget and Arctic amplification of global warming, but it also strongly impacts atmospheric chemical processes in the Arctic. Sea ice is involved in the oxidative capacity of the Arctic atmosphere, injecting in spring enormous amounts of Br radicals. Reactive atmospheric bromine in the Arctic is mainly emitted from first-year sea ice (FYSE) through a series of catalytic reactions called the bromine explosion, which can inject an enormous amount of Bromine radicals into the atmosphere. The massive bromine injection into the Arctic atmosphere was firstly discover in 1987 and this process was intensively studied due to its tropospheric ozone destroying capability, causing so-called ozone depletion events (ODE) and its role in mercury depositional processes through atmospheric mercury depletion events (AMDE).
In the Artic region there is a direct link between sea ice, bromine and mercury and SENTINEL aims to study the effect of the recent sea ice loss on these Arctic chemical processes and not only for its role in the heat transfer. The novelty of the project will go beyond the state of the art for sea ice measurements, by evaluating if sea ice promotes feedback mechanisms able to modify the bromine, mercury and ozone cycles in the Arctic. SENTINEL will consider the role of Br on the atmospheric oxidative capacity, it will improve our understanding of the processes that control the Br atmospheric cycle as well biogeochemical cycles that depend on the bromine atmospheric cycle, such as ozone and mercury. SETINEL will reach its goal by exploit the results that will be obtained from the analysis of two ice cores, one from Greenland and one from Svalbard, able to record the atmospheric condition for the two specific region. Unifying different disciplines in a single project, SENTINEL will evaluate previously unstudied feedback mechanisms of extreme relevance for Arctic amplification and local communities.

The two main objectives of SENTINEL are to evaluate the impact of the sea ice retreat on i) regional climate and the water vapor cycle and on ii) the biogeochemical cycle of bromine and consequently on those of mercury and ozone. The project will be based on two ice core records from Svalbard (Holthedalfonna ice field) and Greenland eastern coast (EGRIP) covering the satellite period (1979 to present). The disappearance of sea ice is expected to have had a direct impact on the water vapor cycle in the HNA, impacting the bromine radical cycle in the atmosphere. This project aims to study changes in the water vapor cycles of the Svalbard and East Greenland coasts using water stable isotope measurements from two ice core records. In parallel, SENTINEL will evaluate the effect of sea ice disappearance on the Arctic bromine atmospheric cycle and on the chain reaction of processes that lead to mercury deposition through Atmospheric mercury depletion events (AMDE) and ozone destruction (Ozone depletion Events). SENTINEL will focus on the effects of this unique abrupt sea ice retreat from the HNA and its possible direct effects on climate and atmospheric chemistry processes, we hope to demonstrate for the first time that sea ice not only has a role to play in the energy budget and Arctic amplification of global warming, but that it also strongly impacts atmospheric chemical processes such as the ozone, bromine and mercury atmospheric cycles.

EGRIP ice core samples measurements complete. A paper is currently under review