GPS, Geocaching, and Greenland Glaciers

Navigating ice, ocean, and land, brave women and men have always used the stars for guidance. Just think of the three kings who followed a star to witness the birth of Jesus Christ in Bethlehem 2015 years ago. They were 6 days late. Keeping track of time track was always difficult for navigating, especially at sea and the British Navy lost many ships as a result of poor time keeping. There are books written on the history of determining longitude, the best of which is called, well, “Longitude.” Now why would I ponder these questions and histories two hours before I am boarding the Swedish icebreaker Oden to travel by sea and ice to Petermann Glacier?

The Global Position System (GPS) that many of us have in our smart phones or tiny hand-held devices makes navigating easy. Both measure time as our civilization has put “stars” into space that guide hikers out in the back-country, urban dwellers to the next bar or restaurant, and missiles into a target the size of the dot over the letter “i” on a license plate of a car. Few know that the GPS satellites only sent time from an atomic clock to our GPS receivers and smart phones. Time is of the essence, there is something almost spiritual about time and how to define it. And time is linked to space not just because of Einstein’s theory of relativity, but also the way we measure space by measuring the time that waves travel through space.

Waiting for the plane to get 58 scientists to Thule to board the I/B Oden, I went for a geocaching trip an hour or two from the town of Kangerlussuaq. My wife got me into this 2 years ago as a way to explore areas via hiking without much planning. All we do is enter some GPS position of places where other people have placed “treasures” and we head out to find them. These geocaches are everywhere: within 100 feet of my home, in every city I went to in Poland, Sweden, or Germany, and now Greenland, too. My favorite GPS unit is a little hand-held $99 Garmin eTrex 10. It does a marvelous job to get me anywhere within about 3-6 feet (1-2 meters).

As part of our Petermann research, we also got four “fancy” GPS systems which we want to place on the ice shelf of Petermann Gletscher to measure tidal motions. The water under the glacier is connected to ocean that moves the Empire-State-Building thick ice up and down every 12 hours or so. We do not know by how much, though, and when it moves up and when it moves down. There should also be daily cycles and longer periods caused by winds and waves. Now these fancy $25,000 GPS are able to track over 400 satellites (not just the 9 that my Garmin does) and they receive the time information in a very raw and accurate format at more than one radio frequency in more than one way. If one has several of these, we got four, then it is possible to built a network that reduces common errors in position to a few millimeters in the horizontal, and 1-2 centimeter in the vertical after some smart processing. So these “fancy GPS” can sense the difference of the top of your smart phone from the bottom, and I do not mean its length or width, but its thin height. And this is blowing my mind. We need this accuracy to measure tides, and tides we will measure for the 20-30 days that we are working in and around Petermann Gletscher.

Wish us luck as we are heading from the green part of Greenland in the south to its white (ice), black (ocean), and gray (land) parts. There are few colors where we will be the next 4 weeks. Our internet will be gone, but I will try to send text files and small photos until we return on 4 September or so, but time will be hard to find. Wish all of us luck …

Preparing for Petermann One Day At a Time

Glaciers, Greenland, Adventure, Expedition, Ice, Polar Bears, Narwhales, oh the fun to go to Greenland.

Swedish icebreaker I/B Oden 22 July 2015 on its way to Thule. [Photo Credit: https://twitter.com/SjoV_isbrytning]

Swedish icebreaker I/B Oden 22 July 2015 on its way to Thule. [Photo Credit: https://twitter.com/SjoV_isbrytning%5D


This romantic notion is false and pretty pictures always lie. To prove my point, I just list what one scientist does 4 days before shipping out to Greenland for 5 weeks. [My wife left last week to visit our grown son in California. She knows the drill, focus, and strain that does not make good company. We have gone through such 4-8 weeks of separation many times during our 20+ years of marriage; her leaving a week before I do works rather well for us]:

04:45 Wake up
05:00 Check e-mail on iPhone in bed
05:05 Read Twitter feed: Canadian research ship diverted to break ice in Hudson Bay
05:10 Check references to outreach-related news
05:15 Read Wilson Quarterly article “The Race to the Arctic” on Arctic developments with global policy impacts
05:30 Shower and Dress
05:45 Check Iridium data collection to Oden, fix minor problem
06:00 Check Hans Island weather, winds still from the north at 10 kts
06:15 Clean up mess cat made, make coffee
06:30 Check latest satellite imagery on Nares Strait, beautiful Arctic lead (upwelling) and sediment plumes from streams and glaciers
07:00 Bicycling to work
07:15 Brief hallway meeting with new grant specialist
07:30 Checking news on Arctic Sea Ice Forums
07:35 Downloading and reading peer-reviewed papers for proposal writing
08:00 Distracted by Tamino’s post about Five signs of denial regarding climate change
08:00 NSF Proposal writing
08:30 Distracted, responding to international e-mails
09:00 Passing links and photos for future press release

My littered office with 2 (of 10) drums of cable to connect ocean sensors through 300 m thick ice to Iridium satellite phone at the surface.

