Pine Island Glacier Ice Island 2012 Shoving Off

Posted on February 1, 2012 | 3 Comments

NASA published a stunningly crisp image of Pine Island Glacier (PIG), Antarctica yesterday that is already out of date, because the PIG is on the move. Glaciers change rapidly these days and the speed of the PIG is anything but glacial. The image below from Nov.-13, 2011 shows a massive crack that will develop into an ice island about 3-4 times larger than the one formed from Petermann Glacier, Greenland in 2010. While the image indicates that the part seaward of the crack is still attached, I am convinced that it is already moving independently of the glacier.

Nov.-13, 2011 image of Pine Island Glacier, Antarctica from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument. Area shown cover 27 by 32 miles or 44 by 52 kilometers. Image Credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.

The same Terra space craft that provides the very crisp and high-resolution ASTER image also has sensors that image a larger area at slightly coarser 250 meter resolution. And monday was again an exceptionally clear day over Pine Island Glacier that revealed this (false color) image of radiation received at a “color” that is out of range of our eyes, the near infrared (865 nanometers):

Pine Island Glacier, Antarctica as seen Jan.-30, 2012 from MODIS sensors on Terra spacecraft. The crack is visible as the white line. For reference I am also showing where the front of the glacier was seven years ago with a thin black line. The thick black line shows where the glacier is grounded to the bedrock more than 1000 meters deep (grounding line).

The glacier has advanced a fair amount, the crack breaking off is a perfectly normal event. This is what tidewater glaciers do, they move out to sea and break off icebergs and ice islands. Subtracting the January-30, 2012 image from a Nov.-3, 2011, I think that the thick red line below shows how far and fast the new ice island has moved the last 3 months. Its speed is at least ten times that of the glacier behind the crack:

Difference of two MODIS images, thick red line on left (seaward edge of glacier) shows the area that the new ice island had moved into on Jan.-30, 2012 that was water on Nov.-3, 2011.

Lets leave the boring crack alone, nothing to worry there. What is important at Pine Island Glacier is the retreat of the grounding line, the location where ice, ocean, and bedrock meet. All ice located seaward of the grounding line is floating and does not add to rising global sea level. [Actually, it does raise sea level a tiny amount on account of subtle nonlinearity on how volume of water and ice are influenced by temperature, salinity, and pressure, but lets neglect this detail for now as everyone else does for a good reason).

It is the ice landward of the grounding line that will raise sea level as it passes the grounding line and becomes floating ice. And the thickness of this part of the glacier is decreasing at a rapid and alarming rate, because the glacier is melting from below by the ocean and much of the bedrock landward is below sea level, thus allowing the PIG to become “unhinged.”

The problem with this process is that we cannot see it as easy from space, as we can see changes at the surface. The ocean melting does not give the stunning images that portray drama, concern, and excitement the same way that new ice islands do. Yet, for most large glaciers like Pine Island, Antarctic and Petermann, Greenland, the oceans are eroding and melting these glaciers from below. It is the physics on how this works that we scientists do not yet know and understand very well. It is one thing to have a theory and perhaps a model, but only hard data from the ice and the ocean will give us the confidence and understanding to make smart decisions that balance our energy use contributing to global warming with the need to economically develop. Smart development allows us to live better lives and cope with calamities, some of which may be caused by global warming and the sea level rise it brings.

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Heat Sensing Eyes “See” Arctic Ice Thickness

Posted on January 26, 2012 | Leave a 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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Physics and Engineering of Breaking Dams, Glaciers, and Tides

Posted on January 19, 2012 | Leave a comment

The title “Bombing Hitler’s Dams” fascinated me when I saw it featured on my TiVo last night. The story told was that of a group led by a smart, creative, and somewhat crazy Cambridge University engineer Dr. Hugh Hunt trying to recreate all the engineering elements needed to blow up a dam with a bomb that skips along the surface of the water the same way that a flat stone skips over a calm pond. While we all know intuitively how to throw a flat stone at the right speed at the correct angle, imagine to do it from an aircraft dropping a bomb to skip a few hundred yards over the surface of a reservoir, kiss the dam, sink, then blow it up via a depth charge. After many elaborate tests starting with 3 foot baby’s pool 5 inches deep, the show concluded with the real blowing up of real dam in northern Canada by a much enlarged group of engineers, construction workers, students, pilots, contractors, etc.

