Cryosat ice mission returns first science data

NOTE: The image below is NOT sea ice thickness, but ocean topography.

Radar data from the European satellite has been used to make a map of ocean circulation across the Arctic basin.

Cryosat’s primary mission is to measure sea-ice thickness, which has been in sharp decline in recent decades.

But its ability also to map the shape of the sea surface will tell scientists if Arctic currents are changing as a result of winds being allowed to blow more easily on ice-free waters.

“Nobody really knows how the Arctic is going to behave as the ice retreats, but we do anticipate that significant changes will occur,” said Dr Seymour Laxon, a Cryosat science team member from University College London, UK.

“This is just the first data, and it shows we now have the tool to monitor what is happening,” he told BBC News.

[Cryosat] carries one of the highest resolution synthetic aperture radars ever put in orbit.

The instrument sends down pulses of microwave energy which bounce off both the top of the Arctic sea-ice and the water in the cracks, or leads, which separate the floes.

By measuring the difference in height between these two surfaces, scientists will be able, using a relatively simple calculation, to work out the overall volume of the marine ice cover in the far north.

WUWT carried the story of the Cryosat launch and testing  in several articles:

CryoSat-2 exceeding expectations

Posted on July 6, 2010

From the European Space Agency 070110 Participants at the Living Planet Symposium have been hearing about ESA’s most recently launched mission, CryoSat-2. In orbit for almost three months, the satellite is in excellent health with scientists very encouraged by the … Continue reading →

CryoSat passes first operational tests

Posted on April 13, 2010

From the European Space Agency, it looks like CryoSat-2 is working well. I’m sure we are all looking forward to seeing what the results are. ESA’s ice mission delivers first data 13 April 2010 ESA’s CryoSat-2 has delivered its first … Continue reading →

Cryo-sat launch successful

Posted on April 8, 2010

Successful launch for ESA’s CryoSat-2 ice satellite From the European Space Agency: 8 April 2010 ESA PR 07-2010. Europe’s first mission dedicated to studying the Earth’s ice was launched today from Kazakhstan. From its polar orbit, CryoSat-2 will send back … Continue reading →

Full story about the current data from BBC here

About these ads

52 thoughts on “Cryosat ice mission returns first science data

  1. Cryosat’s primary mission is to measure sea-ice thickness, which has been in sharp decline in recent decades.

    Alarmist crap. There has been no measurement until the last decade that I am aware of, and there have been several times in the last 100 years where there has been observably less ice (see pics of subs at the north pole).

  2. News from Nunavit today on the CBC. Frobisher Bay is ice free. The Innuit can’t go out hunting over the ice. There is no ice.

    Polar bears, being much lighter than Innuit, are having no trouble . They can walk across the memory of arctic ice.

    Maybe the new ice age has to do with the cubes in the drinks at the Petrolium Club in Calgary.

  3. There will always be ice in the winter. And it will fill the land-limited bowl. The winds, in terms of blowing ice around or apart, become important during the melt and summer season. I wish the media would get that distinction.

  4. I wonder if they will actually send someone to check if their “relatively simple” calculation is working correctly.

    It doesn’t seem like anything relatively simple to me. Neither the ice nor the water is flat, unlike their sweet diagram. Not every low point will be water either.

    Still, I suppose the algorithm will be exactly imprecise, which means we can learn something from the anomalies. [ sigh ]

  5. What do you want to bet that they will compare this to some other, older measurement, and decide “it’s worse than we thought”?

  6. Radar pulse has been around for a while (serious use began in WWII). Most radar specialists have this one fairly well understood. I for one, am excited about this and will be following it like a hawk on a rabbit, dry on day-old bread, baby to nipple, fox to the hen house, stud to studette, a woman to a diamond, a snake to the grass, and a redheaded Irish lass to laced coffee on a witch tit cold morning.

