no news are Bad News
ONE MILE OF ICE TO MELT on Ice Melt: This Time Greenland
May 19, 2014
Illustration
showing newly revealed topography of subsealevel glacial channels in
Greenland, from the new Nature Geoscience paper by Morlighem, Rignot et
al Note below sea level “bowl” in the interior.
The bed topography beneath the Greenland ice sheet controls the flow of ice and its discharge into the ocean. Outlet glaciers move through a set of narrow valleys whose detailed geometry is poorly known, especially along the southern coasts. As a result, the contribution of the Greenland ice sheet and its glaciers to sea-level change in the coming century is uncertain. Here, we combine sparse ice-thickness data derived from airborne radar soundings with satellite- derived high-resolution ice motion data through a mass conservation optimization scheme . We infer ice thickness and bed topography along the entire periphery of the Greenland ice sheet at an unprecedented level of spatial detail and precision. We detect widespread ice-covered valleys that extend significantly deeper below sea level and farther inland than previously thought. Our findings imply that the outlet glaciers of Greenland, and the ice sheet as a whole, are probably more vulnerable to ocean thermal forcing and peripheral thinning than inferred previously from existing numerical ice-sheet models.Basic issue – Greenland is essentially a ring of mountains surrounding a bowl of ice.
Where fingers of the sea can reach in beneath the ice and get to the soft underbelly, glacial outflow can proceed really quickly.....NO BECAUSE IS SOME ISOSTATIC COMPENSATION
AND STRESS RELATED FAULTS THAT GOING ON AND OFF
New paper indicates there’s a lot more fingers than we thought, and longer.
This possibility was discussed in my video last year by the ever-prescient Dr.Mike MacCracken.
Greenland’s icy reaches are far more vulnerable to warm ocean waters from climate change than had been thought, according to new research by UC Irvine and NASA glaciologists. The work, published today in Nature Geoscience, shows previously uncharted deep valleys stretching for dozens of miles under the Greenland Ice Sheet.
The bedrock canyons sit well below sea level, meaning that as subtropical Atlantic waters hit the fronts of hundreds of glaciers,THEY GOING TO GO FROM WARM SUBTROPICAL TO 4ºC
AND SINK....AND WATER COLD AND WITH LOW DENSITY GOING TO APPEAR IN GREAT AMOUNTS AT THE SURFACE... those edges will erode much further than had been assumed and release far greater amounts of water.
Ice melt from the subcontinent has already
accelerated as warmer marine currents have migrated north, but older
models predicted that once higher ground was reached in a few years, the
ocean-induced melting would halt. Greenland’s frozen mass would stop
shrinking, and its effect on higher sea waters would be curtailed.
“That turns out to be incorrect. The glaciers
of Greenland are likely to retreat faster and farther inland than
anticipated – and for much longer – according to this very different
topography we’ve discovered beneath the ice,” said lead author Mathieu
Morlighem, a UCI associate project scientist. “This has major
implications, because the glacier melt will contribute much more to
rising seas around the globe.”
To obtain the results, Morlighem developed a
breakthrough method that for the first time offers a comprehensive view
of Greenland’s entire periphery. It’s nearly impossible to accurately
survey at ground level the subcontinent’s rugged, rocky subsurface,
which descends as much as 3 miles beneath the thick ice cap.
Since the 1970s, limited ice thickness data
has been collected via radar pinging of the boundary between the ice and
the bedrock. Along the coastline, though, rough surface ice and pockets
of water cluttered the radar sounding, so large swaths of the bed
remained invisible.
Measurements of Greenland’s topography have
tripled since 2009, thanks to NASA Operation IceBridge flights. But
Morlighem quickly realized that while that data provided a fuller
picture than had the earlier radar readings, there were still major gaps
between the flight lines.
To reveal the full subterranean landscape, he
designed a novel “mass conservation algorithm” that combined the
previous ice thickness measurements with information on the velocity and
direction of its movement and estimates of snowfall and surface melt.
The difference was spectacular. What appeared
to be shallow glaciers at the very edges of Greenland are actually long,
deep fingers stretching more than 100 kilometers (almost 65 miles)
inland.
“We anticipate that these results will have a profound and transforming impact on computer models of ice sheet evolution in Greenland in a warming climate,” the researchers conclude.
“Operation IceBridge vastly improved our
knowledge of bed topography beneath the Greenland Ice Sheet,” said
co-author Eric Rignot of UC Irvine and NASA’s Jet Propulsion Laboratory.
“This new study takes a quantum leap at filling the remaining, critical
data gaps on the map.”
The team also reported stark new findings last
week on accelerated glacial melt in West Antarctica. Together, the
papers “suggest that the globe’s sheets will contribute far more to sea level rise than current projections show,” Rignot said.
BOMB THE Large-scale fractures related to inception of the
Yellowstone hotspot AND STOP THE MELTING
Jonathan M.G. Glen
U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA, and Berkeley
Geochronology Center, 2455 Ridge Road, Berkeley, California 94709, USA
David A. Ponce
U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA
ABSTRACT
During middle Miocene time, western North America was subject to flood-basalt vol-
canism, dike-swarm injection, and broad-scale fracturing and folding of the crust. We
propose a simple model to account for these events and for a regional pattern of geologic
and geophysical features. Aeromagnetic maps reveal some of the most important elements
of this pattern, which are several narrow, arcuate anomalies, here referred to as the
Northern Nevada rifts. These rifts extend hundreds of kilometers across Nevada and are
likely caused by highly magnetic, middle Miocene mafic dikes. With the aid of filtering
techniques, the anomalies can be traced into Oregon. Together with other geologic fea-
tures, such as fold axes, dike swarms, and faults, they produce a spoke-like pattern fanning
over 220
of arc that converges toward a point near the Oregon-Idaho border
A possible cause for this pattern is a point source of stress at the base of the crust related
to the formation of the Yellowstone hotspot. The spoke-like pattern, however, does not
persist at large distances from the emerging hotspot; several hundred kilometers to the
south, the Northern Nevada rifts deviate significantly (From a radial trend. We show
that a simple model—imposing a point source of stress at the base of the crust and a
regional stress field aligned with the presumed middle Miocene stress direction—fits the
observed fracture pattern. It thus accounts for both the radial pattern present near the
nascent hotspot and the far-field pattern due to regional stresses.
Keywords:
Yellowstone hotspot, Northern Nevada rifts, Snake River Plain, dike swarm, flood
basalts, Columbia River Plateau.
INTRODUCTION
Among the most striking geophysical fea-
tures of western North America (Figs. 1 and
2) are long and narrow positive magnetic
anomalies (collectively referred to here as
the Northern Nevada rifts
