Cryosphere Part 2: Greenland

Global Environmental Change – Lecture 6 Spring 2015

Greenland Map• Greenland is the third largest

country in North America with an area of 2,166,086 km2 (slightly more than 3x Texas)

• Ice-free 0.45 million km2

• Ice-covered 1.71 million km2

• Ice volume 2.85 x 106 km3

(2014 data)

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Ice Graphic

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Greenland’s Climatic Roles• The ice on Greenland plays several important roles

Keeps sea level 7 meters lower than it otherwise would be Has a regulatory role on:

• Ocean circulation – specifically the Meridional Overturning Circulation

• Regional atmospheric circulation

• Global heat transfer

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Glacial Melting• The ice sheet is losing volume from its edges at much faster rate

than predicted, and the sides of the ice sheet are losing mass much more quickly than it can accumulate in the interior

• Loss is partially due to the increase in runoff from melting caused by warm-weather events, a process called “dynamic thinning”

• Dynamic thinning does not affect all glaciers equally Glaciers lying on top of bedrock that smoothly slopes toward the sea are most

strongly affected Efforts are currently underway to map subglacial topography

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Initial Dynamic Thinning• When it gets warm enough, the surface snow and ice begin to

thaw

• Melt water either pools or flows in rivers along the surface, or begins flowing under the snow that covers the ice of the sheet

• In the process, it flows into small cracks, enlarging them as it moves towards the bottom of the ice sheet

• The amount of melt water traveling through these fissures varies greatly

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Accelerating Dynamic Thinning• As surface melt increases, it collects into rivers that carry it to

turquoise blue pools or plunge into crevasses or ice tunnels called “moulins”

• Moulins can extend downwards hundreds of meters, reaching the base of the glacier, or can flow within the glacier

• Wherever the water ends up, moulins can affect both the melting rate and also the velocity of a glacier

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Effect of Melting• Meltwater ponds on the surface decrease albedo, absorbing more

solar radiation, and causing further melting

• Streams bring surface heat, in the form of water, down through the glacier to the bottom of the ice sheet

• Water on the bottom of the glacier acts as lubrication for the glacier, which then gains speed as it flows downhill towards the sea

• Small amounts of melting can have a large effect

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Meltwater Lake

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Meltwater Lake a Few Days Later

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The Moulin that Drained the Lake

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Ice Canyons

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Ice Loss Rate• NASA study showed an increase in

melting of 35% in 2003 relative to the 1993-1999 base period, during which ice losses and gains were nearly balanced

• Scientists at NASA's Goddard Space Flight Center, Greenbelt, Md., report that Greenland's low coastal regions lost 155 gigatons of ice per year between 2003 and 2005 from excess melting and icebergs, while the high-elevation interior gained 54 gigatons annually from excess snowfall

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• NASA satellite data has revealed regional changes in the weight of the Greenland ice sheet between 2003 and 2005.

• Low coastal regions (blue) lost three times as much ice per year from excess melting and icebergs than the high-elevation interior (orange/red) gained from excess snowfall.

• High resolution image Credit: Scott Luthcke, NASA Goddard

Ice Loss• Monthly mass anomalies (in Gt)

for the Greenland ice sheet since April 2002 estimated from GRACE measurements

• The anomalies are expressed as departures from the 2002-2014 mean value for each month

• For reference, orange asterisks denote June values (or May for those years when June is missing).

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How Climatologists Have Fun …

Climate Records• Climate data beyond human records can be

obtained from a number of sources: Ice cores, principally from Greenland and

Antarctica, but also from mountain glaciers Calcium carbonate from oceanic sediments Pollen records Tree-rings

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Ice Cores• Ice cores can be obtained by drilling from the surface through

10’s, 100’s, or 1000’s of feet of ice

• Isotopic data from 18O/ 16O and 2H/1H records provide a proxy for temperature at the time the ice formed.

• Bubbles of gas trapped in the ice allow allow determinations of carbon dioxide in the atmosphere in the past

• The amount of dust in the cores gives an indication of rainfall amounts and wind speeds

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Ice Cores in Greenland• The first ice core drilling in Greenland was carried out in 1955

by the U. S. Army Snow, Ice and Permafrost Research Establishment (SIPRE)

• The drilling took place at Site 2 and was part of the preparations for the International Geophysical Year in 1957

• Using the Site 2 ice core, Chester C. Langway from SIPRE initiated the modern era of multidisciplinary ice core studies including detailed isotope profiles

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Early Drilling• From 1963-1966 Lyle Hansen

and his co-workers from the U.S. Army Cold Region Research and Engineering Laboratories retrieved a ~1390 m long ice core at the Camp Century site, the first ice core was drilled through the Greenland ice cap

• Stable isotope measurements revealed a climate curve reaching far into the glacial past

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• The ice core drill that penetrated the ice to bedrock at Camp Century in 1966 (Photo: USArmy CRELL).

