Tag Archives: iridium

Greenland Oceanography by Sled and Snowmobile

Wind chill matters in Greenland because one must see and breath. This implies exposed skin that will hurt and sting at first. Ignoring this sting for a few minutes, I notice that the pain goes away, because the flesh has frozen which kills nerves and skin tissue. The problem becomes worse as one drives by snowmobile to work on the sea ice which I do these days almost every day.

Navigating on the sea ice by identifying ice bergs with LandSat imagery. The imagery also shows polynyas and thin ice in the area. [Photo Credit: Sonny Jacobsen]

Mar.-22, 2017 LandSat image of study area with Thule Air Base near bottom right, Saunders Island in the center. Large red dots are stations A, B, and C with Camp-B containing weather station, shelter, and first ocean mooring. My PhD student Pat Ryan prepared this at the University of Delaware.

My companion on the ice is Sonny Jacobsen who knows and reads the land, ice, and everything living on and below it. He teaches me how to drive the snowmobile, how to watch for tracks in the snow, how to pack a sled, and demonstrates ingenuity to apply tools and materials on-hand to fix a problem good enough to get home and devise a new and better way to get a challenging task done. Here he is designing and rigging what is to become our “Research Sled” R/S Peter Freuchen, but I am a little ahead of my story:

Sonny Jacobsen on Mar.-27, 2017 on Thule Air Base building a self-contained sled for ocean profiling.

First we set up a shelter in the center of what will hopefully soon become an array of ocean sensors and acoustic modems to move data wirelessly through the water from point A in the north-west via point B to point C. Point C will become the pier at Thule Air Base while the tent is at B that I call Camp-B:

Ice Fishing shelter to the north-east of Saunders Island seen to the left in the background.

Next, we set up an automated weather station (AWS) next to this site, because winds and temperatures on land next to hills, glaciers, and ice sheets are not always the same 10 or 20 km offshore in the fjord. It is a risk-mitigating safety factor to know the weather in the study area BEFORE driving there for 30-60 minutes to spend the day out on the ice. It does not hurt, that this AWS is also collecting most useful scientific data, but again, I am slightly ahead of my story:

Weather station with shelter at Camp-B with the northern shores of Wolstenholme Fjord in the background. Iridium antenna appears just above the iceberg on the sidebar of the station. Winds are measured at 3.2 m above the ground.

With shelter and weather station established and working well, we decided to drill a 10” hole through 0.6 m thin ice to deploy a string of ocean instruments from just below the ice bottom to the sea floor 110 m below. Preparing for this all friday (Mar.-24), we deploy 22 sensors on a kevlar line of which 20 record internally and must be recovered while 2 connect via cables to the weather station to report ocean temperature and salinity along with winds and air temperatures. It feels a little like building with pieces of Lego as I did as a kid. Engineers and scientists, perhaps, are trained early in this sort of thing.

Weather station with ocean mooring (bottom right) attached with eastern Saunders Island in the background on Sunday Mar.-26, 2017.

Sadly, only the ocean sensor at the surface works while the one at the bottom does not talk to me. I can only suspect that I bend a pin on the connector trying to connect very stiff rubber sealing copper pins from the cable with terminations equally stiff in the cold, however, there are other ways to get at the bottom properties albeit with a lot more effort … which brings me to R/S Peter Freuchen shown here during its maiden voyage yesterday:

R/S Peter Freuchen in front of 10” hole (bottom right) for deployment of a profiling ocean sensor. The long pipes looking like an A-frame on a ship become a tripod centered over the hole with the electrical winch to drive rope and with sensors (not shown) over a block into the ocean. This was yesterday Mar.-28, 2017 on the way from Camp-B back to Thule Air Base.

The trial of this research sled was successful, however, as all good trials, it revealed several weaknesses and unanticipated problems that all have solutions that we will make today and tomorrow. The design has to be simple to be workable in -25 C with some wind and we will strip away layers of complexities that are “nice to have” but not essential such as a line counter and the speed at which the line goes into the water. There can not be too many cables or lines or attachments, because any exposure to the elements becomes hard labor. This becomes challenging with any gear leaving the ocean (rope, sensors) and splattering water on other components. Recall that ocean water is VERY hot at -1.7 C relative to -25 C air temperatures. This means that ANYTHING from the ocean will freezes instantly when in contact with air. Efficiency and economy matter … as does body heat to keep critical sensors and batteries warm.

A big Thank-You to Operation IceBridge’s John Woods for something related to this post that I wish not to advertise 😉

Oceanography below Petermann Gletscher for 400 Days

Ocean data from 810 meters below sea level under one of Greenland’s last remaining ice shelves arrives every 3 hours at my laptop via a 3-conductor copper cable that passes through 100 meter thick ice to connect to a weather station that via a satellite phone system connects to the rest of the world. This Ocean-Weather station on the floating section of Petermann Gletscher has reported for 400 days today. I am still amazed, stunned, and in awe that this works.

