Century-Long Increasing Trend and Variability of Dissolved Organic Carbon Export from the Mississippi River Basin Driven by Natural and Anthropogenic Forcing

Authors

Wei Ren, University of KentuckyFollow
Hanqin Tian, Auburn University
Wei-Jun Cai, University of Delaware
Steven E. Lohrenz, University of Massachusetts - Dartmouth
Charles S. Hopkinson, University of Georgia
Wei-Jen Huang, National Sun Yat-sen University, Taiwan
Jia Yang, Auburn University
Bo Tao, University of KentuckyFollow
Shufen Pan, Auburn University
Ruoying He, North Carolina State University

Abstract

There has been considerable debate as to how natural forcing and anthropogenic activities alter the timing and magnitude of the delivery of dissolved organic carbon (DOC) to the coastal ocean, which has ramifications for the ocean carbon budget, land-ocean interactions, and coastal life. Here we present an analysis of DOC export from the Mississippi River to the Gulf of Mexico during 1901–2010 as influenced by changes in climate, land use and management practices, atmospheric CO₂, and nitrogen deposition, through the integration of observational data with a coupled hydrologic/biogeochemical land model. Model simulations show that DOC export in the 2000s increased more than 40% since the 1900s. For the recent three decades (1981–2010), however, our simulated DOC export did not show a significant increasing trend, which is consistent with observations by U.S. Geological Survey. Our factorial analyses suggest that land use and land cover change, including land management practices (LMPs: i.e., fertilization, irrigation, tillage, etc.), were the dominant contributors to the century-scale trend of rising total riverine DOC export, followed by changes in atmospheric CO₂, nitrogen deposition, and climate. Decadal and interannual variations of DOC export were largely attributed to year-to-year climatic variability and extreme flooding events, which have been exacerbated by human activity. LMPs show incremental contributions to DOC increase since the 1960s, indicating the importance of sustainable agricultural practices in coping with future environmental changes such as extreme flooding events. Compared to the observational-based estimate, the modeled DOC export was 20% higher, while DOC concentrations were slightly lower. Further refinements in model structure and input data sets should enable reductions in uncertainties in our prediction of century-long trends in DOC.

Document Type

Article

Publication Date

9-5-2016

Notes/Citation Information

Published in Global Biogeochemical Cycles, v. 30, issue 9, p. 1288-1299.

©2016. American Geophysical Union. All Rights Reserved.

The copyright holders have granted the permission for posting the article here.

Digital Object Identifier (DOI)

https://doi.org/10.1002/2016GB005395

Funding Information

This study has been supported by NASA Interdisciplinary Science Programs (NNX10AU06G) and Carbon System Monitoring Program (NX14AO73G and NNX12AP84G). Partial support was also provided by NSF OCE-1238212 (CSH), NSF OCE-1237140 (CSH & WJC). CSH is an affiliated member of the UGA RBC, CICR and UGAMI (Contr#1053).

Repository Citation

Ren, Wei; Tian, Hanqin; Cai, Wei-Jun; Lohrenz, Steven E.; Hopkinson, Charles S.; Huang, Wei-Jen; Yang, Jia; Tao, Bo; Pan, Shufen; and He, Ruoying, "Century-Long Increasing Trend and Variability of Dissolved Organic Carbon Export from the Mississippi River Basin Driven by Natural and Anthropogenic Forcing" (2016). Plant and Soil Sciences Faculty Publications. 82.
https://uknowledge.uky.edu/pss_facpub/82