Photograph of the breached Möhne Dam taken by Flying Officer Jerry Fray of No. 542 Squadron from his Spitfire PR IX, six Barrage balloons are above the dam

If you think this is hard to do, it is. On May 16/17, 1943 a British bombing raid called “Operation Chastise” deployed cylindrical drums filled with explosives like skipping stones to hop over torpedo nets meant to protect the dams from subsurface mines. Two of three targeted dams were blown up, 53 airmen perished, German heavy industry in the Rhine-Ruhr valley was disrupted for 4 months, and over 1500 civilians drowned in the flood wave created by the breaking dams:

The story reminds my of my adviser, Dr. Richard Garvine (an aeronautical engineer by training) whom I met in 1986 while a physics student from Germany studying physical oceanography for a year in Bangor, Wales. Rather than returning to Germany, I went to the United States for graduate school where I met my sweetheart. One of my first graduate assignment was to study the “breaking dam” problem (Stoker, 1948: “The Formation of Breakers and Bores”, Communications of Pure and Applied Mathematics, 1, 1-87). The “breaking dam” problem is now a classical problem in fluid dynamics that relates to breaking waves, tsunamis, tides, as well as the discharge of fresh water from cooling plants, estuaries, and glaciers. I applied it to tides in the Conway Estuary in North-Wales for my MS thesis that the Swedish Royal Society saw fit to publish as my first contribution to science.

Conwy Estuary at its mouth near high tide.

I stole the above photo of the Conway Estuary, North Wales from a set of beautiful travelogues of an area where I camped for 6 weeks to guard instruments that measured currents along the 50 km tidal reach of this beautiful estuary. The tides rush in like the waves of a breaking dam, yet, they do not break (no bore forms, why?). To model the physics, I needed to study the work done by American, British, and French engineers who labored hard to defeat Nazi Germany by blowing up actual dams developing new and applying old ideas in physics and engineering along the way. Studying their work, I got my answer, too.

Addendum: A review of the aftermath and devastation of the 1943 flood wave from a German perspective is posted here with original photos from both British and German sources.

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Pine Island Glacier Grounding and Unhinging

Posted on January 17, 2012 | Leave a comment

I can’t get Pine Island Glacier, Antarctica out of my mind. Checking my e-mail over breakfast, I was alerted to the forum post of Dr. King, a geophysicist working at the University of Newcastle in northern England. His post provided a hint and link to data on where all glaciers around Antarctica are grounded. The file at the National Snow and Ice Data Center was too slow to download at home, so I quickly bicycled to work, got the data, wrote a little script , and plotted Pine Island Glacier’s grounding and “coastline”:

Pine Island Glacier, Antarctica as seen Jan.-12, 2012 from MODIS Terra. The blue colors top-left are ocean, red-yellow are ice. Thick black line shows where the glacier is grounded to the bedrock below sea level, that is, all "red" areas to the left (west) of this line are floating on the ocean. The thin black line is the "coastline." Grounding and coastlines are from National Snow and Ice Data Center'. North is to the top.

The image indicates a problem in a rapidly changing world: Both the “coastline” and the “grounding line” change with time, rapidly so. The black lines shown above come from hundreds of cloud-free satellite images from the 2004/05 summer in Antarctica. Dr. Scambos, Lead Scientist for the National Snow and Ice Data Center painstakingly analyzed these data and assembled them into the “Mosaic of Antarctica.” The derived coastline for the Pine Island region suggests, that the glacier advanced over 10 km in 7 years. The crack behind it identifies the next ice island that, I speculate, has already separates from the glacier, as its front is moving 10 times faster than the glacier itself. The grounding line looks different from one that I have seen before, too, e.g.,

Bottom topography under Pine Island Glacier and grounding line. North is to the bottom. (NASA)

