Tag Archives: Greenland

Greenland’s Warming, Melting, and Sliding to Sea

Posted on June 27, 2012 by | 12 comments

Greenland is warming, Greenland’s warming is melting its ice, and Greenland melting ice is raising global sea level. All true, but it all has happened before during the last 100 years or so. Our technology to extract small signals buried deep in noise from both our backyard and remote Greenland is unprecedented. This skill should not fool us, that the large changes that we see in Greenland and elsewhere have not happened before. They have, but memory is a fickle thing, as “new” is exciting, while “old” is often forgotten and considered unimportant. Those who live in the past are doomed to miss the present, those who ignore the past, are doomed to repeat it. We need to learn from the past, live in the present, and prepare for the future.

Preparing for an expedition to Nares Strait between northern Greenland and Canada in about 5 weeks, I am exploring temperature data from land, satellites, and ocean sensors to get a feel for what has changed. I started with data from weather stations such as the U.S. Air Force Base Thule , Canada’s former spy station Alert, and Denmark’s Station Nord about 700-1000 miles from the North Pole. So, it is cold up there:

Annual cycle of air temperature (bottom panel) from south to north at Thule (red), Grise Fjord (green), Alert (blue), and Cap Morris Jesup. Data years (top panel) for each year day are degrees of freedom. For each place two temperature curves indicate upper and lower limits of the climatological mean temperature for that day at 95\% confidence.

Well, we knew that, but the real question is: Has anything changed? Has Global Warming reached Greenland? The plot above does not tell, but this one does:

Annual averages and trends of air temperature anomalies for the 1987-2010 period for (top to bottom) Station Nord (Greenland), Alert (Canada), Grise Fjord (Canada), and Thule (Greenland). Scales are identical. The trends are fitted to daily, not annual data. The annual averages are shown for display purposes only.

To some it screams: “Warming, melting, Greenland is surging to sea.” [It is, but it did so before.]

There is lots of fancy signal processing that goes into this (see Tamino or a class I teach) to make a firm statement:

The air around northern Greenland and Ellesmere Island has warmed by about 0.11 +/- 0.025 degrees Celsius per year since 1987. North-west Greenland and north-east Canada are warming more than five times faster than the rest of the world.

This must be huge (yes, it is), it must have an effect on the Greenland ice sheet (yes, it does), and this must raise sea level (yes, perhaps 10 cm or 3 inches in 100 years, Moon et al., 2012).

Now where is the catch?

The catch is that my records all start in 1987, because that is the period for which I have actual measurements from all those stations. My satellite record is even shorter: it starts in 2000, but with lots of work can be extended back to 1978. And my ocean record is shorter yet: it starts in 2003. There just are no other hard data available from north-west Greenland.

So, does this mean we are stuck with the gloom and doom of a short record?

No, but we have to leave the comforts of hard, modern data with which to do solid science. People have to stick out their necks a little by making larger scale interferences. Based on the 1987-2010 results shown above, I can now say that trends and year-to-year variations are all similar in Alert, Thule, Kap Morris Jesup, etc., etc., so I will use the 60 year Thule record to make statements that somewhat represent all of Nares Strait. I could also start looking for softer and older data. With soft data I mean sketchy ship logs kept by whalers, tense expedition reports of starving explorers (Lauge Koch, Knud Rasmussen, Peter Freuchen), and imperial expeditions (George Nares, Adolphus Greely).

Further south there are a few ports where government or trading authorities started records early. The current capital of Greenland, Nuuk (formerly Godthab) is such a place. The Nuuk record starts 1881. And what I find is that the current warming in Greenland has happened just as dramatic as it does now in the 1920ies and 1930ies [well, except for the 2010 spike, but that story is still ongoing]:

Data from Nuuk, southern Greenland, where the temperature record goes back to 1881 (monthly data from NASA/GISS). The dashed line indicates 1987.

The trend is statistically significant, about 0.008 +/- 0.03 degrees centigrade per year or about 10 times smaller than what it is for northern Greenland starting in 1987. So the devil of Greenland warming, melting, and sliding to sea is in the details or records that are too short. The Global Warming signal is in there, but how much, we do not know and perhaps cannot know. Furthermore, most of the globe of “Global Warming” is covered by water and the ocean warming we know little about. Recall, my ocean record off northern Greenland only starts in 2003 and ends in 2009 or 2012, if we recover computers, sensors, and data from the bottom of Nares Strait this summer.

Greenland’s data and physics of ice, ocean, and air are exciting and all show dramatic change. To me, this is a big and fun puzzle, but one has to be careful and humble to avoid making silly statements for political purposes that are not supported by data. Do I think Global Warming is happening? Absolutely, yes. Do I think it is man-made? Probably. What do I do about it? I ride my bicycle to and from work every day. And that’s what I do next … bicycle home.

