Tag Archives: GPS

Preparing Ocean Work outside Thule Air Base

Posted on March 6, 2017 by | 5 comments

I am heading to North Greenland in 3 days time to work where temperatures will be close to -20 F. The ocean is covered by 3-4 feet of sea ice that is frozen to land. We will drill lots of ice holes to deploy ocean sensors that will connect via cables to weather stations and satellite phone. Fancy $20,000 GPS units will measure the tides across the fjord and provide a group of future Naval officers a reference for their fancy electronic gear to measure sea ice thickness remotely by walking and comparing results to those obtained from planes overhead. Cool and cold fun.

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The ocean pier at Thule Air Base in Greenland in March 2017. The view is towards the north-west along my proposed mooring line [Photo Credit: Sean Baker]

There has been much packing and shipping the last weeks, about 2300 lbs to be precise,which made my body stiff and sore. Another way to hurt my aging body was to learn shotgun shooting for the unlikely polar bear encounter on the sea ice. My shoulder still hurts from the recoil blasts of the 12 gauge pump-action gun with 3” long cartridges that included a 1 oz. lead slug. I also tested a cot and sleeping bag that will be with me on the ice for emergencies. The night in my garden a few days ago was cozy, but the cot required an insulation mattress, as it was too close to the ground. It was rough sleeping, because of unexpected noises not cold, but I did sleep some and woke up when the sun came up.

Cot, air mattress, and down sleeping bag testing in my garden after a rough night.

Cot, air mattress, and down sleeping bag testing in my garden after a rough night.

The clear skies over Thule during the 2 weeks that the sun is up again also gave me the first Landsat image. It shows the landfast sea ice, but it also shows its very limited extend as very thin ice and perhaps even open water occurs while the winds blow along the coast from the north. This cold wind moves the mobile sea ice offshore to the west thus opening up the oceans that will promptly freeze, however, the back ocean still shows under the inch-thin new ice:

Wolstenholme Fjord as seen by LandSat on Feb.-27, 2017. The line with the red dots extends from Thule pier seaward towards the north-west. Note the dark spot near the left-top corner that shows thin new ice or even open water. White contours are ocean depths in meters.

Wolstenholme Fjord as seen by LandSat on Feb.-27, 2017. The line with the red dots extends from Thule pier seaward towards the north-west. Note the dark spot near the left-top corner that shows thin new ice or even open water. White contours are ocean depths in meters.

This thin new ice is the limit of where I expect to be working. After measuring ice thickness directly via drilling through the ice, my first measurement will be that of how temperature and salinity varies from under the ice to the bottom of the ocean.

Working on the sea ice off northern Greenland [Photo credit, Steffen Olsen]

Working on the sea ice off northern Greenland [Photo credit, Steffen Olsen]

Danish friends do this routinely about 60 miles to the north where they work out of the Inughuit community of Qaanaaq, but Inglefield Fjord is much deeper and connects to warm Atlantic waters from the south that, I believe, we do not have in Wolstenholme Fjord. Hence I expect much less heat inside Wolstenholme Fjord and perhaps a different response of three glaciers to ocean forcing. This theory does not help me much as I will have to lower instruments via rope and a winch into the water. How to attach rope to instruments and winch? Knots.

I am very poor at making knots as my hand-eye co-ordination and memory is poor. So I spent some time this week to learn about knots such as

that should work on my braided Kevlar lines that I connect to shackles

Fancy knots on shackles in my home office ... yes, Peter Freuchen is on the bookshelf, too.

Fancy knots on shackles in my home office … yes, Peter Freuchen is on the bookshelf, too.

There are always devils in the many details of field work. Another worry is that my 10” ice-drill is powered by 1 lbs bottles of propane. It is not possible to send these camping propane canisters via air, but larger 20 lbs tanks exist in Thule for grill cooking at the NSF dormitory where I will be staying. So I also will have to learn how to fill the smaller container from the large one. Just ordered another adaptor from Amazon to travel with me on my body to do this.

I am both terribly nervous and excited about the next 6 weeks. This is my first time working on the ice, because before I have always been on icebreakers in summer. These past Arctic summer expeditions on ships created an unreal and distant connection that, I hope, will be shattered by this spring. I will get closer to the cold and icy seas that are my passion. Oceanography by walking on water … ice.

