Carbon and nutrients in rivers of the North Slope Amy Townsend-Small and James McClelland The University of Texas at Austin

The Arctic is the most river-influenced ocean Science Dec Importance of Arctic Rivers

The Carbon Cycle and Global Warming

The Arctic and Climate Change Arctic ecosystems are expected to be disproportionately affected by global warming. Photo by Breton Frazer

How the Arctic controls global climate As the Arctic Ocean gets fresher and warmer, North Atlantic Deep Water formation will slow or stop

Importance of rivers for ocean chemistry Terrestrial nutrients introduced to the Arctic Ocean during the spring thaw are responsible for incredible amounts of productivity offshore.

Human Impacts on Rivers Many rivers of the world suffer from an excessive input of anthropogenic nutrients. North Slope rivers are some of the cleanest rivers in North America. –Studies of these ecosystems before major human and climate impacts is important to evaluate future changes.

Mississippi River Delta, Lousiana, USA

Rivers and global carbon cycling Particulate organic carbon introduced to the ocean via rivers is often buried in sediments, removing it temporarily from the global C cycle. NASA Earth Observatory Yangtze River Delta, China

Driving Question How do changes in river discharge affect delivery of organic matter and nutrients to the Arctic Ocean? Photo by Breton Frazer

Approach Measure concentrations and composition of nutrients and dissolved and particulate organic matter in rivers throughout the hydrograph. These measurements will be combined with discharge and climate data to model future changes in C, N, and P delivery to the Arctic Ocean. Photo by Breton Frazer

Study Area

Upper Kuparuk Sagavanirktok River Kuparuk River Colville River Toolik Field Station

Inorganic nitrogen in rivers NH 4 + (  M)

Dissolved phosphate in rivers PO 4 3- (  M) NH 4 + peak

Total suspended solids TSS (mg/L)

Alkalinity in rivers

What happens during break-up? Ammonium and phosphate are high –Source: Runoff Nitrate is expected to be lower at higher discharge Alkalinity is diluted during the spring melt TSS is exponentially higher during the breakup. Sediments are mobilized during fast water movement. Photo by Breton Frazer

Differences between rivers The Kuparuk River is not influenced by glaciers –TSS and alkalinity are lower The Colville is the largest river, and it flows all year under the ice. –Explains higher nutrient concentrations? Constituent concentrations are higher at the Kuparuk mouth than at the headwaters Photo by Breton Frazer

Organic matter dynamics How much organic matter mineralization happens in transit to the ocean? –REU project: Lability of DOC –Stable isotopic composition of C fractions POC, DOC, and CO 2 These measurements will help us determine how much terrestrial OC makes it to the ocean

Thanks! National Science Foundation The University of Texas Marine Science Institute Co-PIs: Bruce Peterson, Max Holmes, and Marc Steiglitz Breton Frazer Jorge Noguera, Adrian Green, and Christie Haupert