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Ice Arches and Gothic Cathedrals

Posted on June 11, 2012 by | 6 comments

Soaring towards heaven awash in light, Gothic Cathedrals awed medieval kings, jesters, and peasants alike. Their upward pointing arches allowed walls of stained windows to filter light into these massive buildings when most dwellings from royal castle to decrepit hut were dark, damp, and filthy. While the power of god was both invoked and abused, it was physics and engineering that allowed these cathedrals to scrape the skies. A delicate balance of forces is of the essence to avoid accelerations and collapse.

Arched windows within an arch inside the Cathedral of Reims, France.

Hence it should not surprise that ice arches buttressed by land show similar elegance and stability, but also dramatic collapse. When these ice arches form and collapse is one factor to determine when the Arctic Ocean will be free of ice in summer.

June-10, 2012 ice arch in Nares Strait between northern Greenland and Canada. The arch has been in place since Dec.-8, 2011.

Nares Strait Jun.-10, 2012 image showing land-fast ice between northern Greenland and Canada as well as the ice arch in the south (bottom left) separating sea ice from open water (North Water).

The Nares Strait ice arch forms between December and April most winters. Unlike the medieval cathedrals it consists of blocks of ice. Once in place, the arch shuts down all ice movement. The ocean water under the ice moves undisturbed southward sweeping newly formed ice away. This creates the North-Water polynya, first reported by William Baffin in his ship logs in 1616. The North Water supports wild life for millenia providing food and trading items for people. Even viking remnants from the time the first Gothic Cathedrals were built in Europe were found here: sections of chain mail, iron point blades, cloth, and boat rivets.

I want the ice arch in Nares Strait to collapse as soon as possible so that a Canadian ice breaker can get us to where we like to recover instruments and data that we deployed in 2009. And while I researched the stability of ice arches and studied Moira Dunbar’s 1969 satellite imagery, I came across a wonderful NOVA broadcast on medieval skyscrapers of glass and stone.” PBS stations will show it on Sept.-9, 2012.

Digging a little deeper, I also found a series of Open University podcasts and videos. My favorite 3-minute segment covers lines of thrust where barely connected irregular blocks of wood form a surprisingly stable yet wobbly arching bridge. If you want to build your own arch, then play interactively for fun with the physics of stone arches.

Since I want to understand and predict when the ice arch of Nares Strait collapses, I must understand how medieval architects and engineers designed their Gothic Cathedrals. I will also need understand why some cathedrals are still standing while others collapsed. My icy building blocks in Nares Strait are not as solid as the stones of Reims Cathedral, but unlike the medieval scientists, today we have computers and mathematics to help … as well as more than 800 more years of experience in science and engineering.

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Posted in Ice Arch, Oceanography, Uncertainty

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Last Image of Nares Strait from Europe’s Environmental Satellite

Posted on May 9, 2012 by | Leave a comment

The European Space Agency announced today that one of its primary environmental satellites died. For over a months now engineers could neither receive data nor send commands to the 10-year old veteran of earth science research whose design life was 5 years. The last image received for my study area between northern Greenland and Canada shows Petermann Gletscher and ice-covered Nares Strait:

The rectangle between Franklin Island, Greenland and Ellesmere Island, Canada shows the site where in August 2012 we hopefully will recover data from an array of ice and ocean sensing equipment that we put there in 2009.

It was during this 2009 International Polar Year expedition to Nares Strait that I discovered satellite remote sensing in a new way, that is, accessing the raw digits sent down to earth from the NASA’s Aqua and Terra satellites that contain Moderate Resolution Imaging Spectroradiometer (MODIS) sensors. These two sensors are as old or older than its European companion. MODIS are now the only optical sensors at better than daily resolution which check the land, ocean, and ice now that the European satellite is not talking with us anymore.

For me, the most spectacular use of Europe’s EnviSat was its ability to document how the 2010 Petermann Ice Island wiggled its way out of its constraining fjord into Nares Strait. A movie of daily radar images is attached:

Petermann Ice Island 2010 slow movement through Petermann Fjord, break-up on Joe Island, and swift movement southward in Nares Strait. Click on image to start movie.

Unlike its Canadian counterpart, RadarSat, the imagery from the European radar (ASAR) was distributed widely, free of charge, and became useful to research communities and a wider public. The Danish Meteorological Institute provides an archive of imagery from both US and European satellites for all of coastal Greenland that just lost its European imagery (http://ocean.dmi.dk/arctic/modis.uk.php). Unlike the now defunct EnviSat, RadarSat is a for-profit commercial enterprise unaffordable to scientists or a public. The Canadian government funded development, launch, and initial data processing before giving it away to a private corporation. Ironically, the largest paying customer for its expensive products is the Canadian Government, but the data are rarely used for public education or research. They may as well be secret.

