Submarine groundwater discharge to the Gulf of Alaska

Monday, April 26, 2021 - 12:20pm
U-Mass Geosciences

Global and near-global estimates of coastal groundwater discharge (CGD) have provided highly variable results that span over an order of magnitude.  Narrowing the scope by focusing on regionally specific processes may provide a more reliable estimate of CGD, as well as more effectively isolate potential CGD hotspots.  This is of particular importance in the Gulf of Alaska (GoA), where complex topography, geology, and climate are coupled with recharge inputs derived from rainfall, snow melt, glacier melt, and glacier volume loss.  Here we estimate CGD to the GoA with a water balance approach that integrates high temporal and spatial resolution recharge inputs over coastal recharge areas.  Surficial geologic maps are incorporated to isolate thick, highly conductive coastal groundwater catchments from catchments composed of bedrock.  We find that CGD contributes a meaningful portion, 2.8%, of the total freshwater flux to the GoA. CGD rates have also been increasing by 0.5% per year over the past 4 decades.  Our findings have broad implications for coastal nutrient and solute fluxes to downstream ecological communities.  Although freshwater discharge to the GOA is well-constrained, the importance of fresh CGD to the GoA has, thus far, been overlooked. 

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