Tag Archives: glaciers

Geothermal heat flux a significant contributor to Greenland Ice melting

Irina M. Artemieva. Lithosphere thermal thickness and geothermal heat flux in Greenland from a new thermal isostasy method. Earth-Science Reviews, Volume 188, January 2019, Pages 469-481. https://doi.org/10.1016/j.earscirev.2018.10.015

Lithosphere thermal structure in Greenland is poorly known and models based on seismic and magnetic data are inconsistent, while growing awareness in the fate of the ice sheet in Greenland requires reliable constraints on geothermal heat flux (GHF) from the Earth’s interior in the region where conventional heat flux measurements are nearly absent. The lithosphere structure of Greenland remains controversial, while its geological evolution is constrained by direct observations in the narrow ice-free zone along the coasts. The effect of the Iceland hotspot on the lithosphere structure is also debated.

Here I describe a new thermal isostasy method which I use to calculate upper mantle temperature anomalies, lithosphere thickness, and GHF in Greenland from seismic data on the Moho depth, topography and ice thickness. To verify the model results, the predicted GHF values are compared to available measurements and show a good agreement. Thick (200–270 km) cratonic lithosphere of SW Greenland with GHF of ca. 40 mW/m2 thins to 180–190 km towards central Greenland without a clear boundary between the Archean and Proterozoic blocks, and the deepest lithosphere keel is observed beneath the largest kimberlite province in West Greenland. The NW-SE belt with an anomalously thin (100–120 km) lithosphere and GHF of 60–70 mW/m2 crosses north-central Greenland from coast to coast and it may mark the Iceland hotspot track. In East Greenland this anomalous belt merges with a strong GHF anomaly of >100 mW/m2 in the Fjordland region. The anomaly is associated with a strong lithosphere thinning, possibly to the Moho, that requires advective heat transfer such as above active magma chambers, which would accelerate ice basal melting. The anomaly may extend 500 km inland with possibly a significant contribution of ice melt to the ice-drainage system of Greenland.

Additional papers here.

Glacier National Park disproves glacier melting predictions

“Titled “Glacier National Park Quietly Removes Its ‘Gone by 2020′ Signs,” Roots’ article describes a scramble by federal park officials to hide or replace evidence of now-embarrassingly inaccurate and alarmist predictions in a manner that skirts public attention.” click here

Growing glacier disproves Washington Post article “climate change” claim

Greenland glacier not following climate modeler’s predictions

“Greenland’s most famous glacier has grown nearly 10km over the past seven years. click here

Has Himalayan glacier melting doubled?

“A newly comprehensive study shows that melting of Himalayan glaciers caused by rising temperatures has accelerated dramatically since the start of the 21st century,” claims a Ph.D. candidate at Columbia University’s Lamont-Doherty Earth Observatory. Willis Eschenbach shares his thoughtsclick here

Greenland glaciers either stable or growing

“In 2018, 26 of Greenland’s 47 largest glaciers were either stable or grew in size. Overall, the 47 glaciers advanced by +4.1  km² during 2018.  Of the 6 largest glaciers, 4 grew while 2 retreated. Since 2012, ice loss has been “minor” to “modest” due to the dramatic melting slowdown. Summer average temperatures for 2018 were lower than the 2008-2018 average by more than one standard deviation. Since 2000, the extent of the non-snow-covered areas of Greenland has increased by 500 km² per year.” click here

Greenland Ice sheet growing since 2016

Ala Khazendar, et al. Interruption of two decades of Jakobshavn Isbrae acceleration and thinning as regional ocean cools. Nature Geoscience. (here)

Jakobshavn Isbrae has been the single largest source of mass loss from the Greenland Ice Sheet over the last 20 years. During that time, it has been retreating, accelerating and thinning. Here we use airborne altimetry and satellite imagery to show that since 2016 Jakobshavn has been re-advancing, slowing and thickening. We link these changes to concurrent cooling of ocean waters in Disko Bay that spill over into Ilulissat Icefjord. Ocean temperatures in the bay’s upper 250 m have cooled to levels not seen since the mid 1980s. Observations and modelling trace the origins of this cooling to anomalous wintertime heat loss in the boundary current that circulates around the southern half of Greenland. Longer time series of ocean temperature, subglacial discharge and glacier variability strongly suggest that ocean-induced melting at the front has continued to influence glacier dynamics after the disintegration of its floating tongue in 2003. We conclude that projections of Jakobshavn’s future contribution to sea-level rise that are based on glacier geometry are insufficient, and that accounting for external forcing is indispensable.