My littered office with 2 (of 10) drums of cable to connect ocean sensors through 300 m thick ice to Iridium satellite phone at the surface.

I am falling behind and feel the tension to get this NSF proposal finished by saturday. NSF stands for National Science Foundation, the proposal is asking for $500,000 to conduct a 3-year experiment with German and Norwegian scientists in the summers of 2016 and 2017. If successful, it will support two graduate students full time for two (MS) and three (PhD) years as well as two technicians for five months total. Peer-review of these proposals is brutal with perhaps a 1:7 success rate on average.

09:15 NSF proposal writing
09:40 Respond to former collaborator on an underwater acoustic communication project
09:45 Back to NSF proposal writing
10:00 Studying Sutherland and Cenedese (2009) on dynamics of the East Greenland Current interacting with canyons as explored by laboratory study
10:30 Converting Latex files to .pdf for uploads to NSF server
11:00 Read and edit UDel Press Release
11:15 Giving university administrators full access to current version of NSF proposal after uploading files to NSF servers
11:20 Heading to coffee shop for short bicycle break
12:00 UNAVCO gear arrived at office
12:05 Re-design the mechanics of the surface mount of the automated weather station to be deployed on Petermann Glacier

UNAVCO GPS systems for deployment on Petermann Gletscher.

12:45 Checking ice and weather in Nares Strait, Arctic Forecast
13:00 Back to proposal, writing/thinking about buoyant coastal currents interacting with canyons
16:00 Meet with PhD student on physics of GPS
16:15 Back to proposal writing
17:30 Graphical layout of proposal
18:15 Bicycle to Main Street for steak + margarita dinner
19:30 Home; set-up overdue MODIS processing
19:45 Edit this list, add links, and photos
19:55 Check Nares Strait weather and DMI Greenland ice
20:15 Daily Iridium data download from Oden works (equipment testing)


20:30 Posting this post
20:45 Editing and updating this post
21:00 Finished processing and posting on my web serverNares Strait MODIS imagery for the week

Petermann Glacier Tidal Heaving

Some glaciers float on the ocean around Antarctica and Greenland. Petermann Gletscher in North Greenland is one of these. It spawned massive Manhattan-sized ice islands in 2010 and 2012. Could tides influence when and where such break-ups occur? After all, the tides under the floating glacier move the ice up and down. But how does a 50 km long, 15 km wide, and 300 m thick floating glacier pivots about its “hinge?” Does it do so like a rigid plate of steel or does it bend and buckle like jelly? I do not know, because nobody has measured the tidal motions of Petermann’s floating ice. So, one of many projects this summer will be to measure tides on Petermann with fancy GPS systems.

Shape of the floating part of Petermann Gletscher (right panel) drom laser altimeters along two tracks flown along the glacier in 2014 (left panel).

Shape of the floating portion of Petermann Gletscher from laser altimeters (right panel) along two tracks flown along the glacier in May of 2014 (left panel).

Martin Jakobsson of Stockholm University posed these questions, sort of, when he asked us American oceanographers, if we had any fancy GPS units to work with one he plans to put high on a cliff overlooking Petermann Fjord. He needs exact positions to map the bottom of the ocean. The cliff-GPS station is fixed while he moves about in a small boat that also has a GPS. Taking the difference of the raw travel times received by the cliff-GPS and the boat-GPS, he can reduce GPS position errors from several meters to several centimeters. People call this differential GPS and he wondered if we oceanographers had any use of it to perhaps give him the tidal corrections he also needs as the measures bottom depths from a boat. Well, this was not initially part of our plan and we did not get funded to study the glacier or the tides under it, but his question got me thinking while Alan Mix of Oregon State University did some organizing. One always squeezes extra science into such great opportunities. Discoveries lurk everywhere to inquiring minds.

Small survey boat loaded onto I/B Oden in Landskrona, Sweden, June 2015.