Trying to resolve this issue, I google searched “Pine Island Grounding Line” only to find a number of excellent science essays and publications on the impacts that Pine Island Glacier and its streaming ice have on climate change and global sea level rise:

Good science essays hide in strange places: “West-Antarctic Ice: Slip-sliding Away” by Dr. Bruce E. Johansen of the University of Nebraska makes reference to a 2010 publication in the Proceedings of the Royal Society of Dr. Katz, University of Oxford. This theoretical fluid dynamicist modeled “Stability of ice-sheet grounding lines” . It is a very theoretical paper whose results are summarized in The New Scientist. This is where I am now, hoping on my bicycle to visit my BrewHaHa coffee shop to read the paper away from my desk over lunch.

Oh, I also stumbled into a NASA animation of how Pine Island and adjacent ice streams accelerate and become thinner very far inland as a result. The graphics are stunning, the data are free, and the message is scary, yet, the science is exciting and I feel very lucky to be able to study this. Watch it, get hooked on science, and have fun.

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Pine Island Glacier on the Move

Posted on January 12, 2012 | 1 Comment

Pine Island Glacier, Antarctica, is the focus of a large observational effort to better understand how glaciers and floating ice shelves interact with the ocean.

Pine Island Glacier (view is to the north, ocean in the top left) with crevasses and large crack extending from the east (right) to the west (left) as seen from aboard NASA's DC-8 research aircraft in October 2011. Credit: Michael Studinger/NASA

Scientists, pilots, technicians, and students working with NASA’s IceBridge and NSF’s Antarctic programmes tried hard for several years now to reach this glacier, set up a base, and drill through the 400-600 m thick ice shelf to reach the ocean. The data from these gargantuan efforts will reveal physics of ice-ocean interactions. This process is poorly represented in the climate models that are used to project past and present climates into the future. Harsh and hostile conditions cut these efforts short today, again, as reported by OurAmazingPlanet.

The expedition leader, NASA’s Dr. Bindschadler wrote today, that

A decision had been made by NSF the day we left McMurdo that if the helos were not able to be flown to PIG by Saturday, January 7, this year’s field work would be cancelled … We worked through our cargo—some had not been seen for two years when we tested our equipment at Windless Bight—preparing for either helos or the Twin Otter to start moving us onto the ice shelf. Neither came. Weather worsened.

Despite this dramatic turn of events, skies were clear over Pine Island Glacier today as they on New Year Jan.1, 2012. Two MODIS images show detailed features at 250-m resolution. I here show the near infra-”red” signals that the satellite receives (865 nm). The dark ocean reflects little of red (low reflectance) as it is all absorbed while the bright snow and ice reflects lots of red (high reflectance). Recall that the color “white” looks white, because it reflects all colors into our eyes including red, while “black” absorbs all colors, so none are left to reach our eyes.

Pine Island Glacier and Bay, Antarctica on Jan.-1, 2012 as seen by MODIS Terra, notice the whitish crack near the center of the image.

I show lots of the near infra-”red” as, well, red, and I color little red as blue. I chose the colors of the “crayons” to do the coloring. The technical term for this is contouring. Formally, I am depicting a function f=f(x,y) where f is the amount of red and x and y are locations east and north, respectively.

Pine Island Glacier and Bay, Antarctica on Jan.-12, 2012 as seen by MODIS Terra, notice the whitish crack near the center of the image.

They almost look the same, don’t they? If they were identical, then the difference would get zero. Except, glaciers move, especially this one. It is also about to spawn a large ice island. A crack was first reported in Oct.-2011 by scientists aboard a DC-8 of a NASA Icebridge flight. This crack is also widening as, I speculate, the front moves faster seaward of the crack than it does landward. My question is if I can see movements in these easily accessible public MODIS images. And my first answer, to be refined later, is 80 meters per day plus or minus 50%:

Difference of reflectance by subtracting Jan.-1 reflectances from those on Jan.-12, 2012. Very dark red colors show large positive numbers, meaning that the ice occupies a place on Jan.-12 that was water on Jan.1.

