Tag Archives: glaciers

Alaskan glaciers have not retreated, but many have advanced

R. W. McNabb R. Hock. Alaska tidewater glacier terminus positions, 1948–2012. Journal of Geophysical Research: Earth Surface, Volume 119, Issue 2
https://doi.org/10.1002/2013JF002915

A significant portion of the world’s glacier ice drains through tidewater outlets, though much remains unknown about the response to recent climate change of tidewater glaciers. We present a 64 year record of length change for 50 Alaska tidewater glaciers. We use U.S. Geological Survey topographic maps to provide a base length for glaciers before 1970. Using all available cloud‐free Landsat images, we manually digitize calving front outlines for each glacier between 1972 and 2012, resulting in a total of more than 10,000 outlines. Tidewater glacier lengths vary seasonally; focusing on the 36 glaciers terminating in tidewater throughout the study period, we find a mean (± standard deviation) seasonal variation of 60± 85 m a−1. We use these oscillations to determine the significance of interannual changes in glacier length. All 36 glaciers underwent at least one period (≥1 year) of significant advance or retreat; 28 glaciers underwent at least one period of both significant advance and retreat. Over the entire period 1948–2012, 24 of these glaciers retreated a total (± uncertainty) of 107.95±0.29 km, 11 advanced a total of 7.71±0.20, and one (Chenega Glacier) did not change significantly. Retreats and advances are highly variable in time; several glaciers underwent rapid, short‐term retreats of a few years duration. These retreats occurred after large changes in summer sea surface temperature anomalies; further study is needed to determine what triggered these retreats. No coherent regional behavior signal is apparent in the length record, although two subregions show a coherence similar to recent observations in Greenland.

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