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Posted in Greenland, Ice Cover, Oceanography, sea ice, Thule

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The Ice Shelf of Petermann Gletscher and its Ocean Below: Descriptions

Posted on April 11, 2016 by | 1 comment

“In 1921 owing to starvation I had to go directly from Cape Heiberg-Juergensen to our cache at Cape Agassiz … during this journey the greater part of the glacier was mapped.” –Lauge Koch, 1928

Petermann Fjord connects Petermann Gletscher to Nares Strait which in turn is connected to the Arctic Ocean in north and the Atlantic Ocean in the south (Figure-2). The track of Petermann ice island PII-2010A emphasizes this connection as the 60 meter thick section of the ice island reaches the Labrador Sea in the south within a year after its calving in 2010.

TOS2016-Fig2

PII-2010 left Petermann Fjord on the 9th of September in 2010 when it broke into segments A and B while pivoting around a real island. It flushed out of Nares Strait 10 days later when an ice-tracking beacon was placed to track the ice island. The ~60 m thick segment PII-2010A moved southward with the Baffin Island Current (Münchow et al., 2015) at an average speed of ~ 0.11 m/s past Davis Strait. Remaining on the continental shelf of the Labrador Sea, it passed Boas’ Cumberland Sound, Labrador, and reached Newfoundland in August 2011 when it melted away in a coastal cove about 3000 km from Petermann Fjord (Figure-2).

TOS2016-Fig7

Petermann Gletscher drains about 4% of the Greenland ice sheet via a network of channels and streams that extend about 750 km landward from the grounding line (Bamber et al., 2013). The glacier goes afloat at the grounding zone where bedrock, till, and ice meet the ocean waters about 600 meter below sea level (Rignot, 1996).

TOS2016-Fig3

Figure-3 shows a section of surface elevation from a laser altimeter flown on a repeat path along the glacier in April 2013 and May 2014 as part of NASA’s Operation IceBridge. Assuming hydrostatic balance, we also show basal topography below the sea surface that varies from 200 meters at the terminus to 600 meters at the grounding zone near distance zero (Figure-3). The 2013 profile has been shifted seaward by 1.25 km to match the terminus position. Note the close correspondence of large and small crevasses in 2013 and 2014 near 20, 40, and 45 km from the grounding zone.

The seaward shift of the 2013 relative to the 2014 profile implies a uniform glacier speed of about 1180 meters per year. This value is almost identical to the 1170 meters per year that we measure between 20th August of 2015 and 11th February of 2016 with a single-frequency GPS placed about 13 km seaward of the grounding zone as part of the ocean weather observatory.

We compare 2013/14 and 2015/16 velocity estimates in Figure-3 with those obtained from RadarSat interferometry between 2000 and 2008 (Joughin et al., 2010) of which I here only show three:

Figure-3 shows that glacier speeds before 2010 are stable at about 1050 m/y, but increased by about 11% after the 2010 and 2012 calving events. This increase is similar to the size of seasonal variations of glacier motions. Each summer Petermann Gletscher speeds up, because surface meltwater percolates to the bedrock, increases lubrication, and thus reduces vertical friction (Nick et al., 2012). Figure 3 presents summer velocity estimates for August of 2015 from three dual-frequency GPS. The along-glacier velocity profiles measured by these geodetic sensors in the summer follow the shape of the 2000 to 2008 winter record, however, its speeds are about 10% larger and reach 1250 m/y near the grounding zone (Figure 3).

Uncertainty in velocity of these GPS systems is about 1 m/y which we estimate from two bed rock reference stations 82 km apart. Our ice shelf observations are referenced to one of these two semi-permanent geodetic stations. Its location at Kap Schoubye is shown in Figure-1. Data were processed using the GAMIT/TRACK software distributed by MIT following methodology outlined by King (2004) to archive vertical accuracy of 2-3 centimeters which, we show next, is small relative to tidal displacements that reach 2 meters in the vertical.

TOS2016-Fig4

Figure-4 shows the entire 13 day long record of vertical glacier displacement from 30 seconds GPS measurements in August of 2015. The observed range of vertical glacier displacements diminishes from almost 2 meters about 26 km seaward of the grounding zone (GZ+26) via 0.6 meters in the grounding zone (GZ-00) to nil 20 km landward of the grounding zone (GZ-20). Anomalies of horizontal displacement are largest at GZ-00 with a range of 0.2 m (not shown) in phase with vertical oscillations (Figure-4).