I am neither a glaciologist nor a remote sensing person, so I may be running a few red lights differencing two images and assign meaning to it. For example, I estimate the speed at which the front of the glacier moves by dividing the width of the very dark thick red line (about 1 km wide) by 12 days to get 80 meters per day or 3.5 meters per hour. The error here is at least 2 pixels (500-m), about half the estimated speed. My assumption here is that the high reflectance on Jan.-12 at a location with a low reflectance on Jan.1 means that the “bright” glacier has moved to a place that was “dark” ocean before. There is more to this, but I have to start somewhere.

Incidentally, Dr. Bindschadler, the leader of the current Pine Island field project who had to leave the base camp near Pine Island Glacier today, is the very person who wrote a wonderful peer-reviewed paper in 2010 with the title “Ice Sheet Change Detection by Satellite Image Differencing.” I will need to study it more closely … along with the vagarities of field work in polar regions.

It is difficult to get data from the field as opposed to data from remote sensing or modeling. This is especially true for remote and hostile locations the ice and the oceans interact. It is frustrating to be sent home early because of inclement weather and the very narrow window of opportunity when the few available helicopters and planes can fly or the ships can sail near Antarctica and Greenland.

EDIT Jan.-13: The National Snow and Ice Center estimated speeds of Pine Island Glacier as determined from two LandSat images from 1986 and 1988:

Contours of glacier speeds in meter per year of Pine Island Glacier from 1986 and 1988 LandSat Imagery, National Snow and Ice Center

These speeds are very different, 2-3 km per year versus 1 km in 12 days. The former estimate is made from 2 carefully geolocated images 2 years apart without a crack across the floating glacier, while my estimate yesterday is more noisy, but it is for a segment of the glacier that is barely connected to it. Perhaps we should consider the segment seaward fo the crack a separate ice island that is moving with the ocean rather than the glacier?

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Melting Greenland’s Icebergs and Ice Islands by the Ocean

Posted on January 11, 2012 | 1 Comment

The BBC keeps asking good and penetrating questions about the fate of Greenland’s many icebergs in general and Petermann Glacier’s Ice Island in particular. A poor telephone connection across the Atlantic this morning prevented an interview, but made me answer a number of questions in writing. When answering these questions, I was thinking of those icebergs and ice islands one finds in abundance in the frigid waters of Baffin Bay, the Labrador Sea, and next to Greenland. I am not talking about what happens once icebergs enter the subtropical Atlantic Ocean and meet the Gulf Stream to the south of the Grand Banks, that is a different story.

USCG Healy besides massive iceberg in northern Baffin Bay, July 2003

1. What can icebergs tell us about oceans?

Icebergs are particles that track averaged ocean currents over the top 200-m or so. These currents are often refered to as “geostrophic” currents which is really a different word for an ocean force balance between pressure gradients (estimated from measurements of temperature and salinity changes with depth at many locations) and the Coriolis force due to the earth’s rotation. This is why RADM Edward H. “Iceberg” Smith of the US Coast Guard spent so much time sailing and taking measurements off northern Canada in the 1920ies and 1930ies as part of the International Ice Patrol. His outstanding publications 80 years old are a first example on how to apply theory (the Scandinavian or Bergen School of the 1920ies regarding dynamical physical oceanography) to a very specific application.

2. How does the trajectory of the ice-islands/ and other icebergs show information about the ocean currents?

Ice islands and icebergs are thick (50-200 m) and mostly submerged below the surface. Hence they are largely moved by the ocean currents about 30-200 m below the surface. I think of them as ocean drifters with a very large and deep drogue element that changes with time as the iceberg melts or tips over. This is different from sea ice that may reach only 5-m into the water column and thus only “sees” the very surface layer of the ocean that is largely influenced by winds. This is not entirely true for icebergs, because they are driven by ocean currents below the thin (10-20 m) ocean “mixed layer” that sea ice is embedded in.

3. What are the current unknowns or poorly understood parameters with regards to iceberg science and iceberg interactions with oceans in the High Arctic?

