Robots in the Antarctic study 'rapidly melting ice'

Robotic Ocean Gliders Aid Study of Melting Polar Ice

Caltech Seaglider being released into the Weddell Sea off the coast of the Antarctic Peninsula in January 2012. The glider would be left to sample the region for about two months, measuring temperature, salinity and ocean currents to better understand how the ocean contribute to heat transport towards the Antarctic coastline. Credit: Andrew Thompson/Caltech - See more at: http://www.caltech.edu/content/robotic-ocean-gliders-aid-study-melting-polar-ice#sthash.H7ad95LZ.dpuf

Caltech Seaglider being released into the Weddell Sea off the coast of the Antarctic Peninsula in January 2012. The glider would be left to sample the region for about two months, measuring temperature, salinity and ocean currents to better understand how the ocean contribute to heat transport towards the Antarctic coastline. Credit: Andrew Thompson/Caltech

The rapidly melting ice sheets on the coast of West Antarctica are a potential major contributor to rising ocean levels worldwide. Although warm water near the coast is thought to be the main factor causing the ice to melt, the process by which this water ends up near the cold continent is not well understood.

Using robotic ocean gliders, Caltech researchers have now found that swirling ocean eddies, similar to atmospheric storms, play an important role in transporting these warm waters to the Antarctic coast—a discovery that will help the scientific community determine how rapidly the ice is melting and, as a result, how quickly ocean levels will rise.

Their findings were published online on November 10 in the journal Nature Geoscience.

“When you have a melting slab of ice, it can either melt from above because the atmosphere is getting warmer or it can melt from below because the ocean is warm,” explains lead author Andrew Thompson, assistant professor of environmental science and engineering. “All of our evidence points to ocean warming as the most important factor affecting these ice shelves, so we wanted to understand the physics of how the heat gets there.”

Ordinarily when oceanographers like Thompson want to investigate such questions, they use ships to lower instruments through the water or they collect ocean temperature data from above with satellites. These techniques are problematic in the Southern Ocean. “Observationally, it’s a very hard place to get to with ships. Also, the warm water is not at the surface, making satellite observations ineffective,” he says.

Because the gliders are small—only about six feet long—and are very energy efficient, they can sample the ocean for much longer periods than large ships can. When the glider surfaces every few hours, it “calls” the researchers via a mobile phone–like device located on the tail. This communication allows the researchers to almost immediately access the information the glider has collected.

Like airborne gliders, the bullet-shaped ocean gliders have no propeller; instead they use batteries to power a pump that changes the glider’s buoyancy. When the pump pushes fluid into a compartment inside the glider, the glider becomes denser than seawater and less buoyant, thus causing it to sink. If the fluid is pumped instead into a bladder on the outside of the glider, the glider becomes less dense than seawater—and therefore more buoyant—ultimately rising to the surface. Like airborne gliders, wings convert this vertical lift into horizontal motion.

Thompson and his colleagues from the University of East Anglia dropped their gliders into the ocean off the coast of the Antarctic Peninsula in January 2012; the robotic vehicles then spent the next two months moving up and down through the water column—diving a kilometer below the surface of the water and back up again every few hours—exploring the Weddell Sea off the coast of Antarctica. As the gliders traveled, they collected temperature and salinity data at different locations and depths of the sea.

The glider’s up and down capability is important for studying ocean stratification, or how water characteristics, such as density, change with depth, Thompson says. “If it was only temperature that determined density, you’d always have warm water at the top and cold water at the bottom. But in the ocean you also have to factor in salinity; the higher the salinity is in the water, the more dense that water is and the more likely it is to sink to the bottom,” he says.

In Antarctica the combined effects of temperature and salinity create an interesting situation, in which the warmest water is not on top, but actually sandwiched in the middle layers of the water column. “That’s an additional problem in understanding the heat transport in this region,” he adds. You can’t just take measurements at the surface, he says. “You actually need to be taking a look at that very warm temperature layer, which happens to sit in the middle of the water column. That’s the layer that is actually moving toward the ice shelf.”

The results from the gliders revealed that the heat was actually coming from a less predictable source: eddies, swirling underwater storms that are caused by ocean currents.

