The
Resilient Earth

Science, Global Warming and the Fate of
Humanity

About
Us

Resilient Earth Store

Resilient Earth
Press

Home

Crank of the
Week

Monthly Archive

Papers
& References

The
Real Problem

The Blogosphere

Glossary

Suggested
Reading

TRE Wall
Papers

Privacy
Statement

Contact Us

User login

Log in using OpenID:

What is
OpenID?

Username:
*

Password:
*

Log in using OpenID

Cancel OpenID
login

Create new
account

Request new
password

Search This Site

Search this site:

Navigation

Popular content

Recent
posts

Feed
aggregator

Primary links

About
Us

Resilient Earth
Store

Resilient
Earth Press

Home

Crude Oil Price

Recent blog posts

True
Alternative Energy: The Power Of Thorium

Guest
Editorial – An Interview With Energy Security Expert Michael
Levi

Phishing
Site Warning!

New
Ice Surveys Finds Slower Ice-sheet Melting

IPCC
Gets It Backwards, Drought Causes Warming

Secrets
Of The Climate Modeling Mystics

Parker's
Folly, Doug L. Hoffman's Science Fiction Adventure, Now Available In
Trade Paperback

Orbital
Climate Cycles Reaffirmed, Classical Statistics Denied

Scientifically
Ignorant, Tabloid "Climatologists" Blame Sandy On Climate
Change

New
Global Energy Balance Data Shows Climate Models Profoundly
Uncertain

more

The Latest Resilient Earth Poll

Which Resilient Earth theme is best?:

New light theme (new default)

Old dark theme (old default)

Other links

Crank of the
Week

Monthly Archive

Papers
& References

The
Real Problem

The Blogosphere

Challenging Climate

Climate Change
Dispatch

Climate Debate Daily

Climate Depot

Climate Realists

Climate Research News

Climate Science

CO2 Science

Energywise

Go Nuclear!

ICECAP

International
Climate Science

JoNova

JunkScience.com

Next Grand
Minimum

NIPCC

Nuclear Street

OilPrice.com

Omniclimate

Popular
Techonolog.net

Science & Public
Policy

Skeptic's
Corner

Watts Up With That?

World Climate
Report

World Nuclear
News

Glossary

Suggested
Reading

TRE Wall
Papers

Privacy
Statement

Contact
Us

Who's online

There are currently 0 users and 31
guests online.

Home »
Blogs » Doug L.
Hoffman's blog

Antarctica Gains Ice From The Bottom Up

Scientists
have always thought that the vast majority of ice contained in the
Antarctic ice cap was formed from frozen precipitation. Recent research
has revealed that this is not totally correct. Over a large fraction of
East Antarctica, the deepest part of the ice sheet contains ice that did
not originate as surface snow but developed when subglacial meltwater was
frozen onto the underside of the ice sheet. The amount of ice involved is
much larger than the estimated volume of Antarctic subglacial lakes and
may even exceed the volume of all glaciers on Earth outside of the two
polar ice sheets. Current computer models predict that subglacial water
escapes toward the ocean. These new findings indicate that water from
areas of basal melting actually migrate to areas of basal freezing,
something not accounted for by current ice sheet models. To scientists'
surprise, the East Antarctic Ice Sheet is getting thicker from the bottom
up.

According to a Science report published online
March 3, 2011, by Robin E. Bell et al., little is known about
processes at the base of the ice sheets. In “Widespread
Persistent Thickening of the East Antarctic Ice Sheet by Freezing from the
Base,” researchers report that, although the surface accumulation of
snow remains the primary mechanism for ice sheet growth, beneath the
research site known as Dome A, 24% of the base by area is frozen-on ice.
In some places, up to half of the ice thickness has been added from below.
The unexpected thickness of these bottom layers of ice was detected using
radar imaging during the International Polar Year 2007–2009.

The exact mechanisms for the formation of this refrozen
ice depends on the location. According to Bell et al., the
freeze-on at valley heads is primarily the result of conductive cooling
over static bodies of water. Along the valley walls, ice is primarily the
result of the hydrologic potential forcing water up steep valley slopes.
But these processes are not mutually exclusive: individual packages of
frozen-on ice could well have been produced by a combination of the two
mechanisms. The authors speculate that the creation of bottom ice is
widespread and has been going on since the beginning of persistent
glaciation more than 30 million years ago.