I think the problem with any prediction scheme of individual particles is that the ocean always has a strong turbulent and unpredictable part to it. This problem is fundamentally no different from trying to predict where oil from a spill will come ashore. We can do it “on average” rather well, but we are very poor trying to do in one specific case for a specific iceberg (or spill). Oh, this certainly also applies to climate predictions, easy to do “on average,” very hard to do in a specific case for a specific time and place that may be affected.

4. What sort of temperatures would the water be?

Meltwater plumes at zero salinity with pieces of ice floating in it have a temperature of 0 C, meltwater plumes with pieces of ice in it at ocean salinities have temperatures of about -1.8C, depending on the amount of sunlight and how much mixing takes place, these fresh and very thin surface layers (1-10 meters) can heat up substantially fast, and cool just as fast. In June/July you have 24 hours of sunlight, so temperatures of 4-10 C are not out of the ordinary, but these waters will do very little melting, because most of the mass is well below a 10 m depth of such fresh surface plumes.

Temperature (left) and salinity (right) distribution off Labrador in the summer of 2009 with depth and distance from the coast (from Colbourne et al., 2010). Note the very cold waters near the freezing point (blue and purple) on the continental shelf below 50-m depth.

5. How would changes in ocean stratification and temperature alter the melting of icebergs?

First, ocean temperature (or heat) and stratification are two very different things. In the Arctic almost all stratification is done by salinity, temperature is a tracer that has very little effect on density stratification. This is also the reason, that most of the ocean’s heat in the Arctic is at depths 200-400 m below the surface. This warm water does NOT rise towards the surface, because it is also salty water, it is often refered to the Atlantic Layer. This deep reservoir of heat is what many oceanographers (myself included) have in mind when they talk about the melting of Greenland’s glaciers by the ocean from below.

Petermann Glacier, for example, has a grounding line at 600-m below the surface. This grounding line is in contact with the heat from the Atlantic Layer that is melting it, but the melted water is fresh and cold, immediately stratifying the water column under the ice, so a source of energy is needed also to move or mix this cold fresh melt water away. An inclined slope may do so, tides may do so, internal waves traveling and breaking on the interface between cold-fresh and warm-salty waters may do so. At Petermann Glacier this Atlantic layer does not reach most of the floating element of this glacier, because it is only 100-200 m thick and thus does not extend into the heat of the Atlantic Layer. So, vertical stratification and location of heat are two different things.

Breaking waves on an interface due to a shear instability, i.e., flow in the (fresh and cold) upper layer is less than the flow in the denser (warm and salty) lower layer.

Second, think of ocean stratification as a blanket that insulates one region from the other. Removing the blanket requires kinetic energy (something or someone has to do the work, doing work requires energy). As you melt freshwater ice via conduction of heat to the ice, the melt has zero salinity and a temperature at the freezing point. This zero salinity water acts as the insolation blanket that reduces the heat reaching the ice. So, again, you need (a) a source of kinetic energy to do work to break down the stratification (of salinity) to (b) enable the transfer of heat from the ocean to the ice.

6. Can you recommend any key journal papers you think we should read?

The classical paper on this subject is [Gade, H.G., 1979: Melting of ice in sea water: A primitive model with application to the Antarctic Ice Shelf and Icebergs. J. Phys. Oceanogr., 9, 189-198], but this paper is a thorough theoretical development. I have professors of glaciology asking me what it means, so the material is not easy to penetrate. In a 2011 publication on the oceanography of Petermann Fjord impacting this Glacier, we made extensive use of the arguments and concepts presented in Gade (1979). That publication is more readable and accessible.

Its first author is Dr. Helen Johnson at Oxford University with whom I have collaborated since 2003 aboard US and Canadian icebreakers. She also published an illustrated diary of our 2007 expedition to Nares Strait.

ADDED Jan-12: My mind yesterday was unclear on the in situ temperature at which glacier ice of zero salinity is melting in seawater such as found on the Labrador shelf. The comment below points this out concisely, while this link to TheNakedScientist perhaps provides the longer and more visual explanation. Another fun explanation of the melting and freezing of ice in a salt solution relates to the making of ice cream. A subsurface temperature at -1.5 C at a salinity of 33.5 psu such as found on the Labrador shelf does melt the zero salinity ice of the iceberg somewhat. A boundary layer consisting of fresh meltwater will lower the salinity adjacent to the iceberg which will increase the freezing point which will reduce the melting until a new stable equilibria is reached.