Early Drilling• A new drill was developed and used to retrieve a

more than 2 km long ice core from the DYE-3 drill site in Southern Greenland

• In 1992-93, two parallel deep drilling projects were completed

• They were located about 30 km apart near the Summit of the ice cap

• The mainly European GRIP project and the American GISP2 project each retrieved 3 km long ice cores

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Problems with Core Data• The ice cores provided outstanding data of past climate about

105,000 years back in time, but comparisons of the two ice cores made it clear that the stratigraphies of the bottom 300 m of both cores were disturbed

• Therefore, neither record provides the possibility to study the climate of the previous interglacial period, the Eemian (130 - 114 ka) (Eemian is pronounced 'aim-ee-un‘)

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Eemian Ice• During the Eemian, temperatures were between 5 and 9 F

warmer than today, and global sea level was 13 to 20 feet higher

• Under many climate change scenarios, global temperatures are projected to warm a similar amount this century, so understanding the climate of the Eemian could teach us more about the potential effects of warming today

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Eemian Warming• Eemian warming was triggered by increases in summer

sunshine, resulting from variations in Earth’s orbit and axis of rotation

• However, it may be a good model of the man-made climate change expected over the coming centuries. “We are in a similar climate regime as the world was in the early

Eemian,” says Eric Steig, who studies ice cores at the University of Washington in Seattle

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NGRIP Project• The lack of undisturbed Eemian ice in the Summit ice

cores motivated a search for ice core drill sites which will enable retrieval of undisturbed ice from the Eemian period

• The NGRIP project partially accomplished this

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NEEM Project• The NEEM project, a 14-nation research

team, spent four years drilling and analyzing the core

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Moving from NGRIP to NEEM• The project started

in 2007, when 2 tracked vehicles dragged equipment from the previous drill site, NGRIP, to the NEEM drill site. 

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Shower Facilities• Photo caption “Shower

deluxe! Outside it´s -23C to -7C, inside is a bucket with 40C hot water. Don´t tread too far in bare feet...”

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NEEM Description• The North Greenland Eemian Ice Drilling - NEEM - is an international ice

core research project aimed at retrieving an ice core from North-West Greenland (camp position 77.45°N 51.06°W) reaching back through the previous interglacial, the Eemian.

• The project logistics is managed by the Centre for Ice and Climate, Denmark, and the air support is carried out by US ski equipped Hercules managed through the US Office of Polar Programs, National Science Foundation.

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NEEM Drill Site• New radio echo sounding profiles were used to identify a drill site with

undisturbed deep layers, but without significant basal melting

• The main objective of the NEEM project (started in 2007) is to obtain a complete Eemian record – NEEM stands for North EEMian)

• In 2008, the NEEM camp was established and the pilot hole was drilled

• From 2008-2012, a 2,540-m-long ice core was drilled through the ice at the NEEM site, Greenland (surface elevation 2,450 m, mean annual temperature -29 C, accumulation 0.22 m ice equivalent per year)

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Drilling an Ice Core• Diagram shows the pieces of the

drill used to drill the NEEM site

• The drill is about 13.5 meters long, and is shown here with the outer barrel (indicated by green) removed

• When operational, only the drill head and the anti-torque section (lower right) are visible

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Ice Core• Photo shows an ice

core from 2010

• The length of each core is carefully logged

• Photo: Kenji Kawamura

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Ice Close-Up• Close to the

bottom bands of small stones and dirt are visible

• Photo: Kenji Kawamura

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Ice Core Video

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Air Transport Video

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• Getting to and from the NEEM site• C-130 Hercules on skis

NEEM Publication• The results were published in Nature on

January 23, 2013

• The core was not without problems: the core’s lowest layers had been deformed and folded by the constant movement of the ice sheet, similar to earlier cores

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Analyzing the Ice• Main objective: Understanding the dynamics of the climate system, which

involves many different types of measurements:  Isotope ratios of the ice reveal past temperatures in Greenland and at the source areas that

supply the moisture that ends up as precipitation over the ice sheet Impurities in the ice reflect the impurity load of the atmosphere of the past Gas bubbles trapped between the snow crystals contain samples of the atmosphere of the

past, reflecting the atmospheric composition, e.g. the amount of greenhouse gasses Other properties including the crystal structure of ice, the temperature of the bore hole, and

the content of biological material in it also provide information about past climatic conditions

• The analysis of the more than 2½ km ice core were performed at the Centre for Ice and Climate and cooperating research groups from 13 nations.