More specifically, at GZ+26 we find the ice shelf to move up and down almost 2 meters roughly twice each day. This is the dominant semi-diurnal M2 tide which has a period of 12.42 hours. Notice that for each day there is also a diurnal inequality in this oscillation, that is, the two maximal (minimal) elevations oscillate from a higher to a lower High (Low) water. This is the diurnal K1 tide which has a period of 23.93 hours. And finally, all amplitudes appear modulated by some longer period that appears close to the record length of almost two weeks. This is the spring-neap cycle that is caused by a second semi-diurnal S2 tide that has a period of 12.00 hours. A formal harmonic analysis to estimate the amplitude and phases of sinusoidal oscillations at M2, K1, S2 and many more tidal constituents will be published elsewhere for both Petermann Fjord and Nares Strait. Preliminary results (not shown) reveal that the amplitudes and phases of the tidal signals at GZ+26 are identical to those observed off Ellesmere Island at 81.7 N latitude in both the 19th (Greely, 1888) and 21st century.

Hourly tidal observations at Discovery Harbor taken for 15 days by Greely in 1881 and Peary in 1909.

Hourly tidal observations at Discovery Harbor taken for 15 days by Greely in 1881 and Peary in 1909.

In summary, both historical and modern observations reveal real change in the extent of the ice shelf that moves at tidal, seasonal, and interannual time scales in response to both local and remote forcing at these times scales. Future studies will more comprehensively quantify both the time rate of change and its forcing via formal time series analyses.

P.S.: This is the second in a series of four essays that I am currently developing into a peer-reviewed submission to the Oceanography Magazine of the Oceanography Society. The work is funded by NASA and NSF with grants to the University of Delaware.

References:

Bamber, J.L., M.J. Siegert, J.A. Griggs, S. J. Marshall, and G. Spada. 2013. Palefluvial mega-canyon beneath the central Greenland ice sheet. Science 341: 997-999.

Greely, A.W. 1888. Report on the Proceedings of the United States Expedition to Lady Franklin Bay, Grinnell Land. Government Printing Office, Washington, DC.

Joughin, I., B.E. Smith, I.M. Howat, T. Scambos, and T. Moon. 2010. Greenland flow variability from ice-sheet wide velocity mapping. Journal of Glaciology 56 (197): 415-430.

King, B. 2004. Rigorous GPS data-processing strategies for glaciological applications. Journal of Glaciology 50 (171): 601–607.

Münchow, A., K.K. Falkner, and H. Melling. 2015. Baffin Island and West Greenland current systems in northern Baffin Bay. Progress in Oceanography 132: 305-317.

Nick, F.M., A. Luckman, A. Vieli, C.J. Van Der Veen, D. Van As, R.S.W. Van De Wal, F. Pattyn, A.L. Hubbard, and D. Floricioiu. 2012. The response of Petermann Glacier, Greenland, to large calving events, and its future stability in the context of atmospheric and oceanic warming. Journal of Glaciology 58 (208): 229-239.

Rignot, E. 1996. Tidal motion, ice velocity and melt rate of Petermann Gletscher, Greenland, measured from radar interferometry. Journal of Glaciology 42 (142): 476-485.

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Posted in Greenland, Ice Island, Oceanography, Petermann Glacier, Petermann2015, Polar Exploration

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The Ice Shelf of Petermann Gletscher, North Greenland and its ocean below: Introductions

Posted on March 29, 2016 by | 3 comments

“In 1921 owing to starvation I had to go directly from Cape Heiberg-Juergensen to our cache at Cape Agassiz … during this journey the greater part of the glacier was mapped.” — Lauge Koch, 1928

Traveling by dog sled, Geologist Lauge Koch mapped Petermann Gletscher in 1921 after he and three Inuit companions crossed it on a journey to explore northern North Greenland. They discovered and named Steensby, Ryder, and H.C. Ostenfeld Glaciers that all had floating ice shelves as does Petermann (Ahnert, 1963; Higgins, 1990). In Figure 1 I reproduce the historic map of Koch (1928) that also contains his track in in 1917 and 1921 both across the terminus and across its upstream ice stream. In 1921 all four starved travelers returned safely after living off the land. Four years earlier, however, they were not so lucky: two traveling companions died on a similar journey in 1917 (Rasmussen, 1923).

Maps of Petermann Gletscher by Lauge Koch from 1917 and 1921 dog sleds and 2015 from MODIS-Terra.

