19 Ice sheets, glaciers, and landscapes, oh my!
Glaciers and ice sheets shaped the landscape of the Northeast. Ice continues to shape the landscape of alpine and polar regions. We welcome submissions on glaciers & ice sheets of any size, shape, age, and location.
Monday, 23 March 2026
8:00 AM - 12:00 PM
CCC, Room 26
ESTIMATE OF GLACIAL MELTWATER CONTRIBUTION TO GLACIAL LAKE HITCHCOCK DURING LIS RECESSION (15.5-14 KA) IN THE CONNECTICUT VALLEY OF NEW HAMPSHIRE AND VERMONT
Paper number: 19-5
Program: Technical Sessions
Time: 9:25 AM – 9:45 AM
Authors
Abstract
Meltwater generated during Connecticut Valley (CV) LIS recession (15.5-14 ka) has implications for varve deposition (Lake Hitchcock) and LIS climate response. A meltwater estimate is inspired by studies of modern Greenland Ice Sheet (GIS) mass loss contributions to global sea level rise tabulated from ice sheet profile changes and mass loss measurements (e.g., Box etal., 2022). The CV model infers meltwater discharge by calculating combined mass losses (across 80-km width) of: 1) the annual retreat of an assumed-constant, ablation area ice sheet profile (1-bar basal shear stress) plus 2) the ice mass that annually flows through the glacier’s equilibrium line (EL) into the ablation area. A southwestern GIS sector (67ºN) is chosen as an analog where recession is without the influence of high velocity ice streams that penetrate deep into the ice sheet and calve in fjords. The GIS EL is100 km from the margin (Noël etal., 2021) with average ice thickness of 1500 m (Gaba, 2011) and average velocity of 50-300 m/yr (Starr, 2012). CV ice was active and flowing on a wet bed as indicated by streamlined topography (LiDAR imagery), century-scale readvances, and lobate marginal striation patterns. Using Greenland parameters, a CV EL cross-sectional area (thickness x width) is 1.2x108m2. Annual meltwater discharges were calculated using Greenland EL velocities and CV varve-based ice recession rates of 50-300 m/yr (Ridge etal., 2012). A conservative average EL ice velocity of 100 m/yr and recession rates of 100-300 m/yr yielded meltwater discharges of 21.5-42.9 billion m3/yr (water equivalents), while the average annual discharge of the Connecticut River (since 1943) at N.Walpole, NH is 8.75 billion m3/yr (24.0 million m3/day). Study of summer layers in thick ice-proximal varves in the northeastern US reveal 90-140 uniform diurnal rhythmic units that provide an estimate of days in the melt season. If meltwater discharge is restricted to a 120-day melt season, discharges (100 m/yr EL flow, 100-300 m/yr recession) would be 177-353 million m3/day!! During CV LIS advance (~28-35 ka), ablation area profile changes were positive. If ice advanced at 50 m/yr (~200 km, 4 kyr), EL flow would be at least 125 m/yr to generate the modern N.Walpole Connecticut River discharge.
Geological Society of America Abstracts with Programs. Vol. 58, No. 2
doi: 10.1130/abs/2026NE-411233
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