Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. Earth Science News .




ICE WORLD
NASA Scientists Part of Arctic Sea Ice Study
by George Hale for Goddard Space Flight Center
Greenbelt MD (SPX) Feb 19, 2013


The Polar-5 aircraft, carrying the EM instrument that was used to validate Cryosat-2 sea ice thickness measurements, flying over the validation site. Credit: NERC/UCL/Rosemary Willatt.

New research using combined records of ice measurements from NASA's Ice, Cloud and Land Elevation Satellite (ICESat), the European Space Agency's CryoSat-2 satellite, airborne surveys and ocean-based sensors shows Arctic sea ice volume declined 36 percent in the autumn and 9 percent in the winter over the last decade. The work builds on previous studies using submarine and NASA satellite data and confirms computer model estimates that showed ice volume decreases over the last decade, and builds a foundation for a multi-decadal record of sea ice volume changes.

In a report published online recently in the journal Geophysical Research Letters, a large international collaboration of scientists outlined their work to calculate Arctic sea ice volume. The satellite measurements were verified using data from NASA's Operation IceBridge, ocean-based sensors and a European airborne science expedition. This was compared with the earlier sea ice volume record from NASA's ICESat, which reached the end of its lifespan in 2009.

The researchers found that from 2003 to 2008, autumn volumes of ice averaged 11,900 cubic kilometers. But from 2010 to 2012, the average volume had dropped to 7,600 cubic kilometers - a decline of 4,300 cubic kilometers. The average ice volume in the winter from 2003 to 2008 was 16,300 cubic kilometers, dropping to 14,800 cubic kilometers between 2010 and 2012 - a difference of 1,500 cubic kilometers.

The study, funded by the United Kingdom's National Environmental Research Council ESA, the German Aerospace Center, Alberta Ingenuity, NASA, the Office of Naval Research and the National Science Foundation and led by Professor Seymour Laxon of University College London, marks the first ice volume estimates from CryoSat 2, which was launched in 2010. "It's an important achievement and milestone for CryoSat-2," said co-author Ron Kwok at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Combining the Ingredients
Although CryoSat-2 data show a decrease in ice volume from 2010 to 2012, two years is not a long enough time span to determine a trend. This is where NASA's data and scientists come in. Data from ICESat and IceBridge are freely available, but combining measurements from different sources can be challenging.

Kwok said researchers spent months working out how to compare the datasets and make sure they were compatible enough to compare trends "We participated as collaborators to help interpret results from the datasets we're familiar with," said scientist Sinead Farrell at NASA's Goddard Space Flight Center in Greenbelt, Md.

CryoSat-2 and ICESat both measure sea ice freeboard, that is, the amount of ice floating above the ocean's surface. Researchers use freeboard to calculate ice thickness. This thickness measurement is then combined with ice area to come up with a figure for volume.

The two satellites used different methods for measuring freeboard however. ICESat used a laser altimeter, which bounces a laser off the snow covering the sea ice, while CryoSat-2 uses a radar instrument that measures surface elevation closer to the ice surface. These instruments have a different view of the surface, but researchers found they gave comparable measurements.

Check and Double Check
Comparing the two datasets and ensuring their quality called for additional data. The two satellites do not cover overlapping time spans, so researchers used measurements from upward-looking sonar (ULS) moorings under the ocean's surface, located north of Alaska.

These instruments, operated by the Woods Hole Oceanographic Institution's Beaufort Gyre Exploration Project, provide a continuous record of ice draft - thickness of ice below the ocean's surface - in parts of the Beaufort Sea from 2003 to the present day.

Thickness measurements from these ULS moorings were comparable to ICESat and CryoSat-2 data throughout both missions' time spans. "ULS ice draft since 2003 served as the common data set for cross comparison of the ICESat and CryoSat-2 measurements," said Kwok.

Researchers took extra care to verify CryoSat-2's data as it is a new satellite with a new instrument. In addition to the ULS data, CryoSat-2 measurements were also verified by two airborne science campaigns: flights by an aircraft operated by the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany; and Operation IceBridge, a NASA mission tasked with monitoring changes in polar ice to bridge the gap in measurements between ICESat and its replacement, ICESat-2, scheduled to launch in 2016.