Only 20 years after Lauge Koch’s expeditions by dog sled, air planes and radar arrived in North Greenland with the onset of the Cold War. The Arctic Ocean to the north became a battle space along with its bordering land and ice masses of northern Greenland, Ellesmere Island, Canada, Alaska, and Siberia. Weather stations were established in 1947 at Eureka by aircraft and in 1950 at Alert by US icebreaker to support military aviation (Johnson, 1990). In 1951 more than 12,000 US military men and women descended on a small trading post called Thule that Knud Rasmussen and Peter Freuchen had established 40 years earlier to support their own and Lauge Koch’s dog-sled expeditions across Greenland (Freuchen, 1935). “Operation Blue Jay” built Thule Air Force Base as a forward station for fighter jets, nuclear armed bombers, and early warning radar systems. The radars were to detect ballistic missiles crossing the Arctic Ocean from Eurasia to North America while bombers were to retaliate in case of a nuclear attack from the Soviet Union.

An F-102 jet of the 332d Fighter-Interceptor Squadron at Thule AFB in 1960. [Credit: United States Air Force]

An F-102 jet of the 332d Fighter-Interceptor Squadron at Thule AFB in 1960. [Credit: United States Air Force]

About another 60 years later, the jets, the bombers, and the communist threat were all gone, but the Thule Air Force Base is still there as the gateway to North Greenland. It is also the only deep water port within a 1,000 mile radius where US, Canadian, Danish, and Swedish ships all stop to receive and discharge their crews and scientists. Since 2009 Thule AFB also serves as the northern base for annual Operation IceBridge flights over North Greenland to map the changing ice sheets and glaciers.

The establishment of military weather stations and airfields in the high Arctic coincided with the discovery of massive ice islands drifting freely in the Arctic Ocean. On Aug.-14, 1946 airmen of the 46th Strategic Reconnaissance Squadron of the US Air Force discovered a moving ice islands with an area of about 200 square that was kept secret until Nov.-1950 (Koenig et al, 1950). Most of these ice islands originated from rapidly disintegrating ice shelves to the north of Ellesmere island (Jeffries, 1992; Copland 2007), however, the first historical description of an ice islands from Petermann Gletscher came from Franz Boas in 1883 who established a German station in Cumberland Sound at 65 N latitude and 65 W longitude as part of the first Polar Year.

Petermann Ice Island of 2012 at the entrance of Petermann Fjord. The view is to the north-west with Ellesmere Island, Canada in the background. [Photo Credit: Jonathan Poole, CCGS Henry Larsen]

Petermann Ice Island of 2012 at the entrance of Petermann Fjord. The view is to the north-west with Ellesmere Island, Canada in the background. [Photo Credit: Jonathan Poole, CCGS Henry Larsen]

Without knowing the source of the massive tabular iceberg the German physicist Franz Boas reported detailed measurements of ice thickness, extend, and undulating surface features of an ice island in Cumberland Sound that all match scales and characteristics of Petermann Gletscher (Boas, 1885). These characteristics were first described by Dr. Richard Croppinger, surgeon of a British Naval expedition in 1874/75 (Nares, 1876). Dr. Croppinger identified the terminus of Petermann Gletscher as a floating ice shelf when he noticed vertical tidal motions of the glacier from sextant measurements a fixed point (Nares, 1876). His observations on tides were the last until a group of us deployed 3 fancy GPS units on the glacier last summer.

These fancy GPS receivers give centimeter accuracy vertical motions at 30 second intervals. Here is what the deployment of 3 such units in August of 2015 gives me:

Vertical (top) and horizontal (bottom) motion of Petermann Gletscher from GPS referenced to a GPS base station on bed rock at Kap Schoubye. Note the attenuation of the tide from 26 km sea ward of the grounding line (red) to at the grounding line (black) and 15 km landward of the grounding line (blue). The horizontal location motion has the mean motion removed to emphasize short-term change over the much, much larger forward motion of the glacier that varies from about ~700 (black) to ~1250 meters per year (red).

Vertical (top) and horizontal (bottom) motion of Petermann Gletscher from GPS referenced to a GPS base station on bed rock at Kap Schoubye. Note the attenuation of the tide from 26 km sea ward of the grounding line (red) to at the grounding line (black) and 15 km landward of the grounding line (blue). The horizontal location motion has the mean motion removed to emphasize short-term change over the much, much larger forward motion of the glacier that varies from about ~700 (black) to ~1250 meters per year (red).