Small survey boat loaded onto I/B Oden in Landskrona, Sweden, June 2015.

Alan managed to find not one, not two, but three fancy GPS units from an organization that I had never heart of. It is called UNAVCO:

UNAVCO, a non-profit university-governed consortium, facilitates geoscience research and education using geodesy. We challenge ourselves to transform human understanding of the changing Earth by enabling the integration of innovative technologies, open geodetic observations, and research, from pole to pole.

“Geodetic observations” are measurements of locations on the earth’s surface. In the old days surveyors walked about with sextant, clocks, tripods, and optical devices to fix a location and reference it to another. Nowadays satellites and lasers do this faster, but I digress. Suffice it to say, UNAVCO is giving us 3 fancy GPS system to carry with us to Petermann Gletscher to make measurements of tides on the ice. So we can pick 3 locations on the ice where we leave these GPS for the 3-4 weeks next month. I have never done this before, so there will be lots of new learning.

Navigation during early Arctic exploration. Photo taken during a visit of the Peary MacMillan Arctic Museeum at Bowdoin University in Brunswick, Maine.

Navigation during early Arctic exploration. Photo taken during a visit of the Peary MacMillan Arctic Museeum at Bowdoin University in Brunswick, Maine.

I have worked with tides since plunging my head into tidal mud-flats of north-west Germany where I grew up and camping on the shores of the Conwy Estuary in North-Wales where I collected data for my MS thesis. Below I show a 4 week record from three locations in Nares Strait where the tidal elevations range from more than 4 meters at the southern entrance to less than 2 meters in Hall Basin next to Petermann Fjord. The data are from bottom pressure sensors that were deployed for 3-9 years, but I here only want to show the spring-neap cycle. So we already have some idea on how the tides in the ocean next to Petermann Glacier behave.

Sea level fluctuations in meters for 28 days at Discovery Harbor or Fort Conger, Canada near 81.7 N latitude (top), Alexandra Fjord, Canada near 78.9 N latitude (middle), and Foulke Fjord, Greenland near 78.3 N latitude (bottom).

Sea level fluctuations in meters for 28 days at Discovery Harbor or Fort Conger, Canada near 81.7 N latitude (top), Alexandra Fjord, Canada near 78.9 N latiude (middle), and Foulke Fjord, Greenland near 78.3 N latitude (bottom).

Models of tides in Nares Straits do really well if, and only if, the bottom topography is known. And this is where Martin’s mapping of the ocean floor in Petermann Fjord and our tidal observations on the floating glacier come together: We both need good bottom topography, we both use fancy GPS, and we both need to know tides to get accurate bottom depths and we need to know bottom depths to predict tides.

Oceanography of Nares Strait Ice Flushing

I need the ice out of Nares Strait, a 20 mile wide and 300 miles long pathway to the North Pole between northern Canada and Greenland. The ice blocks our way to Petermann Fjord where a large glacier pushes thick ice out so sea as a floating ice shelf. We plan to drill through the floating section of the glacier that is about as thick as the Empire State Building is high. The ship to get us there is the Swedish icebreaker Oden (Location Map). She is passing the Faroe Islands to the north-west of Scotland and will arrive in 2 weeks at Thule Air Force Base where we will meet her.

Image of northern Greenland (top right) and Ellesmere Island (center) showing open water as black, land as gray, and sea ice as gray/white. The two red dots are Thule Air Force Base in the south and Petermann Glacier in the north. Note the bands of black water along the coast of Ellesmere Island that result from east to west blowing winds that move ice offshore.

Image of northern Greenland (top right) and Ellesmere Island (center) showing open water as black, land as gray, and sea ice as gray/white. The two red dots are Thule Air Force Base in the south and Petermann Glacier in the north. Note the bands of black water along the coast of Ellesmere Island that result from east to west blowing winds that move ice offshore and reduce the southward flow in Nares Strait.

The voyage from Thule to Petermann usually takes about 2-3 days, but if the sea ice does not flush out with the generally southward currents, then it may take a week or two wrecking havoc to our busy science schedule. So, why is the ice still lingering in Nares Strait this year?

Nares Strait ice cover in July of 2015 (left), 2014 (center), and 2013 (right) from MODIS Terra.

Nares Strait ice cover in July of 2015 (left), 2014 (center), and 2013 (right) from MODIS Terra.

