Melting at the base of the Greenland ice sheet explained by Iceland hotspot history

Abstract

GF is high and melt water is present under ice cover [11][12] Greenland to explain the origin of the observed melting beneath the ice cover (Figure 1). This are controlled by a combination of GF and non-GF influences, we build our calibration 137 strategy on estimating GF required to reproduce the observed thawed basal ice conditions, 138 discounting basal ice melt rates as a proxy for GF. This has the effect that GF estimates will 139 likely be biased downwards where basal melt is rapid; nevertheless, our strategy is 140 sufficiently effective to separate out the signal of a strong and spatially extensive geothermal 141 anomaly beneath the GIS and provides a hard lower bound for GF values at the observed 142 basal melt locations. 143The anomalous GF zone lies in the area with the highest density of direct measurements. 150One potential cause of elevated GF is illustrated by seismic data that link our west-to-east GF 151anomaly with a zone of low-seismic-velocity mantle, a "negative anomaly", beneath Iceland 6- Greenland may be the expression of Iceland hotspot history. The geothermal anomaly 237 provides evidence for a more northerly hotspot track than previously proposed and will offer 238 a useful test for existing paleoreconstructions of absolute plate motion. This study advocates 239 a previously undocumented strong coupling between Greenland's present-day ice dynamics, 240 subglacial hydrology, and the remote tectonothermal history of the North Atlantic region.

Paleofluvial and subglacial channel networks beneath Humboldt Glacier, Greenland

“…Extensive portions of northern Greenland, including the Humboldt Glacier catchment, have a basal temperature equal to the pressure-melting temperature (Oswald and Gogineni, 2012;MacGregor et al, 2016). These warm bed conditions associated with the Humboldt catchment are modeled to extend >100 km inland and originate from a geothermal anomaly (Rogozhina et al, 2016). Thus, the long-term and large-scale pattern of subglacial channel incision under Humboldt Glacier is consistent with the regional tectonothermal history of northern Greenland (Rogozhina et al, 2016).…”

A constraint upon the basal water distribution and basal thermal state of the Greenland Ice Sheet from radar bed-echoes

“…Recent analyses imply that much of the spatial variation in GHF beneath the northern GrIS can be explained by Greenland's passage over the Iceland mantle plume between roughly 35 and 80 million years ago (Rogozhina et al, 2016;Martos et al, In revision). The magnetic GHF map in Fig.…”

“…Experiments with 3D models to reconstruct the full ice temperature history over the last glacial cycle(s) can constrain the minimum GHF required to produce basal melting at the predicted basal water locations (Huybrechts, 1996). Other studies include investigating the sensitivity of ice-sheet dynamics to the thermal boundary condi-515 tion (Seroussi et al, 2013) or basal lubrication (Shannon et al, 2013), and thermal models of the underlying lithosphere (Rogozhina et al, 2016).…”

“…van de Wal et al (2008)), basal melting due to geothermal heat (e.g. Dahl-Jensen et al (2003); Rogozhina et al (2016)), frictional and shear heating (e.g. van der Veen (2013)), and transport processes (surface, englacial and subglacial) which 30 redistribute water (e.g.…”

“…(37-50 mW m −2 ) that are typically associated with non-altered ancient continental crust (Artemieva, 2006;Rogozhina et al, 2016 In Fig. 8 the basal water predictions are underlain by three different GHF models: the seismic model by Shapiro and Ritzwoller (2004), and two models derived from magnetic anomalies by In Fig.…”