Sediment loading in Fennoscandia during the last glacial cycle

Abstract

Models for postglacial rebound, or Glacial Isostatic Adjustment (GIA) routinely include the effects of meltwater redistribution and changes in topography and coastlines. Since the sediment transport related to the dynamics of ice sheets may be comparable to that of sea level rise in terms of surface pressure, the loading effect of sediment deposition could 10 cause measurable ongoing viscous readjustment. Here we study the loading effect of glacial induced sediment redistribution (GISR) related to the Weichselian ice sheet in Fennoscandia and the Barents Sea. The surface loading effect and its effect on the gravitational potential is modelled by including changes in sediment thickness in the sea level equation following the method of Dalca et al. (2013). Sediment displacement estimates are estimated in two different ways: (i) from a compilation of studies on smaller features: through mouth fans, large scale failure and basin flux and (ii) from output of a coupled ice-15 sediment model. To account for uncertainty in Earth's rheology three viscosity profiles are used.It is found that sediment transport can lead to changes in relative sea level of at most several meters with the largest effect occurring earlier in the deglaciation. This magnitude is below the error level of most of the relative sea level data because data are sparse and errors are larger for older data. The maximum effect on present-day uplift rates is a few tenths of mm yr -1 , which is around the measurement error of long-term GPS monitoring networks. The maximum effect on present-day 20 gravity rates as measured by the GRACE satellite mission is up to tenths of μGal yr -1 , which is larger than the measurement error. Since GISR causes systematic uplift in most mainland Scandinavia, including GISR in GIA models would improve interpretation of GPS and GRACE observations there.