There are three parts to the answer: First, a sturdy ice arch at the southern entrance of Nares Strait has to break. It has done so only last week. Second, a strong and perhaps oscillating flow has to thoroughly collapse the large pieces of ice at a narrow choke point that is Smith Sound. This has not happened yet. And third, a persistent flow to the south has to flush out ice into Baffin Bay to the south faster than it enters from the Arctic Ocean in the north. This flow is much weaker at the moment than is normal, because winds in the Arctic Ocean have been from east to west right now. These winds moved water (and ice) offshore to the north, so sealevel along northern Greenland and Canada drops. We can see this in today’s satellite imagery as prominent black bands of open water along the coast of northern Canada.

Lets take a closer look of this same image and zoom in on the southern part of Nares Strait as it looked this morning.

Collapsing ice arch at the southern entrance to Nares Strait on 13 July 2015 from MODIS AQUA.

Collapsing ice arch at the southern entrance to Nares Strait on 13 July 2015 from MODIS AQUA.

What used to be a solid frozen mass of ice along the Greenland coast (bottom right) has become a broken and loose mass of smaller ice floes. The larger blocks farther from the coast are now sliding southward as the loose ice along the coast reduces friction or lubricates the edges. The sides lose their grip on the ice and the entire construction fails and collapses. A most beautiful video on the stability of arches is posted by Open University here about lines of action or thrust.

All we now need for the ice to flush out of Nares Strait is a weakening or reversal of the winds at the other northern entrances to Nares Strait. Much of the generally southward flow is caused by the ocean’s surface being higher in the north than it is in the south. There are details that I am skipping, but basically much of the flow rolls downhill like a ball. And with the winds up north being from east to west, there is not much of a hill that the water can flow down, so we got somewhat stagnant waters. I have actually measured the height of this “hill of water” many times over the many years with ocean sensors that measure how much water is above them. This figure summarizes 3 years of data collected every 3 hours or so

Graph showing how water flow (called “volume flux”) varies with the steepness of the hill (called “pressure gradient”). The “hill” is at most 10 centimeters or 3 inches) high. [Adapted from Muenchow, 2015]

Now there is more to the “hill” story that is modified near the surface by the earth’s rotation in a fluid that has different densities at different depths. In a nutshell, the surface flow is 2-3 times as strong as the depth averaged flow. Furthermore, the surface flow on the Canadian side of Nares Strait is often twice as strong as that closer to Greenland, but all these spatial variations in flow actually help to smash large pieces of ice by moving and rotating them different sides of the same large piece of ice differently.

So, lets all hope that we get a few days of strong winds from the north flowing south, that should clear Nares Strait quickly before Oden arrives there in 2 weeks time. Those winds from the north not only flush out ice from Nares Strait, they also keep it nicely on one, the Canadian side. Earth rotation does wonderful and magical things to fluids such as water and air.

Muenchow, A, 2015: Volume and freshwater flux observations from Nares Strait to the west of Greenland at daily time scales from 2003 to 2009. J. Phys. Oceanogr., re-submitted July 2015, .pdf

Coastal Oceanography off North-East Greenland

Greenland is melting, but it is not entire clear why. Yes, air temperatures continue to increase, but what does it matter, if those temperatures are below freezing most of the time. What if the ocean does most of the melting a few 100 m below the surface rather than the air above? It means that gut feeling and everyday experience can be poor guides for science, it means that there is more than meets the eye, and it means that some of Greenland’s melting happens out of sight without the dramatic imagery of a rapidly disintegrating glacier that sends icebergs out to sea.

Floating section of 79N Glacier in north-east Greenland as seen from LandSat in march 2014.

Floating section of 79N Glacier in north-east Greenland as seen from LandSat in march 2014.

In order to “see” where changes may happen out of sight American tax payers supported me via the National Science Foundation (NSF) to use available University of Delaware ocean sensors from an available German ship to investigate the ocean near two large glaciers off north-east Greenland. The sensors are in the water for over a year now and will stay there for another to collect data every half hour. The data are stored on computers inside the sensors and it is a marvel of smart engineering that we can measure water temperature, salinity, and velocity at the bottom of an ice-covered ocean. Now what would I do with such data?

Two ocean sensor packages ready for deployment near Isle de France, Greenland 10 June 2014.

Two ocean sensor packages ready for deployment near Isle de France, Greenland 10 June 2014.

First, one needs to know that in the Arctic Ocean temperature increases as one moves a thermometer from the surface towards the bottom for the first 900 feet or 300 meters. This only make sense, if the warm water is heavier than the cold water above. This is the case in the Arctic, because the warm water at depth is also very salty. The cold waters above contain less salt and that’s why they float. The warmest waters originate from the Atlantic Ocean to the south-east of Iceland. Lets call it Atlantic Water for this reason. The surface waters contain sea ice and its fresh melt water and thus are always close to the freezing point, so lets call them Polar Waters.

