IMPLICATIONS FOR GLACIAL ISOSTATIC ADJUSTMENT MODELS AND CURRENT RATES OF SEA-LEVEL CHANGE

• Main Author: Simon E. Engelhart
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Ice Sheet
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.649.9129

This study develops the first database of Holocene sea-level index points for the U.S. Atlantic coast using a standardized methodology. The database will help further understanding of the temporal and spatial variability in relative sea-level (RSL) rise, provide constraints on geophysical models and document ongoing crustal movements due to Glacial Isostatic Adjustment (GIA). I sub-divided the U.S. Atlantic coast into 16 areas based on distance from the center of the Laurentide Ice Sheet. Rates of RSL change were highest during the early Holocene and have been decreasing over time, due to the continued relaxation response of the Earth’s mantle to GIA and the reduction of ice equivalent meltwater input around 7 ka. The maximum rate of RSL rise (c. 20 m since 8 ka) occurred in New Jersey and Delaware, which is subject to the greatest forebulge collapse. The rates of early Holocene (8 to 4 ka) rise were 3- 5.5 mm a-1. I employed basal peat index points, which are subject to minimal compaction, to constrain models of GIA. I demonstrated that the current ICE-5G/6G VM5a models cannot provide a unique solution to the observations of RSL during the Holocene. I reduced the viscosity of the upper mantle by 50%, removing the discrepancy between the observations and predictions along the mid-Atlantic coastline. However, misfits still remain in Maine, northern Massachusetts and the Carolinas. Late Holocene (4 ka to present) RSL data are a proxy for crustal