So, the demise of EnviSat is sad news. It removes a semi-public eye in the sky. Lets hope, that its replacement by the European Space Agency receives the urgent attention that it deserves.

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Greenland’s Glaciers, Science, Sea-Level, and Teachers

Posted on May 4, 2012 by | 1 comment

Science Magazine hit climate change hard today. They cover how Greenland’s glaciers and ice sheets change as they interact with the ocean and contribute to sea-level rise feature in 3 related stories. The reality check of these three stories puts a damper on the usual doomsday scenarios of those whose skill is limited to grabbing public attention to move a political agenda. Real science works differently:

May-4, 2012 Science Magazine Cover: A jumble of icebergs forms in front of the heavily crevassed calving front of Jakobshavn Isbræ, one of the fastest outlet glaciers draining the Greenland Ice Sheet. The ~5-kilometer-wide ice front rises ~80 meters out of the water and extends more than 600 meters underwater. Recent research shows that the speeds of Greenland glaciers are increasing. See page 576. [Photo Credit: Ian Joughin, APL/UW]

The solid new research is that of Twila Moon, a graduate student at the University of Washington whose dissertation work relates to the evolution of Greenland’s outlet glaciers over the last 10 years. She uses data from Canadian, German, and Japanese radars flown on satellites. She applies fancy mathematics to the data and feds data and mathematics into modern computer codes. And with all that, she cracks the puzzle on how fast more than 200 of Greenland’s largest glaciers go to town, eh, I mean, to sea. Furthermore, she shows how this flow has changed over the last 10 years.

Twila Moon, graduate student and scientist at the University of Washington and first author of “21st-Century Evolution of Greenland Outlet Glacier velocities” that appeared in Science Magazine on May-4, 2012. [Photo Credit: APL/UW website]

Back in the days of 2008, crude, but simple back-on-the-envelope calculation suggested that Greenland contributes 0.8-2.0 meters to global sea-level rise by 2100. In stark contrast, the 2000-2010 data now reveals, that even the low-end estimate is too high by a factor of 10. A glacier here or there may accelerate at a large rate to give the 0.8-2.0 m, but these rates do not occur at the same time at all glaciers. Ms. Moon’s more comprehensive and careful analyses of accelerating glaciers bring down Greenland’s contributions to sea-level rise to below 0.1 m by 2100, that comes to about 1 mm/year or an inch in 30 years.

A commentary written by Professor Richard Alley relates to the ice-sheets that feed these glaciers. Dr. Alley is famous for his work on Greenland’s ice sheet as he participated in 2-Mile Time Machine, a project that revolutionized the way that we view climate and its variability the last 100,000 years. The title refers to the 2-mile long ice-core from Greenland’s ice-sheet that trapped and stored air and stuff from the last 100,000 years. Dr. Alley is also featured in Andrew Revkin’s dot-earth blog of the New York Times as the Singing Climatologist. His comment on “Modeling Ice-Sheet Flow” references Ms. Moon’s observations as evidence that ice sheets change quickly. It also contains the sentence that “The lack of a firm understanding of ice-sheet-ocean interaction, constrained by reliable ocean data, remains a critical obstacle to understanding future changes.” I could not agree more with this sentiment, these data are darn hard to come by … not as hard as getting to the bottom of the 2-mile time machine, though.

While Ms. Moon addressed changes in Greenland’s glaciers, Dr. Alley addressed the ice-sheets feeding those glaciers, another comment by physical oceanographer Dr. Josh Willis of NASA’s Jet Propulsion Laboratory relates to the sea-level changes caused by accelerating glaciers to make “Regional Sea-Level Projections.” He works mostly on massive computer models which devour massive amounts of data to get climate right. Sometimes this works, sometimes is does not, but he does comment that these earth system models give sea-level projections that are a factor 2 smaller than those derived from statistical relations and semi-empirical models using surface temperature and radiative forcing to extrapolate past trends into the future. The difference probably relates to smaller and more regional processes that involve the physics of ocean circulation and its interaction with ice-shelves off Antarctic and Greenland.

Dr. Josh Willis conducting an oceanographic experiment studying sea temperatures between New Zealand and Hawaii. [Credit: JPL/NASA]

My great oceanography hero, Henry Stommel of Woods Hole oceanographic Institution once wrote in his “View of the Sea,” that “Science is both an individual and a social activity.” I am sure that graduate student Ms. Moon, NASA researcher Dr. Willis, and veteran professor and science communicator Prof. Alley all work hard and lonely at night some nights … and party hard while discussing science and adventures over a beer, dinner, coffee in some city, remote field, or on a ship. The one group of people missing in this picture are … the science teachers, that is, those dedicated, over-worked, and under-paid professionals who encourage, motivate, and helped us to become scientists before we went to college.

