Tag Archives: ice shelf

Below Petermann Glacier: The First 100 Days

I am still stunned to see data coming to me hourly from below a glacier in northern Greenland while I sip my breakfast coffee. Each and every day for the last 100 days I got my data fix from the Ocean Weather Station that was born 100 days ago. Every morning at 8:15 the station sends me data from 5 ocean sensors below the glacier. A year ago I did not even know that I would be going to northern Greenland with the Swedish icebreaker I/B Oden in the summer of 2015, never mind that we would be able to pull off the engineering challenge to set up the first and only ocean observing system of Greenland. Today, I am over-joyed to report, we got 100 days of data.

IMG_3029

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.

It all started when a French PhD student approached me at a scientific meeting in San Francisco last December. Céline is a now a doctor of oceanography, but at the time she was not. At the meeting Dr. Céline Heuzé of the University of Gothenburg in Sweden asked me for data and insights on how the ocean circulation in Nares Strait worked, so that she could connect results from planned field work in northern Greenland to her science interests in the Labrador Sea more than 1000 miles to the south. She also introduced me to Dr. Anna Wåhlin and the three of us got very excited about Petermann Fjord, Sweden, and polar oceanography. Here we are in Sweden preparing and off Greenland working:

A few weeks prior the US government and Sweden had just agreed to work together on a joint expedition to Petermann Fjord in northern Greenland. Friends at Oregon State University needed a ship to collect data with which to reconstruct and understand changes of the land- sea-, and ice-scape of North Greenland during the last 10,000 to 50,000 years. They wanted to uncover where past glaciers were located and where sea level was at that time. For this, they needed many sediment cores from the adjacent ocean, fjord, and below the floating glacier. Today this glacier is as thick as the Empire State Building in Manhattan is high. The British Antarctic Survey (BAS) agreed to drill the holes, collect the sediment samples, and take a profile of ocean properties from below the glacier ice to the bottom of the ocean. They estimated it would take about 5 days to drill each hole. Our idea was to use these holes to keep sensors, computers, and satellite phones in place to collect hourly data into the future as long as possible … 100 days so far.

After the Dec.-2014 San Francisco meeting we decided to use these holes to measure ocean temperature, salinity, and pressure for as long as the batteries would last, about 3-4 years, but I had neither money, cables, data logging computers, nor satellite phones to do any of this, only the ocean sensors. When I told Keith Nicholls of BAS about the idea and my predicament, he said that he could find some computers and satellite phones from experiments he had done in Antarctica. I then said that I would organize cables, a weather station, and some funds to pay for it.

A crowd-funding experiment in February failed to generate funds, but NASA came to the rescue by opening a way to compete for the needed $60,000 to cover the cost of hardware, travel, and satellite phone charges. The funds allowed us to ship about 1200 pounds of gear from Delaware to Sweden where it had to be loaded onto the ship in May of 2015. We did not have much time to built the system and had no time left to test it. Two drums of cable arrived with only 5 hours to spare before the ship left Sweden in June for Greenland. We met the ship in Thule, Greenland in July.

Fast-forward to the 20th of August 2015 when our ocean observing system went into the salty ocean waters below Petermann Gletscher. The surface weather station with satellite connections was deployed 10 days earlier to test satellite communications and collect weather data for Oden’s extensive helicopter flight operations on and around the glacier. It included a rushed visit by a large team from CBS News 60 Minutes who were flown and shown all over the place. We last saw the station during 24 hours of day light on 27th August when we calibrated the wind sensors, but to me the daily satellite phone call of the station with new data is a sign of life from an ocean outpost that survived another day in the total darkness of the polar night. It draws energy from two car batteries that run even at the -36 degree Centigrade (-33 F).

AWS

First 100 days of ocean and weather observations from the University of Delaware Ocean Weather Station on Petermann Gletscher, Greenland. Panels show (from bottom to top) time series of 1. battery voltage, 2. ocean (red) and air (black) temperatures, 3. wind speed, 4. wind direction, 5. glacier movement, and 6. atmospheric pressure. Time is given in year-day, Nov.-28 is Day-332. The sun set on Day-290 or Oct.-17.

New data are posted at

http://ows.udel.edu

which over the next few weeks we will develop into a web-site to distribute the daily observations to everyone. I am most thankful to many of scientists, engineers, technicians, sailors, and women in England, Sweden, and the United States of America, but this Thanks-Giving weekend I am grateful to the men and women of a great nation that gave me a place to study, work, and live doing while exploring ocean and now glacier physics as well.

