Glacioisostasy and Lake-Level Change at Moosehead Lake, Maine

Abstract

Reconstructions of glacioisostatic rebound based on relative sea level in Maine and adjacent Canada do not agree well with existing geophysical models. In order to understand these discrepancies better, we investigated the lake-level history of 40-km-long Moosehead Lake in northwestern Maine. Glacioisostasy has affected the level of Moosehead Lake since deglaciation ca. 12,500 14C yr B.P. Lowstand features at the southeastern end and an abandoned outlet at the northwestern end of the lake indicate that the lake basin was tilted down to the northwest, toward the retreating ice sheet, by 0.7 m/km at 10,000 14C yr B.P. Water level then rose rapidly in the southeastern end of the lake, and the northwestern outlet was abandoned, indicating rapid relaxation of landscape tilt. Lowstand features at the northwestern end of the lake suggest that the lake basin was tilted to the southeast at ca. 8750 14C yr B.P., possibly as the result of a migrating isostatic forebulge. After 8000 14C yr B.P., water level at the southeastern end was again below present lake level and rose gradually thereafter. We found no evidence suggesting that postglacial climate change significantly affected lake level. The rebound history inferred from lake-level data is consistent with previous interpretations of nearby relative sea-level data, which indicate a significantly steeper and faster-moving ice-proximal depression and ice-distal forebulge than geophysical models predict.

Late Quaternary Relative Sea-Level Change on the West Coast of Newfoundland*

“…This rate compares favourably with other estimates for the west coast of Newfoundland based on salt-marsh and tidegauge data (50 km per ka; Daly, 2002) and the raised marine shell record (45 km per ka; Liverman, 1994), although the latter was predicated on forebulge migration between 13 000 and 7000 14 C BP (Liverman, 1994). This rate is also consistent with the rate of forebulge migration calculated between Moosehead Lake (Maine) and Québec City (Balco et al, 1998), but is somewhat lower than the 70-110 km per ka rate estimated for the Gulf of Maine (Barnhardt et al, 1995).…”

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

“…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).…”

Parallel climate and vegetation responses to the early Holocene collapse of the Laurentide Ice Sheet

“…Relatively large lakes, complicated by processes such as isostatic adjustment (e.g. Yu and Andrews, 1994;Balco et al, 1998) were not included, nor were complex sites where ecological or local hydrological processes may explain the record (e.g. Delcourt et al, 1983;Thorson and Webb, 1991).…”