Vertical profiles of temperature and salinity across Norske Ore Trough, Greenland. The insert shows station locations for profiles (small symbols) and moorings (large circles). The red dot marks the location of the red profile.

Vertical profiles of temperature and salinity across Norske Ore Trough, Greenland. The insert shows station locations for profiles (small symbols) and moorings (large circles). The red dot marks the location of the red profile.

All along the East Coast of Greenland, we find a strong southward flow of ice and Polar Water called the East Greenland Current. On a rare clear day one can “see” this flow as a beautifully structured undulating band separating the deep Greenland Sea from the shallow and broad continental shelves. Now recall that the warmest waters are in the Atlantic layer way down and somewhat offshore. How do these waters cross the East Greenland current and the very wide continental shelf to reach the glaciers along the coast? It is this question my project tries to answer with lots of help from NSF and German friends.

Satellite image ocean current instabilities on Aug.-19, 2014 as traced by ice along the the shelf break, red lines show 500, 750, and 1000 meter water depth. Small blue triangles top left are ocean moorings.

Satellite image ocean current instabilities on Aug.-19, 2014 as traced by ice along the the shelf break, red lines show 500, 750, and 1000 meter water depth. Small blue triangles top left are ocean moorings.

We think that the warm and salty waters flow near the bottom below the East Greenland Current at deep bottom depressions such as canyons. Testing this idea, we placed our sensors in a line across the canyon with a small ice-capped island called the Isle of France on one side and Belgica Bank on the other. We deployed seven instrument as an array across the canyon to measure the speed and direction of the flow as well as its temperatures and salinities. Our canyon connects the deep Greenland Sea 150 miles to the east with two glaciers another 100 miles to the north-west. We all anxiously hope that no iceberg wiped out bottom moorings and that they all record data faithfully until the summer of 2016 when we plan to recover instruments and data.

Section of temperature across Norske Ore Trough with Isle de France, Greenland on the left and Belgica Bank towards Fram Strait on the right. The view is towards 79N Glacier.

Section of temperature across Norske Ore Trough with Isle de France, Greenland on the left and Belgica Bank towards Fram Strait on the right. The view is towards 79N Glacier.

Before and after the placement of our moored instruments, however, we did survey the section from the ship and I show the temperature and salinity across our canyon. We now see that the water below 200 m depth are indeed very warm and salty as expected, but there is a detail that I cannot yet explain: notice the slight upward sloping contours of salinity near km-80 at the rim of the canyon and the downward sloping contours on the other side near km-10. Such sloping contours represent a flow out of the page at km-80 and into the page at km-10 which is exactly the opposite of what I expected. All I can say at the moment is that this snapshot does not resolve motions caused by the tides, the winds, and the seasonal cycles properly, but our moorings do. So, there are still mysteries to be solved by the data sitting on the bottom of the ocean guarded by towering spectacles of ice.

Tabular iceberg and sea ice cover near Isle de France 10 June 2014

Tabular iceberg and sea ice cover near Isle de France 10 June 2014

[This entry will be submitted to NSF as a Final Outcome Report for award 1362109 “Shelf-Basin Exchange near 79N Glacier and Zachariae Isstrom, North-East Greenland.” The work would not have been possible without the generous support of NSF as well as the German Government as represented by the Alfred Wegener Institute who sponsored the expedition to North-East Greenland in 2014. Torsten Kanzow, Benjamin Rabe, and Ursula Schauer of AWI all deserve as much and even more credit for this work than do I.]

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Hughes, N., Wilkinson, J., & Wadhams, P. (2011). Multi-satellite sensor analysis of fast-ice development in the Norske Øer Ice Barrier, northeast Greenland Annals of Glaciology, 52 (57), 151-160 DOI: 10.3189/172756411795931633

Reeh, N., Thomsen, H., Higgins, A., & Weidick, A. (2001). Sea ice and the stability of north and northeast Greenland floating glaciers Annals of Glaciology, 33 (1), 474-480 DOI: 10.3189/172756401781818554

Wadhams, P., Wilkinson, J., & McPhail, S. (2006). A new view of the underside of Arctic sea ice Geophysical Research Letters, 33 (4) DOI: 10.1029/2005GL025131