Climate Change-Related Hydrologic Variation Affects Dissolved Organic Carbon Export to the Gulf of Maine

Friday, 19 December 2014: 9:40 AM
Thomas Gordon Huntington1, William M Balch2, George Aiken3, Kenna Butler3, Michael Billmire4, Collin S Roesler5, Philip Camill5 and Anna Bourakovsky5, (1)USGS Maine Water Science Center, Augusta, ME, United States, (2)Bigelow Lab for Ocean Sciences, East Boothbay, ME, United States, (3)USGS Colorado Water Science Center Boulder, Boulder, CO, United States, (4)Michigan Technological University, Research Institute, Houghton, MI, United States, (5)Bowdoin College, Brunswick, ME, United States
Ongoing climate change is affecting the timing and amount of dissolved organic carbon (DOC) exported to the Gulf of Maine (GoM) through effects on hydrologic conditions. Climate warming in the northeast United States has resulted in decreases in snowfall amount and increases in the proportion of annual precipitation that falls as rain compared with snow. Warming has resulted in an increase in runoff during winter and earlier snowmelt and associated high spring flow. Increases in annual precipitation have resulted in increases in annual runoff. Increases in flashiness in some rivers have resulted in higher variability in daily runoff. DOC fluxes were estimated for water years 1950 through 2012 in eight rivers draining to the GoM that had long-term discharge data and data for DOC during all months of the year. These estimates used LOADEST to fit a seasonally-adjusted concentration - discharge relation. The adjusted maximum likelihood estimation (AMLE) method was used to estimate loads. One of several predefined regression models evaluated in LOADEST was selected based on the Akaike information criterion (AIC) for each river. This analysis assumed stationarity in the concentration - discharge relations. The proportion of total annual DOC exported during winter has increased. The proportion of DOC exported during March and April has also increased and the proportion exported during May has decreased in association with earlier snowmelt runoff and earlier recession to summer low flow. The total annual DOC exported by these rivers increased significantly from 1950 to 2012. The increase in flashiness has increased daily variability in DOC export in some rivers. Changes in the timing and amount of DOC exported to the near coastal ocean may influence marine biogeochemistry including the development of nuisance and harmful algal blooms, carbon sequestration, and the interpretation of satellite-derived ocean color. Terrestrially derived DOC exported to the marine environment could decrease phytoplankton productivity through light attenuation.