  7. Cryosat’s primary mission is to measure sea-ice thickness, which has been in sharp decline in recent decades.

    Umm, Psst Guys, There has been zero trend in global sea ice extent in recent decades. This fact is not in dispute. Warmie predictions that the ice would melt were and are an epic fail. Trying to find ice that is “thinner then it was before” is not going to work for you as ya’ll pinned your hopes on extent. Al, and Phil and Keith and Micheal and James and perhaps Dr. Laxon all need to accept that they have a problem.

    I understand that the Betty Ford clinic might be considering a new program to rehabilitate scientists who fall of the AGW wagon. I think they are calling it Hockey Stick Addiction Syndrome. Perhaps if Dr. Laxon and friends all go together they can get a group discount. You never know, if it works for Linsay Lohan… oops never mind.

  8. CryoSat 2 data will forever change our understanding of sea ice, and so the release of new data is an exciting time for those of us (professional and non) who want to know everything we can about sea ice dynamics. For the first time in history we’ll soon be able to get a reasonable measurement of actual arctic wide sea ice VOLUME as opposed to relying on models. That, in itself, is most exciting…

  9. Oh my god,

    What the Hell is going on here,

    The warming east of Greenland ( Hudson-Bay) is a result of the negative NAO/AO. In Europe it have some of the coldest day ever but it must mean that the warm is on another Place..

    or look here:

    Typical AO/NAO negativ Anomalys

    greets from Germany

    REPLY: scroll down on the main page, we already covered this – Anthony

  10. ““Nobody really knows how the Arctic is going to behave as the ice retreats, but we do anticipate that significant changes will occur,” said Dr Seymour Laxon”

    Well Dr. Laxon you seem to be assuming that the sea ice is going to retreat when the past few years it has expanded. Maybe as a scientist you should wait till you have your data and let it tell you what is happening rather than decide what your data will show before you even collect it.

  11. The satellite measures the thickness of ice floes by the difference in return time of radar pulses from the top of the ice and the adjacent sea surface. No problem. But how does it measure ice thickness 100s or 1000s of kilometers from any open water? I can imagine an algorithm for that, but can it *measure* ice thickness without nearby open water?

  12. OK, so I’ll bite.

    What means “Gravitational Level” ? And is that “Gravitation” adjusted for the earth’s rotation; seeing as how the earth does rotate, and that would affect local “gravity”.

    Why do these graphs always raise more issues than answers ?

  13. But its ability also to map the shape of the sea surface will tell scientists if Arctic currents are changing as a result of winds being allowed to blow more easily on ice-free waters.

    Allowed? Man is controlling the winds now? /head desk

  14. Robert M. says:

    “Umm, Psst Guys, There has been zero trend in global sea ice extent in recent decades.”

    ___

    Umm…not so fast there Robert. A simple glance at the global sea ice chart tells you that you’re wrong:

    Why are you wrong? Simply because the seasonal loss of sea ice in the N. Hemisphere has been greater than the seasonal gain of sea ice in the S. Hemisphere…i.e. a steeper down averaged against a less steep up equals a down…and so I’m sorry to be such a “downer” on your little conjecture, but the data tell the story.

  15. DesertYote says:
    December 22, 2010 at 2:19 pm
    Mmmm, tasty data; needs a little less spin though
    ______

    Tasty Data? Spin Dough? When I was in ccllege and made Pizza for a living I was King of spinning the dough and never had one stick to the ceiling (on accident).

  16. George Smith —

    “Gravitational Level” is technically called “geoid”. It is the theoretical surface where the strength of gravity is constant. Since the Earth is not uniform, the geoid bulges up where it is denser and down where it is less dense. The actual shape can be quite complex. There are places in the US where the equipotential surface or geoid varies several meters over a few tens of kilometers. Satellites use a smoothed geoid with features no smaller than a few kilometers.

    The geoid is harder to determine than “sea level”, but is more dependable because it doesn’t change with tides, winds, currents, etc., and is available in the middle of continents.