EDIT: I just discovered this 7 minute video on our expedition, credits go to Saskia Madlener at 77th Parallel Productions:

Petermann Glacier Shape and Melt Channels

Radars, lasers, and fancy computers all shape the way we see the shape of glaciers. An airplane flies along a line down the glacier with (1) a good GPS. It carries (2) a vertical laser that measures the distance from the plane to the surface below while (3) an ice-penetrating radar measures where the ice meets the ocean. All these data are distributed freely by the University of Kansas’ Center for Remote Sensing of Ice Sheets (CReSIS) that is part of NASA’s Operation IceBridge.

March-24, 2010 view of Petermann Glacier from NASA’s DC-8 aircraft. Photo credit goes to Michael Studinger of NASA’s IceBridge program who also blogged about this flight.

From CReSIS I gathered the data from Petermann Glacier before its break-up in 2010 and 2012. I show two flight tracks on a MODIS map for the same day that NASA’s DC-8 was collecting the shape data. There are two tracks as the airplane flies along the fjord out towards the ocean, turns, and flies back up inland. The seaward (red) track is slightly offset from the landward (black) track.

Petermann Glacier on March 24, 2010 from MODIS. The left panel shows the reflectance while the right panel shows the magnitude of the spatial gradient of this signal. Red and black dots are the flight tracks from which the shape of the glacier was measured by radar flown on a DC-8. The dark black line indicates where the glacier is grounded to bed rock ~500 meters below sea-level. The 3 boxes indicate location where the floating ice shelf terminated before 2010 (top box), after 2010 (middle box), and now (bottom box) due to the 2010 and 2012 ice islands. Top left are clouds, mountain shadows on left also.

The laser gives us the top surface of the ice while the radar gives us the bottom surface. Connect these two and we get ice thickness. Below I show how these ice elevations change along the glacier. The ocean is to the right near 65 km while the grounding line of the glacier is near -20 km, so the part of the glacier that is floating on the ocean was about 80 km in 2010, that’s about 50 miles. Now why is the red shape so different from the black line?

Shape of Petermann Glacier’s floating ice shelf on March 24, 2010 (top panel) and ice thickness (bottom panel). Radar data from University of Kansas, Center for Remote Sensing of Ice Sheets (CReSIS) with EGM2008 geoid corrections applied by me.

Well, the two tracks were NOT the same and these data show that the glacier varies in thickness and shape at small scales. The floating ice-sheet has lots of topography. It has hills, valleys, channels, and troughs. It stuns me to see how long and how steep this one specific channel is: it changes by almost 200 meters in 2 km. That’s huge. We do not fully understand how these channels form, why they are there, if they change over time, or perhaps most importantly, how do they relate to the stability of this or other glaciers. A first theoreticial PhD thesis was recently submitted by Carl Gladish. It is thought-provoking, but it does not settle the issue. We do not even know how many such channels there are, but there are ideas on how to perhaps do this with data both in hand and more to be collected.

Simplifying future analyses, I changed my Petermann MODIS and CReSIS co-ordinate system from latitude and longitude to a distance in kilometers along and across the glacier. The standard MODIS “color” (lets call this f) varies as one walks the glacier in its along-stream (call this x) and across-stream (call this y) directions. The color f is a function of x and y which scientists write as f=f(x,y). Now compare this color f(x,y) with the SPATIAL CHANGE (call this the slopes) of color that I show in the right panel. The MODIS data are the same, but why do they look so different in the two panels?

Well, the slopes draw the eye to smaller scale features in the right panel. This technique sharpens edges, fronts, and small spatial irregularities that our eyes tend to skip over. Our brains are trained to integrate and to condense information looking for the largest patterns first. So, taking the difference between adjacent values to get slopes and shapes, I do exactly the opposite and make sure that small irregularities stand out:

Close-up of March 24, 2010 MODIS image from the grounding line (black line at bottom) to the location of the present seaward front of the glacier (black box at top).

Notice the many stripes along the glacier near the bottom (x=0) right (y=80) near where the red triangle is. I believe these structures relate to sub-surface melt-channels of intense ice-ocean interactions, but belief is not truth and as scientists we must proof our believes and truths in ways that other people can check by repeating the experiments or calculations. There is so much more fun work to do, but, sadly, there are only 24 hours to a day.

Oh, and a (British) submarine is perhaps on the way to dive under this ice-shelf to take a close look and lots of data of under-ice topography, temperature, salinity, and bottom topography, if we can get a ship and experiment to get it there. So much work to do … [to be continued]