Temporal Variability of Dissolved Aluminum in the Northern Gulf of Alaska

Dissolved aluminum is a tracer of continental input to the surface ocean, and in the Northern Gulf of Alaska (NGA) highly elevated aluminum concentrations have been reported along coastal freshwater plumes in late summer that result from high glacial and riverine input. These values present a contrast to dissolved Al concentrations of the offshore NGA, which may on the order of 1 nM or less and are some of the lowest values found in the world ocean. Tracing the spatial and seasonal variability of freshwater input to the Gulf of Alaska and its influence over the shelf ecosystem will help advance current hypotheses being tested in the newly established NGA Long Term Ecological Research (LTER) Site. Here we present dissolved Al distributions obtained seasonally (spring, summer and fall) during 2018 NGA LTER cruises and a summer 2019 Copper River Plume study. Samples were analyzed via inductively coupled plasma mass spectrometry and range over 4 orders of magnitude from subnanomolar values offshore up to values >100 nM further inshore. Results are discussed in terms of seasonal and interannual variation, highlighting the role of coastal circulation in trapping the freshwater input of dissolved Al and other trace elements along the shelf.