    The Equivalence Principle tells us that all accelerations are equal in the sense that the source doesn’t matter, whether gravity from mass or motion caused by force. Since the geoid follows a constant acceleration value, the rotation of the Earth is factored in automatically.

  17. So when can we expect to see some pretty graphs using this new data? Anything similar to The Cryosphere Today page out there yet? It will be interesting to see how it compares to PIPS and PIOMAS. It may put to rest the debate over which one is more accurate when actual measurements are available for comparison.

    I agree R. Gates. The fact that we will now know, as opposed to just guessing (or believing), is exciting unto itself. While it may be a time for some to gloat at the opposition, let’s hope that measurements reveal a non-issue with sea ice. Not just because I am sceptical of AGW but because then we can focus on more pressing concerns like actual pollution, poverty and corruption.

    MrC

  18. Crysosat has no way of measuring snow depth. All they can do is use modeled snow depths. So their data is simply another model, Since Real data + model = model.
    They will then be able to reach any conclusion they wish.

  19. Every piece of new equipment is subject to new interpretation. In the absence of any reference point, the interpretation will be in the eye of the beholder. If a grant is at stake, the interpretation will be…you guessed it…dire, indeed.

  20. R. Gates

    “…and so I’m sorry to be such a “downer” on your little conjecture, but the data tell the story.”

    Oh, let me guess. It was CO2 what did it?

    Yes, there is a decline, but could you tell me which portion is natural, and which portion is mine and your fault, please?

  21. Sad really that as a child of the 60’s science was the spine of my upbringing.

    I really should be excited about Cryosat but I’m sure it will go the same way as Satellite MSU, ARGO or indeed “simple” RSB. The data will disappear in a haze of “re-analysis products” unless it promotes the pre-determined storyline.

    Sad really that having grown up with the moon landings I should, in 2010, come to see science as just very expensive PR to be auctioned off to the highest bidder. Very sad.

  22. Ric Locke says:
    December 22, 2010 at 2:30 pm
    Ric, surely the line of constant acceleration will be changed by accumulation of sea water etc due to winds, tides and pressure systems and so will vary with time?
    I’m nearly certain that if this data doesn’t show what the warmies want, doubt will be cast on the instruments or the assumptions behind the interpretation of the results.
    But, what the heck, it’s only taxpayers money. Send more.

  23. “Why are you wrong? Simply because the seasonal loss of sea ice in the N. Hemisphere has been greater than the seasonal gain of sea ice in the S. Hemisphere…i.e. a steeper down averaged against a less steep up equals a down…and so I’m sorry to be such a “downer” on your little conjecture, but the data tell the story.”

    Not so fast R. Gates.. the little graph you linked only goes to 1979. Please post one that goes back a couple of hundred years and maybe we can see even a short term trend.

  24. MrCannuckistan says:
    December 22, 2010 at 2:35 pm
    So when can we expect to see some pretty graphs using this new data? Anything similar to The Cryosphere Today page out there yet? It will be interesting to see how it compares to PIPS and PIOMAS. It may put to rest the debate over which one is more accurate when actual measurements are available for comparison.

    I agree R. Gates. The fact that we will now know, as opposed to just guessing (or believing), is exciting unto itself. While it may be a time for some to gloat at the opposition, let’s hope that measurements reveal a non-issue with sea ice. Not just because I am sceptical of AGW but because then we can focus on more pressing concerns like actual pollution, poverty and corruption.

    _______
    You are ever the optimist, and only we could wish the world (of humans) worked in such a logical way. Regardless of where you fall on the AGW warmist/skeptic spectrum, and whether you think declining Arctic sea ice is a “problem” or not, we all know that the more we measure and study things, the more “problems” we’ll find. I’m not suggesting at all that we stop measuring and studying things, as I’m as curious as the next person, but if you give a man a hammer, suddenly the whole world becomes a nail…I’m just sayin’….