We have indeed come a far way during the last 150 years or so. Mapping of remote landscape and icescape by starvation and dog-sled has been replaced by daily satellite imagery. Navigation by sextant and a mechanical clock has been replaced by GPS and atomic clock whose errors are further reduced by a local reference GPS. These fancy units and advanced data processing allow me to tell the vertical difference between the top of my iPhone sitting on a table in my garden from the table.

Working at in the garden at home preparing for field work.

Working at in the garden at home preparing for field work near Petermann Fjord.

P.S.: This is the first in a series of essays that I am currently developing into a peer-reviewed submission to the Oceanography Magazine of the Oceanography Society. The work is funded by NASA and NSF with grants to the University of Delaware.

Ahnert, F. 1963. The terminal disintegration of Steensby Gletscher, North Greenland. Journal of Glaciology 4 (35): 537-545.

Boas, F. 1885. Baffin-Land, geographische Ergebnisse einer in den Jahren 1883 und 1884 ausgeführten Forschungsreise. Petermann’s Mitteilungen Ergänzungsheft 80: 1-100.

Copland, L., D.R. Mueller, and L. Weir. 2007. Rapid loss of the Ayles Ice Shelf, Ellesmere Island, Canada. Geophysical Research Letters 34 (L21501): doi:10.1029/2007GL031809.

Freuchen, P. 1935. Arctic adventures: My life in the frozen North. Farrar & Rinehard, NY, 467 pp.

Higgins, A.K. 1990. North Greenland glacier velocities and calf ice production. Polarforschung 60 (1): 1-23.

Jeffries, M. 1992. Arctic ice shelves and ice islands: Origin, growth, and disintegration, physical characteristics, structural-stratigraphic variability, and dynamics. Reviews of Geophysics 30 (3):245-267.

Johnson, J.P. 1990. The establishment of Alert, N.W.T., Canada. Arctic 43 (1): 21-34.

Koch, L., 1928. Contributions to the glaciology of North Greenland. Meddelelser om Gronland 65: 181-464.

Koenig, L.S., K.R. Greenaway, M. Dunbar, and G. Hattersley-Smith. 1952. Arctic ice islands. Arctic 5: 67-103.

Münchow, A., K.K. Falkner, and H. Melling. 2015. Baffin Island and West Greenland current systems in northern Baffin Bay. Progress in Oceanography 132: 305-317.

Münchow, A., L. Padman, and H.A. Fricker. 2014. Interannual changes of the floating ice shelf of Petermann Gletscher, North Greenland, from 2000 to 2012. Journal of Glaciology 60 (221): doi:10.3189/2014JoG13J135.

Nares, G. 1876. The official report of the recent Arctic expedition. John Murray, London,

Rassmussen, K., 1921: Greenland by the Polar Sea: the Story of the thule Expedition from Melville Bay to Cape Morris Jessup, translated from the Danish by Asta and Rowland Kenney, Frederick A. Stokes, New York, NY, 327 pp.

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Posted in Arctic Glacier, Greenland, History, Ice Island, Petermann2015, Polar Exploration

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Thule, Greenland in Sharp Focus

Posted on March 25, 2016 by | 1 comment

I want to fly like an eagle
To the sea
Fly like an eagle
Let my spirit carry me

Steve Miller Band, 1976

The eagle “sees” the ground, because the twinkling sensation of light tickles her nerves. Today’s cameras work without the twinkle and tickle. They store numbers (digits) that approximate the amount of light passing through the lens. Satellite sensors work the same way. The data they beam to earth give me the soaring feeling of flying like an eagle, but there is more to the bits and bytes and digits sent home from space to our iPhones, laptops, and the internet.

Aerial photo taken Oct.-13, 1860 of Boston, MA by J.W. Black.

Aerial photo taken Oct.-13, 1860 Boston, MA from a balloon by J.W. Black.

The Metropolitan Museum of Art in New York houses the earliest existing aerial photo that was taken from a balloon hovering 600 meters above Boston, Massachusetts. Within a year the American Civil War broke out and this new technology became an experimental tool of war. It advanced rapidly, when air craft replaced the balloon during the First World War. Sharp photos of bombed-out battle and killing fields along the entire Western Front in France were taken by both Allied and German soldiers every day. Placing these photos on a map for efficient analyses of how a land- sea- or ice-scape changes over time, however, was impossible, because photos do not record precise locations.