“Eddies are instabilities that are caused by ocean currents, and we often compare their effect on the ocean to putting a spoon in your coffee,” Thompson says. “If you pour milk in your coffee and then you stir it with a spoon, the spoon enhances your ability to mix the milk into the coffee and that is what these eddies do. They are very good at mixing heat and other properties.”

Because the gliders could dive and surface every few hours and remain at sea for months, they were able to see these eddies in action—something that ships and satellites had previously been unable to capture.

“Ocean currents are variable, and so if you go just one time, what you measure might not be what the current looks like a day later. It’s sort of like the weather—you know it’s going to be warm in the summer and cold in the winter, but on a day-to-day basis it could be cold in the summer just because a storm came in,” Thompson says. “Eddies do the same thing in the ocean, so unless you understand how the temperature of currents is changing from day to day—information we can actually collect with the gliders—then you can’t understand what the long-term heat transport is.”

In future work, Thompson plans to couple meteorological data with the data collected from his gliders. In December, the team will use ocean gliders to study a rough patch of ocean between the southern tip of South America and Antarctica, called the Drake Passage, as a surface robot, called a Waveglider, collects information from the surface of the water. “With the Waveglider, we can measure not just the ocean properties, but atmospheric properties as well, such as wind speed and wind direction. So we’ll get to actually see what’s happening at the air-sea interface.”

In the Drake Passage, deep waters from the Southern Ocean are “ventilated”—or emerge at the surface—a phenomenon specific to this region of the ocean. That makes the location important for understanding the exchange of carbon dioxide between the atmosphere and the ocean. “The Southern Ocean is the window through which deep waters can actually come up to ‘see’ the atmosphere”—and it’s also a window for oceanographers to more easily see the deep ocean, he says. “It’s a very special place for many reasons.”

The work with ocean gliders was published in a paper titled “Eddy transport as a key component of the Antarctic overturning circulation.” Other authors on the paper include Karen J. Heywood of the University of East Anglia, Sunke Schmidtko of GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany, and Andrew Stewart, a former postdoctoral scholar at Caltech who is now at UCLA. Thompson’s glider work was supported by an award from the National Science Foundation and the UK’s Natural Environment Research Council; Stewart was supported by the President’s and Director’s Fund program at Caltech.

Written by Jessica Stoller-Conrad

==========================================

antarctic_seaice_sept19[1]

Advertisements

76 thoughts on “Robots in the Antarctic study 'rapidly melting ice'

  1. “””””…..The rapidly melting ice sheets on the coast of West Antarctica are a potential major contributor to rising ocean levels worldwide. Although warm water near the coast is thought to be the main factor causing the ice to melt, the process by which this water ends up near the cold continent is not well understood……”””””
    Um Sir, doesn’t the water jut slosh up against the land ?? I Think that is how the cast is defined !

  2. “When the glider surfaces every few hours, it “calls” the researchers via a mobile phone..”

    Hmmm… So what does it do if it can’t surface because the sea is covered in ice? Or do they just go to places that are ice-free?

  3. Boys and their toys – what fun it is to take our toys, expenses and salaries to sea at the taxpayers expense…

  4. BS.
    “Rapidly melting Antarctic sea ice” at the same time as Antarctic sea-ice record extent.
    Who peer-reviewed this cr*p??
    BTW, “melting ice sheets” do not contribute to sea-level change because ice sheets float.

    • BTW, “melting ice sheets” do not contribute to sea-level change because ice sheets float.

      Ice sheets do contribute to sea level rise. Ice sheets cover land which also means your first statement about Antarctic sea ice is irrelevant.

    • Re-read the title, it doesn’t say “rapidly melting SEA ice.” The article of course is talking about land ice.

      • So, the water in those warm currents lapping against the coast are enough to warm the land under the ice. How warm are these currents, again??

      • Right. It is only the subtitle Robotic Ocean Gliders Aid Study of Melting Polar Ice. Not a sea ice 🙂

      • Barry
        November 12, 2014 at 2:51 pm
        Re-read the title, it doesn’t say “rapidly melting SEA ice.” The article of course is talking about land ice.

        Are you sure Barry? Here is a part of the article.

