Tag Archives: Nares Strait

Ocean Weather Below a Greenland Floating Glacier

Sensing the oceans below ice as thick as the Empire State Building is tall, we are revealing some of the mysteries of ocean melting of one of Greenland’s largest glaciers. The expedition to Petermann Fjord last month made possible the deployment of three ocean sensing stations that all call home daily via Iridium satellite phone to send us new data from 800 meters below sea level. The ice of the glacier at our stations is 100 to 300 meters thick and a whimsical cable with 3 tiny wires connects the instruments under the glacier to a home-made computer that calls home daily with new data. I am still stunned at the many marvels of technology that all came together to make this happen.

University of Delaware PhD student Peter Washam at the Ocean-Weather station on Petermann Gletscher after final installation 2015-Aug.-20, 17:00 UTC at 80 39.9697 N and 60 29.7135 W.

University of Delaware PhD student Peter Washam at the Ocean-Weather station on Petermann Gletscher after final installation 2015-Aug.-20, 17:00 UTC at 80 39.9697 N and 60 29.7135 W.

Panoramic view of the ocean-weather station on Petermann Gletscher. View is towards the south-east with Washington Land in the background.  [Photo credit: Peter Washam].

Panoramic view of the ocean-weather station on Petermann Gletscher. View is towards the south-east with Washington Land in the background. [Photo credit: Peter Washam].

It started with an off-the-shelf automated weather station that David Huntley at the University of Delaware put together for me with the non-standard addition of 5 serial ports that each allow one ocean sensor to be connected by cable to the weather station. It continued with the holes that Paul Anker and Keith Nicholls of the British Antarctic Service drilled through Petermann Gletscher. My PhD student Peter Washam was on the ice helping with the drilling, preparing the ocean sensors, and he is now processing some of the new ocean data.

AWS2015

The map above shows Petermann Gletscher (bottom right), Petermann Fjord, and adjacent Nares Strait. The red lines are bottom depths at 500 and 1000 meters while the thick black line shows the location where the 550-m thick glacier sits on bed rock. All glacier ice seaward of this black line is floating with warm ocean waters below. These waters enter the fjord at he sill at the entrance to Petermann Fjord which is about 450 meters deep. The blue dots are locations where last months we collected detailed profiles of ocean temperature salinity, and oxygen. The warmest water inside the fjord and under the glacier enters near the bottom at this sill. The green dots on the glacier are the 3 drill sites where we put our ocean sensors down while red triangles are “fancy” GPS receivers that we placed for almost 2 weeks on the glacier. The one triangle on land (bottom right) is a permanent GPS station at Kap Schoubye that UNAVCO maintains under the code name SCBY. We will reference our moving glacier GPS station (the glacier moves) to this fixed station on bed rock, but that’s a story for another day.

The ocean data are worked up by a small, but wonder group of men and women of all ages working out of the universities of Gothenburg (Sweden), Oxford (England), and Delaware (USA) as well as BAS (England). It is very much an informal group of people who like each other and met in strange ways over the last year or so with all of us juggling way too many projects for which we all have way too many ideas. Bottom-up collaboration and sharing at its best from the bottom up.

Two quick highlights rushed onto these pages before I have to run off to teach a class on signal processing:

Measurements from the ocean weather station up until 2015-Sept.-11 as a function of time where Day-20 is Aug.-20 and Day-32 is Sept.-1. The station provides battery voltage (bottom panel), air and ocean temperatures, wind speed and direction, ice drift from GPS, and atmospheric pressure (top panel).

Measurements from the ocean weather station up until 2015-Sept.-11 as a function of time where Day-20 is Aug.-20 and Day-32 is Sept.-1. The station provides battery voltage (bottom panel), air and ocean temperatures, wind speed and direction, ice drift from GPS, and atmospheric pressure (top panel).

Ocean temperature (black) and salinity (red) observations from below the ice shelf of Petermann Gletscher at 5 different vertical levels from near the bottom (bottom panel) to the ice-ocean surface (surface panel).

Ocean temperature (black) and salinity (red) observations from below the ice shelf of Petermann Gletscher at 5 different vertical levels from near the bottom (bottom panel) to the ice-ocean surface (surface panel).The bottom of the ice shelf is about 90 meters below sea level.

Note that the scales for temperature and salinity are different at different vertical levels. The warmest water is always found near the bottom while both temperature and salinity under the ice shelf vary by a larger amount that we had initially expected. This means that there are direct and fast connections of the ocean under the glacier with waters inside the fjord and beyond. Notice also that air temperatures are well below freezing (0 degrees Celsius) for 2-3 weeks now while the ocean waters are well above freezing (-1.7 degrees Celsius) everywhere. Hence there is no melting at the surface while there is much melting at the bottom of the glacier. While trivial, this emphasizes the controlling influence that the oceans have on glaciers and ice shelves such as Petermann Gletscher. In the meantime, we got much exciting and fun work ahead of us.

