Marine Aerosol Records of Arctic Sea‐Ice and Polynya Variability From New Ellesmere and Devon Island Firn Cores, Nunavut, Canada.

Sea ice plays a critical role in the Earth's climate system, including influencing ocean heat uptake, reflecting solar radiation, and contributing to dense water formation. Instrumental records of polar sea ice extent are only available since 1979, however. The short length of such records also limits our knowledge of polynya variability, which can reflect large‐scale atmospheric and climate changes. Ice core proxy records can extend these observations, but require further development and regional validation. We compare chloride and methanesulfonic acid concentrations from two new firn cores from the Canadian Arctic with satellite‐derived observations of regional sea‐ice concentration and polynya variability from 2002 to 2014. The sub‐annual resolution of these cores allows for detailed investigation of how regional sea‐ice concentration is recorded in the ice at Prince of Wales Icefield (POW), Ellesmere Island and Devon Ice Cap (DIC), Devon Island, Nunavut. Over the period 2002–2014 we find that the primary sources of marine aerosols to POW are polynyas within Arctic Canada and the Canada basin of the Arctic Ocean, whereas the primary sources of marine aerosols to DIC are a broader region of the Queen Elizabeth Islands, Baffin Bay, and the Arctic Ocean. Marine aerosol sources to the two core sites are distinct, reflecting different moisture source regions and, likely, differing transport pathways. Air mass back trajectory results support the satellite‐derived results. Glaciochemical records from this dynamic, warming region may provide a proxy for reconstructing North Water polynya and other regional polynya and shore‐lead variability prior to the satellite era. Plain Language Summary: Sea ice plays a critical role in the Earth's climate system, yet instrumental records of polar sea ice extent are only available since 1979. The chemistry of ice cores can extend these observations farther back in time, but need to be validated over the satellite era first. In this study, we compare marine aerosol records from two new cores from the Canadian high Arctic with satellite‐derived observations of regional sea‐ice concentration from 2002 to 2014. Ice cores from this vital region are sparse, and recent surface warming across the Queen Elizabeth Islands heightens the urgency to develop histories of regional sea‐ice and environmental variability. We find that ice core records from this dynamic and warming region may provide a proxy for reconstructing sea‐ice variability prior to the satellite era in certain key regions of the Canadian Arctic Archipelago. Key Points: Marine aerosols to Prince of Wales, 2002–2014, are derived from Canadian Arctic polynyas and the Canada basin of the Arctic OceanMarine aerosols to Devon Ice Cap are derived from broader regions of the Queen Elizabeth Islands, Baffin Bay, and the Arctic OceanMarine aerosol sources to the two core sites are largely distinct, reflecting different moisture source regions and transport pathways [ABSTRACT FROM AUTHOR]