        “When you have a melting slab of ice, it can either melt from above because the atmosphere is getting warmer or it can melt from below because the ocean is warm,” …….“All of our evidence points to ocean warming as the most important factor affecting these ice shelves, so we wanted to understand the physics of how the heat gets there.”

      • “””””…..Although warm water near the coast is thought to be the main factor causing the ice to melt, the process by which this water ends up near the cold continent is not well understood….”””””
        So Barry, what is so hard to understand about warm water near the coast sloshing up on top of those land ice sheets, and melting it. Do you have any references to such a phenomena being observed ??
        And why would they try to observe land ice melting using a diving gizmo that is out in the sea, not under the land ice ??

    • The entire article is about sea ice melting due to warm water.
      Water / seawater is mentioned 21 times
      Land is mentioned zero

      • Where do folks get the LAND ice from this article? I read it and am baffled. They even show us their “Seaglider” being released into the “Weddell Sea off the coast of the Antarctic Peninsula” to measure “salinity and ocean currents” and so on.
        Now please don’t make me bring up volcanoes and geothermals.

      • jimbo i have read several articles on glaciers melting due to warmer waters and it has been cfazily confusing at first read when the authors say melt is due to warmer water reaching the grounding point. The “warmer water” happens locally when the upwelled deep water reaches the grounding point more directly. The longer it takes to traverse the coastal shelves, the more it cools locally.The circumpolar deep water’s temperature changes very slowly on centennial and millennial time scales. But often published articles do not make that distinction clear or worse a few imply the deep water has warmed due to climate change.

    • An ice shelf is a thick floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Sea ice is also formed on the ocean but is much thinner.

  5. Any GCM would also have to model the planet’s water, all the currents, tides, winds, temps…a rather impossible thing to do.

  6. so they started this “survey” when Antarctic ice was retreating…and by the time they finally got it out to publish…..everything was going the other way
    I just love it……….proof, they don’t know squat

  7. “When you have a melting slab of ice, it can either melt from above because the atmosphere is getting warmer or it can melt from below because the ocean is warm,” … or perhaps there may be a humungous ooze of magma related to the active volcanoes in West Antarctica which is giving some high heat flow and causing some ice to melt!!

  8. Since when did melting sea ice have any measurable effect on sea levels? Sounds like “rising sea level” was added to attract green grant $$$. Gliders are not new. The Integrated Ocean Observing System (IOOS®) has been using them for years to map ocean currents, temperature, etc.

  9. “When you have a melting slab of ice, it can either melt from above because the atmosphere is getting warmer or it can melt from below because the ocean is warm,” explains lead author Andrew Thompson, assistant professor of environmental science and engineering. “All of our evidence points to ocean warming as the most important factor affecting these ice shelves
    There are no measurements (evidence) of the relative importance of surface and bottom melt in ice sheet retreat (‘melt’).
    No one disputes ocean upwelling and ocean currents around Antarctica cause ice sheet melt, the issue is whether changes in these factors have caused an increase in icesheet melt.
    Saying “All of our evidence points to ocean warming as the most important factor affecting these ice shelves” is little more than ideology.

  10. “The rapidly melting ice sheets on the coast of West Antarctica are a potential major contributor to rising ocean levels.” All climatologists are same. A 2.5% error in a latent heat of water vaporization in CAM5 model is “a potential problem.”

  11. Strange this has to happen in the one part of Antarctica well known for its geothermal activity.
    Did this not occur to these jokers, or did they deliberately choose to ignore it? Either way, it smacks of incompetence.
    Just one of those inconvenient facts that tends to rubbish so much of classic alarmist theory.

  12. In the polar regions the warmer water is found 100 meters below the surface. Where glaciers have grounding points in deeper waters where relatively upwelled water can reach their grounding points, those glaciers have been melting and unstable, contributing to almost all of Antarctica’s loss ice mass. Nearby glaciers with grounding points not accessible to those upwelled waters have not shrunk.
    Basal melting is limited to a very few places, with the Amundsen Sea being the hot spot. Basal melting has been inferred fo nearly a century due to the concave shapes of those glaciers. The process of basal melting has likely been going on since the end of the last Age as 1) sea level rose bring warm deep waters closer to the grounding points and 2) once the grounding point retreated from the edge of the shallow coastal shelves, upwelled water can flow into a cavity causing the grounding point to recede further creating a positive feedback that will not reverse until the next ice age.
    http://cdn.antarcticglaciers.org/wp-content/uploads/2014/05/PIG.ai_-1024×586.jpg

    • I always want to put a caption on that diagram between ‘Circumpolar deep water’ and ‘continental shelf’ that says ‘Continental overhang’.