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Complete Record• Unlike some previous cores, this one was complete, if distorted

• Dr. Dorthe Dahl-Jensen, a paleoclimatologist at the University of Copenhagen who led the NEEM project said:

• “Of course we had hoped for a purer record, but it is a fantastic record even so, and it does have all the information we needed to reliably reconstruct the Eemian climate and ice-sheet history.”

• The project took four years to complete because the disturbed layers had to be painstakingly examined using a variety of techniques to unravel the distortion

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NEEM Results• The present day annual

temperature at the NEEM site averages about -25C

• 6,000 years after the onset of the Eemian, temperatures were about 8C warmer than they are at present

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NEEM Results• The ice sheet at the NEEM site is

about 2.5 kilometers thick

• Before the Eemian, the ice sheet was about 200 meters thicker than it is today, based on the air content of the ice, which changes as ice gets thicker

• 6,000 years after the onset of the Eemian, the ice level was about 130 meters lower than it is at present, indicating a total loss of just over 10% at the NEEM site

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Implication of NEEM Results• If the NEEM results are correct, Greenland lost a maximum of

one-quarter of its ice volume

• This implies that Greenland contributed no more than two meters of the Eemian sea-level rise

• Studies of ancient corals and other sea-level markers have led researchers to believe sea-level rise during the Eemian was 6-8 meters, and it was thought Greenland contributed at least half of this

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Dorthe Dahl-Jensen Podcast• In conjunction with the NEEM results published in Nature,

there was a Podcast interview with Dorthe Dahl-Jensen

• (Wait for about 19 seconds for audio to start)

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Note on Diagram• This is the original diagram from

the source

• It was split in a photo editor, and material extraneous to each half was removed

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Comparison of Figures

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July, 2012 Ice Melt Extent• Son Nghiem of NASA's Jet Propulsion Laboratory in Pasadena, CA, analyzed

radar data from the Indian Space Research Organization's Oceansat-2 satellite and noticed that 97% of Greenland appeared to have undergone surface melting on July 12--an event completely unprecedented in 30 years of satellite measurements

• Nghiem said, "This was so extraordinary that at first I questioned the result: was this real or was it due to a data error?"

• Multiple satellite data sets confirmed the remarkable event, though. Melt maps derived from three different satellites showed that on July 8, about 40 percent of the ice sheet's surface had melted, as a strong ridge of high pressure set up over Greenland. By July 12, the melting had expanded to cover 97% of Greenland.

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Rapid Snow Melt

Increase

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Extent of surface melt over Greenland’s ice sheet on July 8 (left) and July 12 (right).

Watson River Bridge

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Albedo Change• Greatest changes in

reflectivity (or albedo, multiply by 100 to get % units) are found where a relatively dark surface of impurity rich "glacier ice" emerges once the snow cover melts

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Summer Albedo Decline• Average surface albedo

of the ice sheet each summer between 2000 and 2014

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Albedo Affect at High Elevation

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Petermann Glacier Calving• A 100 square-mile ice island

broke off the Petermann Glacier. It was the largest iceberg in the Arctic since 1962. Image taken by NASA's Aqua satellite on August 21, 2010

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Petermann 2010 Animation• 7-frame satellite animation shows the

calving and break-up of the Petermann Glacier ice island

• The animation begins on August 5, 2010, and ends on September 21, with images spaced about 8 days apart

• The images were taken by NASA's Aqua and Terra satellites

• Creator: Dr. Jeff Masters

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Deja Vu• A massive ice island two

times the size of Manhattan and half as thick as the Empire State Building calved off of Greenland's Petermann Glacier on Monday, July 16, 2012

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Glacial Acceleration• In the video shown earlier it was stated that

Northern Greenland glaciers had now speeded up – yet (from 2005)

• Have they accelerated now?

• Rignot and Mouginot, (2012) helped to answer the question using data from 2008-2009

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Ice flow in Greenland for the International Polar Year 2008–

2009

Geophysical Research LettersVolume 39, Issue 11, L11501, 2 JUN 2012 DOI: 10.1029/2012GL051634http://onlinelibrary.wiley.com/doi/10.1029/2012GL051634/full#grl29178-fig-0002

• Figure shows that fastest glaciers are still in the south, but Petermann in the north is now moving quickly, as are some to the NE