In East Antarctica, basal freeze-on has continued in
the same locations through the last glacial-interglacial transition and
has probably been a persistent process since East Antarctica became
encased in a large ice sheet 32 million years ago. The simple geometry
of the subglacial topography and the stable ice flow in the Dome A
region have enabled us to image this process for the first time.
Although the surface accumulation, surface slope, and bed morphology
vary distinctly on the northern and southern sides of Dome A, throughout
the area almost a quarter of the ice sheet base consists of ice
freeze-on from the bottom. Widespread freeze-on can change the rheology
and modify the flow of the Antarctic and Greenland ice sheets. Inclusion
of these basal processes is essential to produce robust predictions of
future ice sheet change.

The addition of hundreds of meters of ice to the base of
an ice sheet deforms the overlying ice, causing uplifted sections on the
glacier's surface. This changes ice sheet stratigraphy and may affect the
surface accumulation by changing the slope of the surface. The thickest
package of frozen-on ice the researchers found was 1110 m, located at
the downflow end of a 20-km-long valley. The internal layers in the
covering ice are deformed upward over 410 m at the valley head. The
shape of the surface actually reflects the shape of the accreted ice body
and not the underlying bedrock. Radar imaging and its interpretation are
shown in the figure below.

AGAP
radar and lidar data over the freeze-on ice package.

“The accretion sites in the Dome A region are typically
coincident with 5- to 35-m mounds in the ice surface, indicating linkage
between the basal processes and the ice surface morphology,” the report
states. In fact, the freeze-on rates in the Dome A region may be locally
greater than the surface accumulation rates from snowfall. Aside from
changing accumulation rates and ice-flow dynamics, this discovery has
implications for those trying to extend the ice core record farther back
into time.

“the widespread melt required to support the freeze-on
process may have destroyed the ice containing the ancient paleoclimate
records,” Bell et al. state. “Without the inclusion of basal
processes, simple models of ice sheet temperatures cannot accurately
predict the location of the oldest ice.” Knowledge gathered from the
deepest ice cores may need revision.

In an accompanying perspective article, “Antarctica's
Deep Frozen "Lakes",” Slawek Tulaczyk and Saffia Hossainzadeh estimate
the volume of water contained in the accumulated frozen-on ice. “If the
average thickness of Antarctic accreted ice is in the range of 10 m
to 100 m, its volume is around 100,000 to
1,000,000 km3, i.e., much larger than the
estimated volume of Antarctic subglacial lakes,
10,000 km3,” they state, adding “it may
even exceed the volume of all glaciers on Earth outside of the two polar
ice sheets, 180,000 km3.”

Accreted basal ice layers were known from past Antarctic
studies, Tulaczyk and Hossainzadeh note, but the newly discovered ones are
considerably thicker and more widespread. West Antarctica boreholes had
previously encountered accreted ice 5 to 15 m thick. In contrast,
Bell et al. imaged accreted ice that is hundreds of meters thick.
It is now thought that basal conditions favor freezing over approximately
half of the area of the Antarctic ice sheet, as shown in the figure below.
Melting is positive and shown in warm colors; freezing is negative and in
cold colors.

Estimated
Antarctic basal melting and freezing rates in mm/yr.

The implications of the research are clear. Bell and
colleagues summed the situation up this way: “Widespread freeze-on can
change the rheology and modify the flow of the Antarctic and Greenland ice
sheets. Inclusion of these basal processes is essential to produce robust
predictions of future ice sheet change.” Tulaczyk and Hossainzadeh are
even more to the point:

The discovery of thick, widespread accreted ice layers
changes in fundamental ways our understanding of the Antarctic ice
sheet. Further mapping and modeling of these ice bodies is necessary to
aid the ongoing search for the oldest ice on Earth. New models of
subglacial water generation, flow, and freezing will have to be
developed to account for this large internal mass and heat
redistribution within the ice sheet

These scientists are saying that the new findings
fundamentally change our understanding of ice sheets and their inclusion
in new models is essential. Basically, this means all of the model
predictions of how fast ice is melting and moving to the sea, in both
Antarctica and Greenland, need to be revised. It turns out that all those
model based predictions of an icy Armageddon, with glacial ice racing to
the ocean at ever increasing rates, were not based on reality.

This discovery shows the danger of basing estimates of
future conditions on model output, be it ice flow or climate change. As
fodder for research models are fine, but as a foundation to base public
policy on they are horrid. The public, media and politicians need to
understand that models are not fact, they are at best imperfect
representations of a poorly understood reality.

Be safe, enjoy the interglacial and stay skeptical.

By Doug L. Hoffman at 04/24/2011
- 12:39

Antarctic

Climate Change

glacial

Glacier

Greenland

ice sheet

interglacial

precipitation

Doug L.
Hoffman's blog

Add
new comment

Ice
Cores Samples

Makes one skeptical of findings based on ice core samples. The
conventional thinking was that the deeper you drilled the older the ice.
Now we find that ain't necessarily so.