    • Jim, while this is the conventional view, observations tend to not support this.
      E.g. This study that concludes,
      ‘Previous studies and morphologic mapping of the fjord suggest that the Crane Glacier grounding zone was well within the fjord before 2002 and did not retreat further until after the ice shelf collapse. This implies that the 2002 Larsen-B Ice Shelf collapse likely was a response to surface warming rather than to grounding zone instability, strengthening the idea that surface processes controlled the disintegration of the Larsen Ice Shelf.
      http://www.sciencemag.org/content/345/6202/1354.abstract

      • Philip I am not sure why you suggest what I have said would be at odds with Rebesco paper and Larsen B collapse. The paper merely argues that the Larsen B grounding line had receded 10,000 years ago. So I presume the question is why would a floating ice shelf survive for millennia? I suggest that part of that answers lie with how differently circumpolar deep water reaches glaciers on the east and west side of the peninsula. The Weddell Gyre circulates waters in a clockwise direction. Warmer waters shed from eddies in the CIrcumpolar current do not reach the eastern peninsula directly but take a relatively long time to reach first being sent southward across the Weddell Sea and then swept along the coast from east to west during which time it is cooled significantly. Wave action against the Larsen B would be more muted via less wind fetch by the persistent heavy ice that is likewise swept up against the east side of the peninsula
        In contrast, the warmer waters of Circumpolar current approach much more closely to the western coast of the peninsula and Amudsen sea, and in some place ancient troughs deliver warm waters directly to the grounding point before being cooled significantly. Additionally the La Nina/El Nino PDO states have a much more powerful upwelling effect on deep waters on the western side of the peninsula, and those conditions have made the Amundsen Sea a hot spot for basal belting.
        Although all evidence suggests the Larsen B has persisted throughout the Holocene, just north and more directly impacted by the Circumpolar Current, the Prince Gustav Channel Ice Shelf disappeared between 6.0 and 1.9 ka, and the Larsen A Ice Shelf is believed to have been absent at 3.8–1.4 ka, and there is evidence that there was much less ice overall in that region on land and sea during that time.
        I agree that atmospheric conditions probably triggered the Larsen B final collapse. An intense foehn storm occurred as westerly winds that normally go around the peninsula went up and over. The melt ponds were created by that rapid foehn warming, If memory serves that event also slowed the winds that drove the Weddell Gyre which likely suddenly lowered sea level. A sudden sea level drop in combination with downward pressure of foehn winds collapsed an ice shelf that had been slowly thinning through out the warm interglacial. Others also suggest those melt ponds helped weaken the ice shelf’s integrity.

      • Jim, The original post said,
        exploring the Weddell Sea off the coast of Antarctica.
        And the study I linked to said,
        the 2002 Larsen-B Ice Shelf collapse likely was a response to surface warming
        I’m unclear as to the relevance of the Pine Island Glacier (on the other side of the Antarctic Peninsula) or ‘10,000 years ago’.
        BTW, I agree foehn winds likely played a role.

      • Philip I never saw “exploring the Weddell Sea off the coast of Antarctica” The story’s first sentence was “The rapidly melting ice sheets on the coast of West Antarctica are a potential major contributor to rising ocean levels worldwide” I assumed that’s what you referring to

  13. OMG, here we go again.
    Under the WAIS there is a lot going on tectonically speaking, a formative rift valley among some rather big hot spots and vulcanicity but it is difficult to know what is going on and where exactly – for obvious reasons.
    Ice sheets flow, snow accumulated on the ice cap, freezes and pressure, gravity, regelation, water – helps push it out towards the plains, and then to the sea – it is no indicator of ‘warming’ – particularly not the man made variety.
    When, the glaciers calve and bergs sail off into the ‘warmer’ open sea – yeah they melt but so what?
    Ocean gliders are neat but I don’t know what they actually bring to the party…….apart from being great toys for big boys.