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Ice Drift from Nares Strait to Newfoundland: The 1871 Polaris Expedition and Petermann Ice Islands

Posted on January 10, 2012 | Leave a comment

“Nineteen ship-wrecked members of the Polaris expedition of 1871-72
drifted on ice floes a distance of over 2500 km from Nares Strait near
79°N latitude to Newfoundland. Surviving this six months long ordeal,
they inadvertently mapped for the first time a drift of icy waters
from the Arctic to the North Atlantic Ocean. That they survived to
tell the tale is tribute to two Inuit, Joe Ebierbing and Hans Hendrik,
whose hunting skills and diligence provided food for the entire party
(Hendrik, 1878). Almost a century later, 1962-64, ice island WH-5 was
carefully tracked via ships and aircraft from north of Ellesmere
Island (83°N) to the Atlantic via Nares Strait (Nutt, 1966). The
movements of ice and water so revealed are one link in the global
hydrological cycle whose significance to global climate has yet to be
understood …” [from Muenchow et al. (2007)]

'Captain Hall's Arctic Expedition -- The "Polaris"'', a wood engraving published in ''Harper's Weekly'', May 1873.

The BBC contacted me this morning asking great questions related to the Petermann Ice Islands and icebergs. These reminded me of the opening paragraph quoted from a paper on the oceanography of Nares Strait. I published it in 2007 with two friends and fellow sailors of icy waters, Kelly Falkner and Humfrey Melling. In 2003 we sailed together on the US Coast Guard icebreaker Healy and making detailed measurements on ice, water,and bottom sediments. We reported strong southward currents from the Arctic Ocean into Baffin Bay opposing the local winds. Ocean currents were particular strong about 100 meters below the surface on the Canadian coast of Nares Strait. I am still working on these data as they relate to the flux of fresher Arctic waters into the Atlantic Ocean and their climate impacts.

There is history and drama in these places: Hall Basin is named after the leader of the Polaris Expedition, Charles Francis Hall, an American who was likely poisoned in 1871 with arsenic by his German Chief Scientist Dr. Emil Bessel aboard the Polaris beset in ice in Hall Basin. Bessel has a tiny fjord off Greenland named after him, it is located about 10 miles south of Petermann Fjord, named after August Heinrich Petermann, a German cartographer who traveled little himself but mapped much of what others had traveled. Joe Island, named after the Inuit hunter Joe Ebierbing of the Polaris ice drift, is the island that broke the 2010 Petermann Ice Island at the entrance of Petermann Fjord into PII-A and PII-B. The second Inuit hunter of the infamous 1872 drift, Hans Hendrick has Hans Island named after him which is very much in the center of Nares Strait and is currently claimed by both Canada and Denmark.

The Wikipedia entry on the Polaris Expedition has a well-written introduction while the book by Pierre Berton”The Arctic Grail”provides the story along with many other foolish and professional travails to reach the North Pole during the 19th and early 20th centuries.

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Petermann Ice Island(s) 2010 through 2011, Part-1

Posted on January 6, 2012 | 1 Comment

An ice island 4 times the size of Manhattan spawned from a remote floating glacier in north-western Greenland the first week in August of 2010, but it quickly broke into at least 3-4 very large pieces as soon as it flowed freely and encountered smaller, but real and rocky islands. A beacon placed on the ice transmit its location several times every day. It shows a rapid transit from the frigid, ice-infested Arctic waters off Canada’s Ellesmere, Devon, and Baffin Islands to the balmier coasts of Labrador and Newfoundland:

Track of Petermann Ice Island from Aug.-2010 through Aug.-2011 traveling in shallow water from northern Greenland along Baffin Island and Labrador to Newfoundland.

Initial progress was slow as it took the new ice island almost 30 days to wiggle itself free of the narrow constraints of Petermann Fjord:

Petermann Glacier discharges its large ice island into Nares Strait on Aug.-30, 2010.

