The origin of the vertical motions of East Greenland is a long-standing
enigma. The area is characterized by a mountain chain >1000 km long,
wherein the high peaks (2.5-3.7 km elevation) reside above a relatively
thin crust (30-35 km). These mountains contain Mesozoic marine sediments
uplifted to 1.2 km during the tectonic quietness of the middle to late
Cenozoic. This uplifted area is cut by some of the world's biggest
fjords. Scoresbysund fjord is as wide as 60 km, and cuts 400 km into the
land and more than 4 km down from the peaks of the region. We test the
potential amount of regional uplift and subsidence caused by the fjords'
incision and associated deposition of sediments offshore. These tests
are based on modeling the erosion process backward in time. The fjords
are filled back to the summit surface while similar weights of sediments
are removed from the shelf. The model considers the isostatic response
of the lithosphere due to the loading and unloading of bedrock,
sediments, water, and ice. Our estimates show that an average of almost
1.2 km of bedrock was eroded in the region from the middle Cenozoic
summit surface. Most of the erosional products were deposited on the
continental shelf outside the mouth of the fjords. Our calculations
demonstrate that rocks in the central Fjord Mountains may be uplifted as
much as 1.1 km due to the erosional unloading and flexural isostatic
effects. Thus these effects should present a main part of the mechanisms
responsible for the Cenozoic uplift in central East Greenland. Because
the North Atlantic is rimmed by young glacially carved mountain chains,
the model may be applicable to other parts of the area.