  14. You get the impression from the press release that these gliders go some distance over the few hours they are plumbing the depths. If you look at the Supplementary Information for the paper however, the examples of glider tracks are all less than a mile. In reality, the problem with all underwater devices is: where did they go when they were under the water? You know where it went down and where it came up but what happened in between? How does the device fix its position once it has dived? Have they got some magic no-drift inertial system in them?
    Enquiring minds want to know.

    • Navigation
      Radio waves can not penetrate water very far, so as soon as an AUV dives it loses its GPS signal. Therefore, a standard way for AUVs to navigate underwater is through dead reckoning. Navigation can however be improved by using an underwater acoustic positioning system. When operating within a net of sea floor deployed baseline transponders this is known as LBL navigation. When a surface reference such as a support ship is available, ultra-short baseline (USBL) or short-baseline (SBL) positioning is used to calculate where the subsea vehicle is relative to the known (GPS) position of the surface craft by means of acoustic range and bearing measurements. To improve estimation of its position, and reduce errors in dead reckoning (which grow over time), the AUV can also surface and take its own GPS fix. Between position fixes and for precise maneuvering, an Inertial Navigation System on board the AUV calculates through dead reckoning the AUV position, acceleration, and velocity. Estimates can be made using data from a Inertial Measurement Unit, and can be improved by adding a Doppler Velocity Log (DVL), which measures the rate of travel over the sea/lake floor. Typically, a pressure sensor measures the vertical position (vehicle depth), although this can also be obtained from DVL measurements. These observations are filtered to determine a final navigation solution
      http://en.wikipedia.org/wiki/Autonomous_underwater_vehicle#Navigation
      Likewise, it cannot send data when underwater. It just stores the information until it gets a satellite to talk to and then uploads data.

      • So, which method do the gliders use? Dead reckoning and inertial lead to overwhelming error – especially when you consider the low velocity eddies they are supposedly looking for. Acoustic methods require accurate knowledge of sound velocity and detailed information about the environment above and below any transmitters. I think that knowing where an AUV goes underwater with any degree of accuracy requires magic – there are too many uncontrolled variables. A bit like climate science really.

      • From the photo that glider looks like a University of Washington Applied Physics Lab Seaglider. I don’t think Caltech makes ocean gliders. I worked on the UW project for a while and created their 6-DOF Matlab simulation. The UW APL webpage on the gliders states:
        “Dead reckoning between GPS fixes using pitch, roll, heading.”
        They do have a compass that does work underwater I think, and they also have a Kalman Filter that estimates the current drift using data from several consecutive dive/surface sequences. These things to move very slowly, and navigation isn’t that difficult. They could sail them out to Hawaii from Seattle without too much trouble.
        Also note that there is no bladder on the outside of the glider. There is a bladder on the outside of the pressure vessel contained within the hull of the glider, and that is probably what the author was referring to. More info here:
        http://www.apl.washington.edu/projects/seaglider/summary.html

  15. It is difficult to comment meaningfully on this research without knowing at a minimum the difference between sea ice, ice sheets, and ice shelves, or knowing that most of the bedrock beneath the West Antarctic ice sheet is below sea level.
    Appending “Meanwhile: New Antarctic Sea Ice record” at the end is a good way to confuse people further.

  16. I thought this was an interesting article, if warm water is causing melting and therefore contributing to sea levels it would useful to know how and why it got there, it may mean C02 is not adding much if anything to the rise in sea levels.
    These instruments may be a useful tool to help us find out what is happening out there , only if they are used well.
    If C02 is not causing much sea level rise it would be useful to know what is.

  17. The ice shelf would have already caused its SLR due to displacement. Any melting would then have the same effect as sea ice, basically none.

    • If a bit of shelf falls off would that not make it easier for what was behind to move forward and add to SLR?

      • Yes and there is good evidence this is happening.
        Imagine pushing a rowboat in water and then the front runs aground. It will take far more force to push the boat further forward. Similarly, when an icesheet grounds on the ocean floor, it acts as a major brake on the flow of the glacier. When the grounded ice ‘melts’ the glacier accelerates (until it grounds again).
        The real issue here and the reason climatologists want to believe ocean warming and sub-surface melt is causing icesheet retreat, is that if surface melt is found to be the cause then they have the paradox of icesheets melting at the same time sea ice is increasing. A paradox that can be explained by albedo differences between glacial and sea ice, and surface insolation (cloud) changes, but which leaves no room for GHG warming.