As soon as it left its home port, it hit broke hit tiny Joe Island on Sept.-9, 2010 and broke into two pieces, PII-A and PII-B for Petermann Ice Island A and B. Not a good start for a new island setting out to sail all the way to Newfoundland where PII-A arrived a year later, but I am getting ahead of my story.

Petermann Ice Island breaks into two segments on Sept.-9, 2010 as seen in this radar image provided by the European Space Agency. Greenland is at the bottom right, Canada top left, the Arctic Ocean is at the top right.

Once in Nares Strait both ice islands experienced a very strong and persistent ocean current. PII-A, about 1.5 the size of Manhattan went first followed by the larger (about 2.5 Manhattans) and thicker PII-B. Their tracks follow each other closely and they almost kiss on Oct.-8, 2010 when both are caught in the same eddy or meander of a prominent coastal current flowing south along Ellesmere and Devon Islands.

Pieces of Petermann Ice Island on Oct.-8, 2010 off southern Ellesmere Island about 600-km to the south of their origin. RadarSat imagery is courtesy of Luc Desjardins of the Canadian Ice Service, Government Canada.

Within a week the larger 136 km^2 piece PII-B breaks into three pieces of 93.5, 28.9, and 11.3 km^2 by Oct.-16 while PII-A stays largely intact at 73.6 km^2. These are all very large islands, the land area of Manhattan is about 60 km^2 for comparison. Some of these pieces approach the coast, some become grounded for a few days to a few weeks, some break off smaller pieces and spawn massive ice bergs that are not always visible from space. PII-A enters Lancaster Sound a week ahead of PII-B on Nov.-14, but exits it within 2 weeks:

Multiple pieces spawned from Petermann Ice Island as seen by RadarSat on Nov.-26 and Nov.-28, 2010 composited and anotated by Luc Desjardins of the Canadian Ice Service, Government Canada.

Notice also the evolution of a string of segments that Luc Desjardins of the Canadian Ice Service identified as pieces from Petermann Glacier. Glacier ice has a darker radar backscatter signature than the sea ice around it. All these pieces eventually enter the Baffin Island Current, a prominent large ocean current that extends from the surface to about 200-300 m depth. The Petermann pieces are moved mostly by ocean currents, not winds, because there is more drag on the submerged pieces of the 40-150 meter thick glacier ice. In contrast, the much thinner sea ice is mostly driven by the winds. This is also the reason one often finds areas in the lee of icebergs and islands free of older ice which is swept away by the winds as the iceberg moves slower as it is driven by deeper ocean currents. I will talk more of these in a later post.

As part of a large oceanography program in northern Baffin Bay and Nares Strait in 2003, we collected ocean temperature, salinity, chemistry, and current data along lines roughly perpendicular to both Baffin Island in the west and Greenland in the east along with the trajectory of PII-A in the fall of 2010 (red dots) and the almost identical track of a much smaller ice island from Petermann Glacier that passed the area in 2008:

Map of the study area with trajectory of a 2010 (red) and 2008 (grey) beacons deployed on Petermann Glacier ice islands over topography along with CTD station locations (circles) and thalweg (black line). Nares Strait is to the north of Smith Sound.

I will talk about these data and the subsequent tracks of PII-A and PII-B from 2010 into 2011 in Part-2 of this summary on how the first of this piece (PII-A) arrived off coastal Newfoundland in the late summer of 2011. Rest assured that there are many more pieces coming to coastal Labrador and Newfoundland in 2012 and 2013 where they put on a majestic display of abundant icebergs such as this last remnant of PII-A as seen from the air on Nov.-2, 2011 in Notre Dame Bay, Newfoundland.

Last surviving fragments of PII-A on Nov.-2, 2011 from a survey by air of southern Notre Dame Bay conducted by Canadian Ice Service, Government Canada..

