Spatial and Temporal Variations in Eastern U.S. Hydrology: Responses to Global Climate Variability

Abstract

Coastal ecosystems are dependent on terrestrial freshwater export which is affected by both climate trends and natural climate variability. However, the relative role of these factors is not clear. Here, both climate trends and internal climate variabilities at different time scales are related to variations in terrestrial freshwater export into the eastern United States (U.S.) coastal region. For the recent 35‐year period, the intensified hydro‐meteorological processes (annual precipitation or evapotranspiration) may explain the observed streamflow variability in the northeast. However, in the southeast, streamflow is positively correlated with climate variability induced by the Pacific Ocean conditions (El Nino‐Southern Oscillation [ENSO] and Pacific Decadal Oscillation) rather than Atlantic Ocean conditions (Atlantic Multi‐decadal Oscillation and North Atlantic Oscillation). The centroid location for volume of terrestrial freshwater export integrated along the eastern U.S. has a positive temporal trend and is negatively correlated with ENSO conditions, suggesting the northward trend in freshwater export to U.S. eastern coast may be disturbed by the natural climate variability, especially ENSO conditions, i.e., the center of freshwater mass moves southward (northward) during El Nino (La Nina) years. The results indicate the spatial and temporal variations in freshwater export from the eastern U.S. are affected by both climate change and inter‐annual climate variability during the recent 35‐year period (1980‐2014).

Characterizing Precipitation Variability and Trends in the World’s Mediterranean-Climate Areas

“…Because multiannual cycles (e.g., ENSO) and events (e.g., long-term drought) have the potential to influence precipitation over periods greater than a decade [38,49], we distinguished those sites with between 30 and 40 years of quality-checked record from those with between 20 and 30 years of quality-checked record.…”

“…Research has indicated that climate and associated hydrologic processes (such as streamflow production) have already begun to change in some parts of the world, including significant downward trends in precipitation in parts of India [34] and New Zealand [35], as well as downward trends in dry-season streamflow and upward trends in peak streamflow in parts of the United States [36][37][38][39][40]. If temperate dry-summer climate zones are undergoing changes in climate variables-such as increased or decreased annual precipitation-these changes could already be causing shifts in ecological community composition and structure.…”

Multivariate Climate Field Reconstructions Using Tree Rings for the Northeastern United States

“…The majority of the AWC network is located less than 10 km from the coast, where climate is strongly influenced by Atlantic Ocean dynamics (B. I. Feng et al, 2016;Namias, 1967;Seager et al, 2012;Wettstein & Mearns, 2002). We find strong correlations with the temperature-sensitive network's EOF1 with local and cross basin Atlantic SSTs (Figure 4; Pearl et al, 2017).…”

“…Feng et al, 2016;Namias, 1967;Seager et al, 2012;Wettstein & Mearns, 2002). Feng et al, 2016;Namias, 1967;Seager et al, 2012;Wettstein & Mearns, 2002).…”

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“…Given that the southeastern United States is predicted to experience increases in drought frequency and intensity (Ficklin et al 2015;Feng et al 2016), efforts may be needed to protect sensitive wetland-associated species like N. floridana. Mitigating or managing drought effects is difficult, since droughts often span large spatial and temporal scales, and are unpredictable in timing and severity (Bond et al 2008).…”