The station started 20th August of 2015 as a small part of a larger joint US-Swedish expedition to North Greenland after friends at the British Antarctic Survey drilled holes through the Empire-State-Building thick ice shelf. It is powered by two 12 Volt car batteries that are recharged by two solar panels. When the sun is down, the car batteries run the station as in winter when temperatures reached -46 C. When the sun is up, the solar cells run the station and top off the batteries. The voltage during the last 400 days shows the “health” of the station:

Battery voltage at the Petermann Ocean-Weather Station from Aug.-20, 2015 through  Sept.-23, 2016. The polar night is indicated by slowly declining voltage near 12 V while during the polar day voltage is near 14 V with oscillations in spring and fall during the transition from 24 hours of darkness to 24 hours of sun light.

Battery voltage at the Petermann Ocean-Weather Station from Aug.-20, 2015 through Sept.-23, 2016. The polar night is indicated by slowly declining voltage near 12 V while during the polar day voltage is near 14 V with oscillations in spring and fall during the transition from 24 hours of darkness to 24 hours of sun light.

There is an unexplained outage without data from February 12-25 (Day 175-189) which happened a day after the first data logger shut down completely without ever recovering. Our station has 2 data loggers: A primary unit controls 2 ocean sensors, atmospheric sensors, and the Iridium satellite communication. The secondary unit controls 3 ocean sensors and the GPS that records the moving glacier. Remote access to the secondary logger is via the primary, however, each logger has its own processors, computer code, and back-up memory card.

Inside of University of Delaware command and control of five ocean sensors and surface weather station. Two data loggers are stacked above each other on the left.

Inside of University of Delaware command and control of five ocean sensors and surface weather station. Two data loggers are stacked above each other on the left.

The primary logger failed 11th February 2016 when we received our last data via Iridium satellites until Keith Nicholls and I visited the station 27th and 28th August 2016 via helicopter from Thule, Greenland. Since I could not figure out what went wrong sitting on the ice with the helicopter waiting, I spent a long night without sleep to swap the data logger with a new and tested unit. I rewired sensors to new data logger, switched the Iridium modem, transceiver, and antenna, changed the two car batteries, and now both data loggers with all five ocean sensors have since reported faithfully every 3 hours as scheduled as seen at

http://ows.udel.edu

Lets hope that the station will keep going like as it does now.

The major discovery we made with the ocean data are large and pronounced pulses of fresher and colder melt waters that swosh past our sensors about 5 and 25 meters under the glacier ice. These pulses arrive about every 14 days and this time period provides a clue on what may cause them – tides. A first descriptive report will appear in December in the peer-reviewed journal Oceanography. Our deeper sensors also record increasingly warmer waters, that is, we now see warm (and salty) waters under the glacier that in 2015 we saw more than 100 km to the west in Nares Strait. This suggests that the ocean under the glacier is strongly coupled to the ambient ocean outside the fjord and vice versa. More on this in a separate future posting.

Time series of salinity (top) and potential temperature (bottom) from four ocean sensors deployed under the ice shelf of Petermann Gletscher from 20th of August 2015 through 11th of February 2016. Temperature and salinity scales are inverted to emphasize the vertical arrangements of sensors deployed at 95m (black), 115 (red), 300 m, and 450 m (blue) below sea level. Note the large fortnightly oscillations under the ice shelf at 95 and 115 m depth in the first half of the record. [From Muenchow et al., 2016]

Time series of salinity (top) and potential temperature (bottom) from four ocean sensors deployed under the ice shelf of Petermann Gletscher from 20th of August 2015 through 11th of February 2016. Temperature and salinity scales are inverted in order to emphasize the vertical arrangements of sensors deployed at 95m (black), 115 (red), 300 m, and 450 m (blue) below sea level. Note the large fortnightly oscillations under the ice shelf at 95 and 115 m depth in the first half of the record. [From Muenchow et al., 2016]

P.S.: The installation and year-1 analyses were supported by a grants from NASA and the Jet Propulsion Laboratory, respectively, while the current work is supported by NSF for the next 3 years. Views and opinions are mine and do not reflect those of the funding agencies.

Greenland Calling: Iridium Satellite Phone

I have trouble calling Petermann Gletscher, Greenland where I am collecting ocean data that feeds into a remote weather station. This station is run on a pair of car batteries, because the solar panels do not work until the sun rises again in two months and the next electrical outlet is about 300 miles away. A computer controls power to sensors and a satellite phone. All calls from and to the station are routed via a commercial satellite phone system that consists of about 66 satellites orbiting our planet. They often appear as shooting stars in the night sky that are called Iridium flares. As beautiful as these orbiting satellites are, they have driven me mad.