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Ice Arch off North-West Greenland Locks Ice Motion in Nares Strait

Posted on December 13, 2011 | Leave a comment

Winter has come to north-west Greenland as the sea ice of Nares Strait has locked itself to land and stopped movement of all ice from the Arctic Ocean in the north to Baffin Bay and the Atlantic Ocean in the south. While there is no sunlight for several more months now during the polar night, the warm ocean beneath the ice emits heat through the ice which becomes visible to heat-sensing satellites. The light yellow and reddish colors show thin ice while the darker bluish colors show thicker ice today:

Dec.-13, 2011 surface brightness temperature of Nares Strait showing an ice arch in Smith Sound separating thin and moving ice (reddish, yellow) from thick land-fast ice (blue).

The prior 2010/11 winter was the first in several years that these normal conditions have returned. The ice arch in Smith Sound did not form in 2009/10, 2008/09, and 2007/08 winters while a weak arch in 2007/08 fell apart after only a few days. Conditions in 2009 were spectacular, as only a northern ice arch formed. Since the ocean moves from north to south at a fast and steady clip, it kept Nares Strait pretty clear of ice for most of the winter as no Arctic ice could enter these waters and all locally formed new “first-year ice” is promptly swept downstream:

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

The very thin and mobile ice in Nares Strait of 2009 exposed the ocean to direct atmospheric forcing for the entire year. I reported substantial warming of ocean bottom temperatures here during this period. This new 2011/12 ice arch formed the last few days. If it consolidates during the next weeks, then it is very likely to stay in place until June or July of 2012. It decouples the ocean from the atmosphere and, perhaps more importantly, prevents the Arctic Ocean from losing more of its oldest, thickest, and hardest sea ice. This is very good news for the Arctic which has lost much ice the last few years.

For more daily thermal MODIS imagery take a peek at http://muenchow.cms.udel.edu/Nares2011/Band31/ for 2011. Replace Nares2011 with Nares2003 or any other year, and an annual sequence appears. Furthermore, my PhD student Patricia Ryan just sent me a complete list of files that I need to process until 2017. Fun times.

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New Ice Island Forming at Pine Island Glacier, Antarctica

Posted on November 4, 2011 | 2 Comments

A new ice island is about to form as spring and summer arrive in Antarctica. NASA researchers working on Pine Island Glacier (PIG) as part of the IceBridge Mission discovered a 30 km wide rift some 25 km from the ocean during overflights in a DC-8 research aircraft.The rift will eventually will break off into a tabular iceberg about 10 times the size of Manhattan. The rift is wide enough to be visible in optical satellite imagery that has a spatial resolution of 250 meters. A BBC report credits NASA scientist stating that this large calving of an ice island is part of a natural, roughly decadal cycle.

Pine Island Glacier from MODIS/Terra with crack visible at 250-m spatial resolution.

A crack runs across the floating ice shelf of Pine Island Glacier in Antarctica, seen from NASA's DC-8 on Oct. 14, 2011. Credit: Michael Studinger/NASA

Antarctic massive ice sheets contain 70% of all freshwater and 90% of all ice on earth. Most of this is contained within the stable East Antarctic ice sheet where temperatures have increased little. In contrast, the West Antarctic ice sheet has seen warming by about 0.2 degrees Celsius and a net loss of ice to raise global sea level by perhaps 2-3 inches in 100 years. The grounding line Pine Island Glacier (where ocean, bedrock, and ice meet) has retreated for several decades as warmer ocean waters near the bottom cross a sill and plunge into a landward depression of the bedrock. This leads to enhanced melting of the floating ice-sheet and a potential instability that could lead to a collapse of the ice-shelf and much enhanced discharge of the Pine Island Glacier to draw down a large fraction of the West Antarctic Ice Sheet.

Bottom topography under Pine Island Glacier and grounding line. Blue colors show greater depths and its connection to the open ocean (bottom, north). (credit: NASA)

A similar physical process, albeit at a smaller scale, is potentially working at Petermann Glacier off Greenland where the grounding line is at a local maximum of bedrock elevation. Petermann’s grounding line has probably not moved substantially the last 100 years or so.

More detail on the evolving Pine Island Glacier, Antarctica event can be found at a NASA media briefing.

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Posted in Global Warming, Ice Island

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