The editorial of this week’s Science Magazine is entitled “Empowering Science Teachers.” It compares the social and professional status of pre-college science teachers in Finland and the USA. I will only say in the words of Anne Baffert, chemistry teacher at Salpointe Catholic High School in Tucson, Arizona, that too many science “… teachers work in a command-and-control environment, managed by those who lack any real understanding of how to improve the system.” The editorial suggests on how scientists can improve science teaching, such as “… active involvement in science through structured collaborations with scientists …” Apparently, Finland succeeds while we in the USA are challenged to get our graduate students into a pre-college class room teaching. More stuff for me to munch on here …

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Heat Sensing Eyes “See” Arctic Ice Thickness

Posted on January 26, 2012 by | 1 comment

The Arctic sea ice is disappearing before our eyes as we extended them into space in the form of satellites. Every summer for the last few years the area covered by ice is shrinking during the summer when 24 hours of sunlight give us plenty of crisp images. But what about winter? What about now? And does a picture from space tell us how thick the ice is?

Nares Strait between northern Greenland and Canada on Aug.-13, 2005 with Petermann and Humboldt Glaciers at top and center right from MODIS imagery using red, blue, and green channels.

It is dark in the winter near the north pole as the sun is below the horizon 24 hours each day, but there are many ways to “see” in the dark as flying bats aptly show. They send out sound that bounce off objects from which bats reconstruct objects around them. We use radar from space to do to the same with radio waves to “see” different types of ice at night from satellites. We can also use tiny amounts of heat stored in water, ice, snow, and land to “see” at night. Someone breathing down your neck at a cold dark corner will make our heart beat faster as we “see” the heat not with our eyes, but with our skin. I digress, as I really want to talk about icy Arctic seas and how we can perhaps “see” how thick it is with our eyes in the sky.

The most accurate and pain-staking way to measure ice thickness is drill holes through it. This is back-breaking, manual labor away from the comforts of a ship or a camp. One person watches with a shot-gun for polar bear searching for food, not our food, we are the food. The scientist who does this sweaty, dangerous work on our Nares Strait expeditions is Dr. Michelle Johnston of Canada’s National Research Council. She is a petite, attractive, and smart woman who is calm, competent, and comfortable when she leads men like her bear-like helper Richard Lanthier into the drilling battles with the ice. She gets dirty, cold, and wet when on her hands and knees setting up, drilling, cutting, measuring:

Dr. Michelle Johnston assembling ice drilling gear in Nares Strait with Greenland on the horizon. The Canadian Coast Guard Ship Henry Larsen in the background with its helicopter hovering.

She measures temperatures within the ice and tries to crush it to find out how strong it is. All of this information guides ship operators on what dangers they face operating in icy seas. Drilling over 250 such holes across a small floe on the other (eastern) side of Greenland, Dr. Hajo Eicken showed how one large ice floe changes from less 1 meter to more than 5 meters in thickness. He also discovered that the percentage of thick and thin ice of his single 1 mile wide ice chunk is similar to the percentages measured by a submarine along a track longer than 1000 miles.

This was a surprising result in 1989 and we use it to estimate ice thickness more leisurely sipping coffee in our office. From the same satellite that gives us crisp true color images in summer as shown above, we get false color images of temperature as shown below.

Map of Nares Strait, north-west Greenland on March-25, 2009 showing heat emitted during the polar night from the ocean through the ice, and sensed by MODIS satellite.

A graduate student of mine, Claire Macdonald, is trying to convert these temperature readings into ice thickness for Nares Strait. She showed me the first promising results today. The plot below shows the distribution of “thermal” ice thickness for a small square in Nares Strait Dec.-1, 2008 through Mar.-1, 2009 when no clouds were in the area. Note the two distinct and separate clusters with thicknesses below 1 meter and above 2 meters. They represent thin ice formed in 2009 after an upstream ice arch blocked all flow of thicker ice from the Arctic Ocean to Nares Strait. The thicker ice passed the study area at times when the thick, hard multi-year Arctic ice entered Nares Strait freely from the Arctic Ocean.

Distribution of "thermal" ice thickness from satellite for Nares Strait Dec.-1, 2008 through Mar.-1, 2009. (Credit: Claire Macdonald, Jan.-26, 2012)

Much work remains to be done: Claire is comparing the “thermal” ice thickness with “acoustic” ice thickness measured by sonars moored in the water below the ice. It then will be exciting to explore “thermal” thicknesses for all of Nares Strait. Winds and ocean currents will pile ice up in some areas making it thicker while they spread ice out making it thinner. Claire and I have worked with such wind and ocean data. Science is never finished as each question answered raises a host of new ones.

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