  18. So many complain about the reliance on models instead of empirical research and then when a bunch design and use new equipment to actually get some data they still complain.
    As we don’t have non military GPS that can track at a thousand feet down there are some things they can’t measure but they do measure the things we can, and that’s the point. Give kudos for actually going down and finding out.
    Sea ice doesn’t get a mention because it doesn’t deserve one. Continental glaciers meet the sea at some point and what’s being looked at is what happens under the surface, not the top few metres. This sort of knowledge is required if we are to get a handle on the calving process. You can have all the sea ice you want, but if the water is warm 30 metres down, the glacier will still be undercut and calve faster. Some have mentioned the geothermal heat from the volcanoes. How do you think that moves around? Magic? That heat moves around by currents and eddies too.
    “Eddies in the Antarctic Ocean.”
    “Is he….Hmmm”
    *Apologies to Douglas Adams. 🙂

    • thing is we HAVE the argo buoys that already do the up and down depth to surface smapling
      and they do their job
      not quite the agw support theyd wanted though;-)
      so why this new lot of pricy toys for the boys?
      more crap.

      • Measurement is good.
        It allows us to test our theories.
        It stimulates new theories.
        It is related to the real world.
        Would you rather stay at home and play computer games (or models as they call them)?

  19. “Observationally, it’s a very hard place to get to with ships. Also, the warm water is not at the surface, making satellite observations ineffective,” he says.
    —-
    That makes guessing very convenient.
    “Below 40 degrees south there is no law;
    Below 50 degrees south there is no god.”
    —Old Sailors’ saying

    • Below 50 degrees south there is no law
      Below 60 degrees south there is no God
      is the correct quote. 40 degrees south is a breeze compared to the furious fifties

      • Thus the saying.
        You go south into the fifties, and you are into those furies (endless).
        Then again, what would I know I live in Chicago 🙂
        I just like the saying.

  20. Jim Steele, thank you for you reply, that is good information.
    And I wonder if these researchers think what they have found is something brand new ? . . like the currents and eddies haven’t always been there . . . ?
    . . nah,, I’m sure they’re just hyping this for their next grant . . .

  21. Where is the anthropogenic link? I think discovering that ice melts maybe news for some, but it’s happened before.

  22. At least if the glider gets stuck in heavy ice it won’t have to be rescued by ice breakers from three different countries.

  23. The area being studied here is not the Amundsen Sea area where the majority of melting is being claimed. This is off the Antarctic Peninsula where there really has been some warming, most likely due to wind. One has to wonder if any work is being done in the areas with the highest loss of ice.

  24. There are volcanoes under the ice as well as on the sea floor in W Antarctica. There was a recent eruption detected under ice in the region. The assumption that these have no effect is not an excuse to not mention it and even discuss why they are not significant.
    http://www.livescience.com/41262-west-antarctica-new-volcano-discovered.html
    Certainly some scientists think that geothermal heat flow is much greater than most think (or want to think).
    http://www.natureworldnews.com/articles/7488/20140610/thwaites-glacier-west-antarctica-melting-below.htm

  25. Logically if it didn’t break off and melt then it would keep growing and the world would be covered in ice.

  26. I have to say that to me this looks like an honest attempt, using new technology, to try to find out new information in a fairly inhospitable place.
    How other people interpret the results is a different thing altogether.

    • Nice catch.
      What about continental ice that flows from continent after supporting ice at coast has disintegrated?
      I would not declare increasing ice flows from continent impossible just because of bad wording. The important thing is flow. No power could melt continental ice if it stayed where it is.

      • Yes, they’re implying that either the land ice is sliding off the continent faster than “usual”, or that the shelf was inhibiting that movement and it’s now getting out of the way. Both are long stretches, IMO.

  27. As far as I can see the PR doesn’t mention the source of the warm water. Eddies wouldn’t be the (main) source unless they were very fast.

  28. Its is always good to get new data on something not well know , its is always bad to use that data to measure an the unknow past when you simply no idea if the past was like today or not.

Comments are closed.