Climate signal analysis Dr. Adrian B. Burd University of Georgia

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

adrianb@uga.edu http://www.marsci.uga.edu/directory/adrian-burd https://orcid.org/0000-0001-6345-8770 Georgia Coastal Ecosystems LTER Project

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

gcelter@uga.edu https://gce-lter.marsci.uga.edu/ Dr. Adrian B. Burd University of Georgia

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

adrianb@uga.edu http://www.marsci.uga.edu/directory/adrian-burd https://orcid.org/0000-0001-6345-8770 Principal investigator 2007-01-01 Joan E. Sheldon University of Georgia

Dept. of Marine Sciences University of Georgia Athens Georgia 30602-3636 USA

jsheldon@uga.edu https://orcid.org/0000-0002-6409-9500 Research professional 2007-01-01 2026

A. Burd (UGA) and J. Sheldon (UGA) are evaluating variability in freshwater delivery to the GCE domain in relation to various climate indices: the Southern Oscillation Index (SOI), the North Atlantic Oscillation (NAO) and the Bermuda High Index (BHI). They compared monthly standardized anomalies of river discharge and climate indices to multi-decadal time series of Altamaha watershed precipitation. They used empirical orthogonal function (EOF) analysis to describe the precipitation patterns at 7-13 stations. The first EOF mode (65% of the variance) was spatially uniform with temporal variability at the monthly scale. The second mode (11% of the variance) showed a spatial gradient along the long axis of the watershed (NW-SE) whereas the third mode (6% of the variance) showed an onshore-offshore pattern with higher variability during June-September. There were no consistent relationships between NAO and precipitation. The SOI showed correlations with discharge and weak correlations with modes 1 and 2 of the precipitation. The BHI is correlated with May-January discharge with a 0-1 month lag, and is also strongly correlated with EOF mode 1 of precipitation.

Linear correlations (Pearson r) between climate indices and other variables were generally weak to moderate. Non-uniform lags provided the highest correlations. The BHI is moderate/strongly correlated with the precipitation EOF 1 time series from Feb-Dec (strongest May-Nov) at lag 0 but has inconsistent correlations with EOF 2. BHI is correlated most strongly with June-Jan discharge with a 0-1 month lag. The May-Dec SOI is weakly correlated with the precipitation EOF 1 time series in the following Nov-Dec while the Sep-Feb SOI is correlated with the EOF 2 time series in Jan-Mar. SOI correlations with river discharge resemble those of precipitation EOF 2 more than EOF 1. Relationships between precipitation and two NAO indices were sporadic and inconsistent.

Question 1: What are the long-term patterns of environmental forcing to the coastal zone? (more information)

precipitation LTER NSF Altamaha River Georgia GCE Bermuda High Index climate discharge North Atlantic Oscillation Overall geographic extent of the research project -81.759763 -81.119291 31.771190 30.892711 2007-01-01 2012-11-01

National Science Foundation grant number OCE-0620959

estuary marsh complex Central Georgia Coast - Central Georgia coastal region from the South Newport River (northern extent) to the Satilla River (southern extent), and from the outer banks of the barrier islands (eastern extent) to approximately 35km inland (western extent) -81.759763 -81.119291 31.771190 30.892711 Altamaha River - Altamaha River transect used for GCE quarterly hydrographic monitoring surveys. Nominal profiling stations are defined every 2km from -4km to 40km (relative to station 0km at the line of demarcation), based on an estimated Thalweg line running up the main river channel. -81.582311 -81.237936 31.401403 31.296034 Sheldon, J.E. and Burd, A.B. 2014. Alternating Effects of Climate Drivers on Altamaha River Discharge to Coastal Georgia, USA. Estuaries and Coasts. 37:772–788. (DOI: 10.1007/s12237-013-9715-z) http://link.springer.com/article/10.1007/s12237-013-9715-z/fulltext.html Sheldon, J.E. and Burd, A.B. 2008. Poster: Seasonal effects of the Southern Oscillation and Bermuda High on freshwater delivery to the central Georgia coast. GCE-LTER 2008 Annual Meeting, March 14-15, 2008, Athens, Georgia. http://gce-lter.marsci.uga.edu/public/files/pubs/SheldonBurdClimateSignalsPoster_2008.pdf Sheldon, J.E. and Burd, A.B. 2007. Poster: Detecting climate signals in river discharge and precipitation data for the central Georgia coast. 2007 AERS/SEERS Meeting, March 15-17, 2007, Pine Knoll Shores, NC. http://gce-lter.marsci.uga.edu/public/files/pubs/JSheldon_SEERS_Poster_2007.ppt Sheldon, J.E. and Burd, A.B. 2007. Presentation: Seasonal Effects of the Southern Oscillation and Bermuda High on Freshwater Delivery to Coastal Georgia, U.S.A. Estuarine Research Federation 2007 Annual Meeting, 4-8 November 2007, Providence, Rhode Island. Time series of the Bermuda High Index and precipitation at Athens, GA. https://gce-lter.marsci.uga.edu/public/resources/projects/Table1AlberQ1.jpg