Episodic riverine influence on surface DIC in the coastal Gulf of Maine |
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Authors: | Joseph Salisbury Douglas Vandemark Christopher Hunt Janet Campbell Bror Jonsson Amala Mahadevan Wade McGillis Huijie Xue |
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Institution: | 1. Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03825, USA;2. Department of Earth Sciences, Boston University, Boston, MA 02215, USA;3. Lamont–Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA;4. School of Marine Science, University of Maine, Orono, ME 04469, USA |
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Abstract: | Anomalously high precipitation and river discharge during the spring of 2005 caused considerable freshening and depletion of dissolved inorganic carbon (DIC) in surface waters along the coastal Gulf of Maine. Surface pCO2 and total alkalinity (TA) were monitored by repeated underway sampling of a cross-shelf transect in the western Gulf of Maine (GOM) during 2004–05 to examine how riverine fluxes, mixing, and subsequent biological activity exert control on surface DIC in this region. Most of the variability in surface DIC concentration was attributable to mixing of low DIC river water with higher DIC, saline GOM waters, but net biological uptake of DIC was significant especially during the spring and summer seasons. The extent and persistence of the coastal freshwater intrusion exerted considerable influence on net carbon dynamics. Integrated over the 10-m surface layer of our study region (∼5 × 104 km2), net biological DIC uptake was 0.48 × 108 mol C during April–July of 2004 compared to 1.33 × 108 mol C during April–July of 2005. We found the temporal signature and magnitude of DIC cycling to be different in adjacent plume-influenced and non-plume regions. Extreme events such as the freshwater anomaly observed in 2005 will affect mean estimates of coastal carbon fluxes, thus budgets based on short time series of observations may be skewed and should be viewed with caution. |
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Keywords: | Coastal Dissolved inorganic carbon CO2 Air&ndash sea exchange Land&ndash Ocean |
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