Screen shot of Iridium satellite orbits observed in real-time from http://www.satflare.com/track.asp?q=iridium

Screen shot of Iridium satellite orbits observed in real-time from http://www.satflare.com/track.asp?q=iridium

Iridium satellite phones and modems connected to computers are the only way to get data from remote areas of the Arctic and Antarctic. Some modems send small text messages called Short-Burst-Data (SBD) while other modems support a true two-way dial-up connection that includes all the hand-shaking of a telephone call. This computer-to-computer calling is more tricky than the person-to-person calls that this system was originally designed for. Working near Petermann Fjord, we had much trouble with even the person-to-person calls. Senator John McCain’s of the U.S. Congress was rudely disconnected, when he called us on the ship while in Sweden working with Government officials. And the Iridium phones on our Swedish icebreaker I/B Oden were thoroughly checked by field technician Robert Holden:

Rob Holden testing Iridium phones above the bridge of I/B Oden.

Robert Holden testing Iridium phones above the bridge of I/B Oden in August of 2015.

The building and coding of this ocean weather station is cool stuff for someone like me who likes Legos, computer games, and hacking electronics. Our Greenland ocean observing system uses both the text message SBD system at two smaller stations and the dial-up system at the larger weather station. The SBD system is great for small burst of data smaller than 1960 bytes per message. The Greenland station makes the call to a ground station that then e-mails the message forward to us. The method is very reliable, but there are small connection gaps that become data gaps.

Inside of University of Delaware command and control of five ocean sensors and surface weather station. Two computers are stacked above each other on the left.

Inside of University of Delaware command and control of five ocean sensors and surface weather station. Two computers are stacked above each other on the left with satellite modem 9522B on bottom left with RS-232 cable connecting to computer (Campbell Scientific CR1000).

In contrast, the dial-up method delivers a gap-free data set, but its bi-polar behavior drives me nuts. There are periods when each scheduled call results in a connection and new data, but there are also periods when each scheduled call fails to connect. Over the last 4 months I made 1450 calls to Greenland. Only 189 of these 1450 calls resulted in a connection. That is a failure rate of 87%. It admittedly includes one desperate day (Sept.-18) when I made a call every 3 minutes and each call failed. This desperation was after a 10-day sequence of failed calls when I lost my cool. There were 86 out of 130 days when a successful connection was made, that’s still a large failure rate of 34%, but there are zero missing data so far. [The station was set up Aug.-20.]

Logs-OWS

The advantage of the fickle dial-up connection is that I only need one connection to recover all data that has been collected since the last successful call. This differs from the SBD text message, where a lost connection means lost data. Furthermore, the connection to the Greenland station is a regular RS-232 connection which acts the same as the iPhone connected to the computer from which I type these lines. Hence software changes are possible, too, as scary as they may be.

Now why is the Iridium connection acting in a such a bi-polar fashion, that is, working like a charm for weeks and months to suddenly shut down completely for days to weeks just as suddenly? My honest answer is that I do not know. Furthermore, nobody really knows for sure. There is some talk in hidden places that Iridium modems or phones “de-register” themselves from the Iridium network, if they do not start a phone call. This is no problem for the SBD message as the Greenland modem always does the calling. It does matter for my dial-up, because the Greenland modem never initiates a call, it only responds when called after the Greenland computer gives it the power to do so. Which brings me to

‘Fake call’
Register_Modem = “ATDT 1234″ & CHR(13) & CHR(10)
SerialOpen (ComRS232,19200,0,0,2000)
Delay (0,1,Sec)
SerialOut (ComRS232,Register_Modem,””,0,0)
SerialClose (ComRS232)

The “fake call” is a software update that tells the Greenland modem to, well, make a fake call. The text string Register_Modem contains a non-existing phone number (I hope) 1234 as well as a carriage return CHR(13) and a line feed CHR(10) and the string is send via SerialOut to the modem that is addressed here as ComRS232 after the serial port between Greenland computer and modem is opened via SerialOpen. Lets see how this works over the next days, weeks, and months. For the first time, I received this morning a response from Greenland that it was “BUSY.” I took this as a good sign …

PostScript: Data look awesome with new, large, and unexpected diurnal variations that started Dec.-8.

Ocean temperature (black) and salinity (red) below Petermann Gletscher from Dec.-6 (Day-340) through Dec.-31 (Day-365). Top panel is just below the glacier ice at 95-m below sea level while bottom panel shows data 810-m below sea level.

Ocean temperature (black) and salinity (red) below Petermann Gletscher from Dec.-6 (Day-340) through Dec.-31 (Day-365). Top panel is just below the glacier ice at 95-m below sea level while bottom panel shows data 810-m below sea level.

New ocean data from floating Petermann Glacier

#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.

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