Centennial‐to‐millennial hydrologic trends and variability along the North Atlantic Coast, USA, during the Holocene

Abstract

Geophysical and sedimentary records from five lakes in Massachusetts reveal regionally coherent hydrologic variability during the Holocene. All of the lakes have risen since~9.0 ka, but multicentury droughts after 5.6 ka repeatedly lowered their water levels. Quantified water level histories from the three best-studied lakes share >70% of their reconstructed variance. Four prominent low-water phases at 4.9-4.6, 4.2-3.9, 2.9-2.1, and 1.3-1.2 ka were synchronous across coastal lakes, even after accounting for age uncertainties. The droughts also affected sites up to~200 km inland, but water level changes at 5.6-4.9 ka appear out of phase between inland and coastal lakes. During the enhanced multicentury variability after~5.6 ka, droughts coincided with cooling in Greenland and may indicate circulation changes across the North Atlantic region. Overall, the records demonstrate that current water levels are exceptionally high and confirm the sensitivity of water resources in the northeast U.S. to climate change.

Climatic history of the northeastern United States during the past 3000 years

“…Several lake level reconstructions in the NE US are based on ground penetrating radar (GPR) and transects of multiple sediment cores from a lake margin (Newby et al, 2014;Pribyl and Shuman, 2014). This approach enables continuous reconstructions of shoreline advances and retreats through time that at least partly reflect changing hydroclimate (Digerfeldt, 1986).…”

“…This approach enables continuous reconstructions of shoreline advances and retreats through time that at least partly reflect changing hydroclimate (Digerfeldt, 1986). Factors such as isostasy and tectonics can influence large lakes (Balco et al, 1997(Balco et al, , 1998 but operate on scales greater than the small ponds that have been used to reconstruct regional hydrologic changes (Newby et al, 2014). Groundwater flow directly controls the water levels in many small ponds and lakes (Almendinger, 1993;Winter, 1999), but annual changes in precipitation and evaporation have strong regional impacts (Weider and Boutt, 2010).…”

“…Data reflecting hydroclimatic variability are more abundant in the NE US, coming from tree-rings (e.g., Cook andKrusic, 2004, 2008;Pederson et al, 2014), lake levels (e.g., Shuman et al, 2002), variations in lake chemistry (e.g., Li et al, 2007), shifts in diatoms (Boeff et al, 2016), and changes in testate amoeba composition from bog sediments (e.g., Booth et al, 2012). Such data show relatively wet conditions in the late versus the mid-Holocene (Digerfeldt et al, 1992;Almquist et al, 2001;Shuman et al, 2009) with increasing effective moisture towards present (Newby et al, 2014). Episodic drought and pluvial events, documented by a variety of proxies, are superimposed on the gradual trend towards increasing moisture (Pederson et al, 2005).…”

Millennial-to-centennial patterns and trends in the hydroclimate of North America over the past 2000 years

“…In the northeast U.S., where the greatest density of quantitative records exists, the lake-level and pollen records indicate an increase in annual effective precipitation of 25-50 mm, about 2-5% of mean annual precipitation in the region today, since the early part of the first millennium CE (Gajewski, 1988;Marsicek et al, 2013;Newby et al, 2014). Trends range from having magnitudes similar to those in northeast to no significant trends in pollen-inferred precipitation 25 reconstructions from the Great Lakes region (Gajewski, 1988;St.…”

“…One potential implication is that long-term trends (>100-1000 years) affected more of North America than is apparent from our dataset, but 20 some archives (e.g., detrended bog records) do not preserve such signals. Some records may act as stringent low-pass filters (e.g., sedimentary records of lake-level change; Newby et al, 2014), but others may be better suited to recording discrete events (e.g., bogs in the northeast U.S.; Booth et al, 2006). Furthermore, the climate signals were weak relative to our ability to reconstruct them.…”