Modern satellite photos are different. We now have fancy radar beams, computers, and several Global Position Systems (GPS) with atomic clocks to instantly calculation satellite tracks every second. This is why we now can both take photos from space AND map every dot or pixel that is sensed by the satellite moving overhead at 17,000 miles an hour snapping pictures from 430 miles above. The camera is so good that it resolves the ground at about 45 feet (15 meters). This is what such a (LandSat) picture looks like

LandSat photo/map of Thule, Greenland Mar.-17, 2016. The airfield of Thule Air Force Base is seen near the bottom on the right. The island in ice-covered Westenholme Fjord is Saunders Island (bottom left) while the glacier top right is Chamberlin Gletscher.

LandSat photo/map of Thule, Greenland Mar.-17, 2016. The airfield of Thule Air Force Base is seen near the bottom on the right. The island in ice-covered Westenholme Fjord is Saunders Island (bottom left) while the glacier top right is Chamberlin Gletscher.

Everyone can download these photos from the United States Geological Survey which maintains a wonderful photo and data collection archive at

http://earthexplorer.usgs.gov

but the tricky part is to turn these images or photos into maps which I have done here. More specifically, I wrote a set of c-shell and nawk scripts along with Fortran programs on my laptop to attach to each number for the light sensed by the satellite (the photo) another two numbers (the map). These are latitude and longitude that uniquely fix a location on the earth’s surface. A “normal” photo today has a few “Mega-Pixels,” that is, a few million dots. Each scene of LandSat, however, has about 324 million dots. This is why you can discern both the runways of Thule Air Force Base at 68 degrees 45′ West longitude and 76 degrees 32′ North latitude. The pier into the ice-covered ocean is just a tad to the south of Dundas Mountain at 68:54′ W and 76:34′ N. A scale of 5 kilometers is shown at the top on the right. For spatial context, here is a photo of the pier with the mountain in the background, that is, the object shown in the photo such as mountain, ship, and Helen serves a rough, but imprecise reference:

Dr. Helen Johnson in August 2009 on the pier of Thule AFB with CCGS Henry Larsen and Dundas Mountain in the background. [Credit: Andreas Muenchow]

Dr. Helen Johnson in August 2009 on the pier of Thule AFB with CCGS Henry Larsen and Dundas Mountain in the background. [Credit: Andreas Muenchow]

This photo shows the airfield and Saunders Island

Thule AFB with its airport, pier, and ice-covered ocean in the summer. The island is Saunders Island. The ship is most likely the CCGS Henry Larsen in 2007. [Credit: Unknown]

Thule AFB with its airport, pier, and ice-covered ocean in the summer. The island is Saunders Island. The ship is most likely the CCGS Henry Larsen in 2007. [Credit: Unknown]

The satellite image of the ice-covered fjord with Thule, Saunders Island, and Chamberlin Gletschers shows a richly texture field of sea ice. The sea ice is stuck to land and not moving except in the west (top left) where it starts to break up as seen by the dark gray piece that shows ‘black’ water peeking from below a very thin layer of new ice. There is also a polynya at 69:15′ W and 76:39′ N just to the south of an island off a cape. A polynya is open water that shows as black of very dark patches. A similar albeit weaker feature also shows to the east of Saunders Island, but it is frozen over, but the ice there is not as thick as it is over the rest of Westenholme Fjord. I suspect that larger tidal currents over shallow water mix ocean heat up to the surface to keep these waters covered by water or dangerously thin ice. There are also many icebergs grounded in the fjord. They cast shadows and from the length of these shadows one could estimate their height. Here is another such photo from 2 days ago:

LandSat photo/map of Thule, Greenland Mar.-21, 2016. The airfield of Thule Air Force Base is seen near the bottom on the right. The island in ice-covered Westenholme Fjord is Saunders Island (bottom left) while the glacier top right is Chamberlin Gletscher.

LandSat photo/map of Thule, Greenland Mar.-21, 2016. The airfield of Thule Air Force Base is seen near the bottom on the right. The island in ice-covered Westenholme Fjord is Saunders Island (bottom left) while the glacier top right is Chamberlin Gletscher.

I am using the satellite data and maps here to plan an experiment on the sea ice of Westenholme Fjord. Next year in March/April I will lead a team of oceanographers, engineers, and acousticians to place and test an underwater network to send data from the bottom of the ocean under the sea ice near Saunders Island to the pier at Thule and from there on to the internet. We plan to whisper from one underwater listening post to another to communicate over long ranges (20-50 kilometers) via a network of relay stations each operating smartly at very low energy levels. We will deploy these stations through holes drilled through the landfast ice 1-2 meters thick. The work is very exploratory and is funded by the National Science Foundation. Wish us luck, as we can and will use it … along with aerial photography that we turn into maps.

