Gravity from 60° N to the North Pole

Abstract

Three free-air gravity anomaly maps for the Arctic region north of 60°N are presented. The maps show the gravity field derived from mean values based on observed and predicted data, the field based on calculated satellite gravity data, and the residual gravity field derived by removing the satellite gravity field from the observed field. The satellite map shows regional gravity anomalies with widths of 1000 km or more. The residual anomaly map and the map compiled from observed and predicted data outline gravity anomalies with widths ranging from 100 km to 1000 km. The smaller wavelength of the latter provides information on the locations of anomalous sub-surface structures and major density - lithological variations within the crust and mantle. Gravity highs straddle the polar continental breaks of North America, Svalbard, Scandinavia, and Greenland and are present over submarine ridges (Lomonosov, Alpha and Mid-Atlantic) and plateaus (Chukchi, Morris Jesup and Yermak). Many of these highs are simply a reflection of positive sea-bottom topography, but those along the continental margins are believed to indicate regions of uncompensated sediments. Extensive gravity lows which correlate with regions of generally high relief, such as northern Greenland and southeastern Alaska and adjacent Yukon, probably indicate that these regions are overcompensated by either a thicker crust or less dense crust and mantle than normal. Gravity lows over the Canada, Makarov, and Fram Basins may be indicative of the thick low density sediments present there. Over central Greenland a belt of steep gradients separates a relatively negative region of anomalies to the north from a more positive gravity field to the south and suggests significant changes in either the thickness of the crust or in the lithologies and densities of the crust and mantle in this region.