Melting ice, habitat change and nutrient flux: Hydrological, biogeochemical and biological linkages between the Copper River and coastal Gulf of Alaska

OBJECTIVES:

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. It will examine present-day relationships between landscape, nutrient supply, and ecosystem productivity. The Copper River and northern GoA supports several commercial fisheries; however, the ecosystem has been little studied. This project will fill several data gaps, will increase our understanding of how this complex system is driven by climate change, and will improve our ability to manage resources
important for local economies.

In the Copper River Basin, we will conduct CO2 exchange measurements in 5 landscapes that represent the major ecosystem types following deglaciation, and we will quantify 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 will be complemented by stream water sampling from the 5 vegetation types, 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 will focus 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 will 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 will be able to begin to describe how this productive ecosystem will be affected by different patterns of climate change. Beyond the plume, we will investigate the role of aerosol iron transport from the Copper River watershed to the GoA.

Many of the data requirements of this project will be fulfilled with NASA data and imagery products, including land and ice cover, sediment loading, dust and aerosol transport, and the timing and extent of physical oceanographic features and marine productivity. Several of the data products include time series that will be used retrospectively to examine how recent climate shifts have impacted the ecoregion. The team is interdisciplinary, including geographers, geochemists, biologists and oceanographers.