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New ocean data from floating Petermann Glacier

Posted on September 25, 2015 by | 8 comments

#UDel Ocean-Weather station #Greenland on #petermann2015 calls home from 800 m under floating glacier with 2 weeks of new hourly data.

University of Delaware Ocean-Weather station on Petermann Glacier with the hot-water drilling team UDel and British Antarctic Survey after deployment Aug.-20, 2015 [Credit: Peter Washam, UDel]

University of Delaware Ocean-Weather station on Petermann Glacier with the hot-water drilling team UDel and British Antarctic Survey after deployment Aug.-20, 2015. Cables from ocean sensors emerge from the ice where the wooden cross is located on the right. [Credit: Peter Washam, UDel]

Map of Greenland's Petermann Gletscher, Fjord, and adjacent Nares Strait. The UDel Ocean-Weather station is the green dot on the floating ice shelf that does not have a red triangle. Blue dots in the ocean are where we collected ocean data from I/B Oden in August 2015. Green dots are ocean moorings which report via Iridium while red triangles are "fancy" GPS locations we instrumented for 12 days to measure vertical tidal elevations of the glacier.

Map of Greenland’s Petermann Gletscher, Fjord, and adjacent Nares Strait. The UDel Ocean-Weather station is the green dot on the floating ice shelf that does not have a red triangle. Blue dots in the ocean are where we collected ocean data from I/B Oden in August 2015. Green dots are ocean moorings which report via Iridium while red triangles are “fancy” GPS locations we instrumented for 12 days to measure vertical tidal elevations of the glacier.

My nerves are shot and I get depressed when the Ocean-Weather station does not call home when she should. We deployed the station last months on the floating section of Petermann Gletscher where she has moved steadily towards the ocean at about three meters per day. We measure this with GPS which is the black dot next to the temperature sensor above the head of the team that drilled the hole. It connected 5 ocean temperature, salinity, and pressure sensors to 800 meter depth below sea level. The data come from this great depth to the surface where it feeds into the weather station that then transmits data via an Iridium antenna to another Iridium antenna that sits atop my house. Let me run out and take a quick photo of it …

Iridium antenna atop my house in Newark, Delaware that receives data calls from Greenland.

Iridium antenna atop my house in Newark, Delaware that receives data calls from Greenland.

My problem with Iridium over the last 6 weeks has been that its (data) connectivity is spotty. For example, I received no data the last 2 weeks. This has been the longest time with no call and no new data. Designing the system, I decided against the more robust “Short-Burst-Data” SBD text messages. Instead I opted for a truly 2-way serial connection which, if a connection is established, allows more control as well as a more complete and gap-free data stream. The drawback of this serial connection via Iridium is lack of connectivity. Sometimes days or weeks go by without a successful connection even though computer codes are written to connect every 8 hours. I can change that by uploading new codes to the two Campbell CT1000 data loggers that control all sensors as well as data collection and communication via Iridium.

Today’s call was the first in two weeks, but it provided a complete data download without ANY gaps in the hourly time series of weather in the atmosphere (wind, temperature, humidity) and weather in the ocean (temperature, salinity, pressure). The ocean data show that about every 2 weeks with the spring-neap cycles, we see very large excursions of colder and fresher water appear at 2 sensors within about 30 meters of the glacier ice. It is too early to speculate on how this may relate to ocean circulation and glacier melting, but the large and frequent up and down do suggest a lot of ocean weather.

I am anxiously awaiting the next data call in about 5 hours to get the 8 hours of data. Wish me luck and a healthy Iridium satellite system where calls are about $0.90/minute. Today’s call took 5 minutes. This is what some of the (uncalibrated) data look like:

Ocean-Weather station data from Aug.-20 through Sept.-25 (today). Ocean temperatures at 5 vertical levels are shown as 5 red curves in 5th panel from top. The black lines in that panel are air temperatures that reached -20 C this week.

Ocean-Weather station data from Aug.-20 through Sept.-25 (today). Ocean temperatures at 5 vertical levels are shown as 5 red curves in 5th panel from top. The black lines in that panel are air temperatures that reached -20 C this week.

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