Shout of thanks to NASA (and the US tax-payers) who funded this ocean-weather station at the University of Delaware at about $64,000 for a single year and NSF (and again the US taxpayers) who funded the larger ocean- and land-based experiments within which small part was embedded.

Münchow, A., Padman, L., and Fricker, H.A. (2014). Interannual changes of the floating ice shelf of Petermann Gletscher, North Greenland from 2000 to 2012, Journal of Glaciology, Vol. 60, No. 221, doi: 10.3189/2014JoG13J135

Johnson, H., Münchow, A., Falkner, K., & Melling, H. (2011). Ocean circulation and properties in Petermann Fjord, Greenland Journal of Geophysical Research, 116 (C1) DOI: 10.1029/2010JC006519

Rignot, E., & Steffen, K. (2008). Channelized bottom melting and stability of floating ice shelves Geophysical Research Letters, 35 (2) DOI: 10.1029/2007GL031765

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

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

Sweden’s Icebreaker for Petermann Gletscher 2015

Sweden’s icebreaker I/B Oden will sail for Greenland this summer to pick up about 50 scientists to work the ice, land, water, and glaciers of north-west Greenland with Petermann Gletscher as its focus. I will be working with Celine Heuze of Gothenburg University, Jari Kruetsfeldt of Stockholm Technical University, and Christina, a Swedish High School teacher. Together we are responsible to run the water sampling and ocean sensing.

We met 3 weeks ago on the ship in Landskrona, Sweden where we loaded all our boxes filled with computers, electronics, bottles, rubber hoses, and some more computers. We also met the ship’s crew and a larger group of scientists and engineers from Oregon State University in the US, Gothenburg and Stockholm Universities in Sweden, and the Swedish Polar Research Secretariat that runs the ship. For 3 days we worked, ate, slept (somewhat), and worked some more to get ourselves and our equipment unpacked and organized.

There is nothing romantic about working in an industrial area lugging boxes and stuff up and down stairs from back to front and back again. Despite all the cranes, winches, fork lifts, A-frames, and other tools, it is still back-breaking labor as much is still carried to and fro by hand while watching for heavy loads overhead, sharp corners below, and tight corners to maneuver around. Hard-hats and steel-toed boots are NOT optional. The only positive here is that shared pain brings people together to lower the pain via teamwork.

While most people seem fresh and happy, this wears off after 3 days of intense work not captured in photos. Sleep deprivation sets in as everyone tries to cram too much work into the 24 hours available. And yet, it is during these short and intense work periods, that new friendships and scientific collaborations emerge quickly even though people do not always look their best.

As an example, here is me as a zombie after about 4 nights with little sleep

As always, I try too much as I perform my duties on the water sampling and ocean sensing during the day and fight a nasty Iridium satellite communication problem  at night.  At the University of Delaware we designed, assembled, and shipped off to Sweden an air and ocean weather station to be deployed above and below the floating tongue of Petermann Gletscher. There was no time for testing as all gear to deployed on Petermann Gletscher in August had to be in Landskrona in May.

Despite the looks, I was ecstatic on the inside, because I had just solved a crucial sub-problem when an e-mail reached me that a small NASA grant was coming my way to actually pay for the science that I hope to do during this summer. This, however, is another story for another day.

Sun Set in Nares Strait, Greenland

The sun bathed the southern reaches of Nares Strait in light again after four months of total darkness of the polar night. It is still cold, about -30 degrees centigrade, but the long shadows cast by mountains, hills, and even icebergs from Humbold Glacier are a feast for my eyes:

Kane Basin with Humbold Glacier, Greenland in the east, Ellesmere Island, Canada in the west as well as Smith Sound in the south, and Kennedy Channel of Nares Strait in the north. The visible image was taken Mar.-2, 2015 at 17:30 UTC by MODIS Terra.

Kane Basin with Humbold Glacier, Greenland in the east, Ellesmere Island, Canada in the west as well as Smith Sound in the south, and Kennedy Channel of Nares Strait in the north. The visible image was taken Mar.-2, 2015 at 17:30 UTC by MODIS Terra.

The sun dipped above the southern horizon just for a few hours. The light reflected by the ice and snow of North Greenland was captured by a satellite overhead. From these data I constructed the above image with the axes in km. The frame is big enough to fit both Denmark and Massachusetts into it. The image shows the southern entrance to Nares Strait with its prominent ice arch and the “North Water” polynya in the south. You can “see” individual ice floes in this image as well as rows of sea smoke over the thin ice of the polynya that are all resolved at the 250-m pixel size. Petermann is still dark and not shown, but give it a week, and we’ll get sun there also.

I will be watching this ice arch closely, because together with a group of 50 international scientists I am scheduled to sail these icy waters aboard the Swedish icebreaker Oden this summer for a multitude of experiments to take place in Petermann Fjord with data sampling of adjacent ice, ocean, and land. As a group we will try to reconstruct climate and its physical processes that impact change from tidal to glacial cycles.