During the 2011 and 2012 Arctic campaigns, the IceBridge team coordinated closely with ESA's CryoVEx program to verify CryoSat-2 data. "IceBridge was used as a validation tool to understand thickness measurements from CryoSat-2," said scientist Nathan Kurtz at NASA Goddard.

The Road Ahead
After months of work, researchers had assembled a multi-year dataset that they could compare to sea ice volume predictions from the Pan-Arctic Ice-Ocean Modeling and Assimilation System (PIOMAS).

Because of the short time span of previous satellite studies, researchers have used models like PIOMAS to simulate changes in sea ice volume. The study's observations show a larger autumn ice volume decrease than predicted, while changes in the winter are smaller than in the model simulation. "It's important to know because changes in volume indicate changes in heat exchange between the ice, ocean and atmosphere," said Kurtz.

This study and the knowledge that the datasets are compatible also serve to lay groundwork for ICESat-2. CryoSat-2 gathers data over more of the Arctic than ICESat did by reaching 88 degrees north (ICESat reached 86 degrees). ICESat-2 will orbit Earth at the same angle as CryoSat-2 and will therefore survey the same amount of the Arctic.

CryoSat-2 is funded through 2017 but will likely operate until the end of the decade, giving overlapping coverage with ICESat-2. This potential overlap greatly improves the prospects for improved knowledge of Arctic sea ice volume. "The hope is that we'll be able to create a multi-decadal record using ICESat, CryoSat-2 and ICESat-2," said Kwok.

.


Related Links
CESat
Operation IceBridge
CryoSat-2
Beaufort Gyre Exploration Project
Beyond the Ice Age






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





ICE WORLD
Rapid changes in Arctic ecosystem during 2012 ice minimum
Bremerhaven, Germany (SPX) Feb 18, 2013
Huge quantities of algae are growing on the underside of sea ice in the Central Arctic: in 2012 the ice algae Melosira arctica was responsible for almost half the primary production in this area. When the ice melts, as was the case during the ice minimum in 2012, these algae sink rapidly to the bottom of the sea at a depth of several thousands of metres. Deep sea animals such as sea cucumbers an ... read more


ICE WORLD
Four guilty of manslaughter in Italy quake trial

Warning of emergency alert system hacks

No health effects from Fukushima: Japan researcher

Aid trickles into tsunami-hit Solomons despite aftershocks

ICE WORLD
Researchers strain to improve electrical material and it's worth it

Explosive breakthrough in research on molecular recognition

Indra Develops The First High-Resolution Passive Radar System

ORNL scientists solve mercury mystery

ICE WORLD
Quantifying Sediment From 2011 Flood Into Louisianas Wetlands

Japanese scientists hunt for groundwater

Landslides delivered preferred upstream habitats for coho salmon

Middle East river basin has lost Dead Sea-sized quantity of water

ICE WORLD
Ice age extinction shaped Australian plant diversity

European sat data confirms UW numbers that Arctic is on thin ice

NASA Scientists Part of Arctic Sea Ice Study

Rapid changes in Arctic ecosystem during 2012 ice minimum

ICE WORLD
Marsh plants actively engineer their landscape

Advance promises to expand biological control of crop pests

Buffaloes a divisive link to Hong Kong's past

Mexico to slaughter a half million chickens over bird flu

ICE WORLD
Flood research shows human habits die hard

Indonesia floods, landslides kill 17

Mystery gold gifts for tsunami-wracked Japan port

Shimmering water reveals cold volcanic vent in Antarctic waters

ICE WORLD
South Sudan president retires over 100 army generals

Pistorius shooting puts spotlight on S.African gun violence

US warns of tensions on Sudan-S.Sudan border

Jane Goodall: chimp scientist turned activist

ICE WORLD
Tiny mutation had big evolutionary impact

Bilingual babies get good at grammar

UF researchers include humans in most comprehensive tree of life to date

The last Neanderthals of southern Iberia did not coexist with modern humans




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement