The coastal Gulf of Alaska (GoA) region is experiencing accelerating climate change as manifested by rapid recession of glaciers; climate models predict up to a 40% increase in river runoff from Alaska rivers by 2050. Over coming decades an increase in glacier-dominated river discharge is likely, followed by decreases as glaciers recede. Changes in freshwater discharge are likely to alter the flux of particulate micronutrient iron from glacier dominated rivers to the ocean, as well as nitrate fluxes to surface water from estuarine upwelling, with cascading effects throughout the ecosystem. The freshwater supply of dissolved organic nitrogen (DON) and
nitrate may also increase over time due to colonization of deglaciated watersheds by nitrogen-fixing plants. The objective of this project is to evaluate the physical changes currently occurring in watersheds of the Copper River region attributable to melting ice and climate change, and examine their impact on the Copper River plume extending into the GoA/
In the Copper River Basin, we are conducting CO2 exchange measurements in landscapes that represent the major ecosystem types following deglaciation, and we are quantifying their associated vegetation indices, allowing for scaling and forecasting as further landscapes become ice free and these systems transition into new habitats as warming continues. Estimates of CO2 exchanges are complemented by stream water sampling, allowing for quantification of C and N inputs into the aquatic system as ecosystems become ice free and they transition from one type to another during ecological succession. In the Copper River plume, work is focussing on oceanographic surveys to be carried out in a series of short cruises extending out from the Copper River mouth beyond the shelf break, used to ground-truth satellite observations that provide more complete spatial and temporal coverage. By conducting sampling events over intra- and interannual intervals under conditions of very different glacial meltwater inputs to the coast, we are beginning to describe how this productive ecosystem will be affected by different patterns of climate change. Beyond the plume, we are also investigating the role of aerosol iron transport from the Copper River watershed to the GoA, by tracking dust transport events with satellite observations and modeling, and sampling aerosols with a particle collector deployed on Middleton Island.