By Anonymous at 06/07/2011 -
10:25

reply

Scientific
Ignorance

All real scientists know we are ignorant of how nature works. The
yelling and kvetching over melting icecaps is a case in point. The closer
we look the dumber we find we are.

By Anonymous at 04/28/2011 -
10:52

reply

that
isnt all its gaining

http://www.sciencedaily.com/releases/2011/04/110419191022.htm

King Crabs Invade Antarctica

ScienceDaily (Apr. 26, 2011) — It's like a scene out of a sci-fi
movie -- thousands, possibly millions, of king crabs are marching through
icy, deep-sea waters and up the Antarctic slope

now that sounds like a tasty change i can get behind! Someone pass me
the melted butter ;>)

one thing though that this finding does do is to call into question ice
core's and their usefulness for their historical data. if it is a wide
spread thing, then some cores oldest histories, may in fact be far younger
then believed, which will pose issues with getting accurate data.

and since we are talking about antarctica, i found this
interesting:

http://www.sciencemag.org/content/early/2011/04/20/science.1202131.full.pdf

Over the past half-century, the ozone hole has caused a poleward
shift of the extratropical westerly jet in the Southern Hemisphere. Here,
we argue that these extratropical circulation changes, resulting from
ozone depletion, have substantially contributed to subtropical
precipitation changes. Specifically, we show that precipitation in the
Southern subtropics in austral summer increases significantly when climate
models are integrated with reduced polar ozone concentrations.
Furthermore, the observed patterns of subtropical precipitation change,
from 1979 to 2000, are very similar to those in our model integrations,
where ozone depletion alone is prescribed. In both climate models and
observations, the subtropical moistening is linked to a poleward shift of
the extratropical westerly jet. Our results highlight the importance of
polar regions on the subtropical hydrological cycle.

interesting how they were able to compare computer models with observed
data and it showed how the ozone layer, or lack there of, over the south
pole had such far reaching effects on climate.

im currently enjoying patrick moore's new book, after having finally
read both of yours, and i couldnt agree more with his sentiments about how
limited our current models truly are, and this is just further proof of
that. While they are very useful tools, they are not the crystal balls
some hold them up to be.

enjoy!

By shawnsilvas at 04/27/2011 -
11:50

reply

Old
cores

Not only would the deep ice be younger than expected, but it would be
refrozen melt water. The mixture of gases used for so many proxy
measurments would no longer be trustworthy.

By Anonymous at 04/27/2011 -
12:57

reply

copyright © 2008-2012, Doug L. Hoffman & Allen
Simmons, all rights reserved.

Resilient Earth Books

Visit The Resilient Earth Store!

We
sell all sorts of Resilient Earth
gear.

Most Popular Posts

All time:

Bleached
Coral Reefs Bounce Back

Himalayan
Glaciers Not Melting

Appalachian
Mountains Rock Ice Age

New
"Jelly Pump" Rewrites Carbon Cycle

The
Grand View: 4 Billion Years Of Climate Change

Heat-resistant
Corals Ignore Climate Change Threats

Polar
Bear Ruling Makes Mockery of Legal System

Kudzu
Causes Global Warming!

Biodiversity
Balderdash

Carbon
Sediments Reconsidered

Town's
Schools first to be Heated by Burning Cattle

Little
Ice Age II, The Sequel?

Wind
Power: Green and Deadly

More
Water Vapor Woes For Climate Modelers

Medieval
Warm Period Rediscovered

Blog Post Tags

AGW Antarctic anthropogenic Arctic Atmosphere carbon cycle carbon dioxide Climate Change clouds CO2 Evolution extinction glacial Glacier Global Warming greenhouse Greenland Holocene Ice Age ice sheet interglacial IPCC methane Oil precipitation proxy Resilient Earth sea-level solar wind

more
tags

Current Solar Activity

Click on the image above for the latest view of the Sun.
See the SOHO site for more
information.

Today's popular content

Bleached
Coral Reefs Bounce Back

Appalachian
Mountains Rock Ice Age

True
Alternative Energy: The Power Of Thorium

Town's
Schools first to be Heated by Burning Cattle

New
Ice Surveys Finds Slower Ice-sheet Melting

Parker's
Folly, Doug L. Hoffman's Science Fiction Adventure, Now Available In
Trade Paperback

Orbital
Climate Cycles Reaffirmed, Classical Statistics Denied

IPCC
Gets It Backwards, Drought Causes Warming

When
Humans Almost Went Extinct

Scientifically
Ignorant, Tabloid "Climatologists" Blame Sandy On Climate
Change

more

Visitors

The ResilientEarth News Feed