  25. Ron says:
    December 22, 2010 at 3:20 pm
    “Why are you wrong? Simply because the seasonal loss of sea ice in the N. Hemisphere has been greater than the seasonal gain of sea ice in the S. Hemisphere…i.e. a steeper down averaged against a less steep up equals a down…and so I’m sorry to be such a “downer” on your little conjecture, but the data tell the story.”

    Not so fast R. Gates.. the little graph you linked only goes to 1979. Please post one that goes back a couple of hundred years and maybe we can see even a short term trend.
    ____

    Nice of you to bud…uh, I mean, join in here Ron. The specific time frame that was the topic of conversation was the “past few decades” which we clearly have data for and which clearly shows a trend– down, for global sea ice, specifically because the large decline in the Arctic is greater than the modest (very modest) gain for the Antarctic. Robert M. said:

    “There has been zero trend in global sea ice extent in RECENT DECADES.” (emphasis mine) Which is flat out wrong…and I thought it proper to point that out.

    But again, thanks for joining in.

  26. “Not so fast R. Gates.. the little graph you linked only goes to 1979. Please post one that goes back a couple of hundred years and maybe we can see even a short term trend.”

    This really is crucial. Studying the sea ice is interesting in itself, but as far as ANTHROPOGENIC GW goes, it can say very little. We dont have any data at all to base trends on. Anomalies since ’79 are meaningless. They could weaken or strengthen the AGW hypothesis, but only by very little. I wish the field was more open, curious and less politicized.

  27. R. Gates says:
    December 22, 2010 at 2:18 pm

    (Robert M. says:
    “Umm, Psst Guys, There has been zero trend in global sea ice extent in recent decades.”

    Why are you wrong? Simply because the seasonal loss of sea ice in the N. Hemisphere has been greater than the seasonal gain of sea ice in the S. Hemisphere…i.e. a steeper down averaged against a less steep up equals a down…and so I’m sorry to be such a “downer” on your little conjecture, but the data tell the story.

    R.Gates. Don’t get me wrong here, this isn’t an attack. You don’t seem to be a “party line spoutin’ eco-loon”…

    Does your mental model model of the Arctic include the AMO? It is just that looking at the (unadjusted) long standing weather station records available for the N. Atlantic one might believe that the AMO is what controls Arctic ice. That is to say that air temps and ice volume are the product of “warm” ocean currents rather than CO2 (hey, firm believer in atmosphere as a continuation of ocean by other means). As with the last peak in the ’40s they may well be heading the other way soon. What is your view?

    (Different set-up “down south” and I fail to see a connection between the two ATM – not to say that there isn’t one)

  28. Is the graph corrected for the inverse barometer?

    Spokes around the pole look a little bit unphysical too.

    Was there a strong wind blowing off the west coast of Greenland when the data was gathered, piling up the water against Baffin Island?

    How does the satellite account for changes in sea level due to tide between orbits?

    I think we should be told.

  29. “”””” Ric Locke says:
    December 22, 2010 at 2:30 pm
    George Smith –

    “Gravitational Level” is technically called “geoid”. “””””

    Ric, Thanks for the explan. When you say it is the “theoretical” surface; are you talking from some model theory; or izzat an actual experimental observation; and how do they observe that; they must have some sort of absolute accelerometer; and yes I presumed that such a gizmo, if it exists would read net net net final gees, no matter the components.

    And if one actually knew the exact shape of this geoid; isn’t that something one wouldn’t want some people who aren’t too friendly, to know ??

    Can they measure it accurately enough say to keep up with all the ocean bottom (and land) volcanism ?

  30. Ed Caryl says:
    December 22, 2010 at 2:32 pm
    Just in time to watch the ice increase again. I wonder how they will explain that?”

    No problem at all. Just like Moonbat et al. are spinning the record snowstorms in the UK into the AGW narrative, they will craft increasing sea ice into that narrative as well. They will claim they’ve predicted it all along ANC that it’s due to warming elsewhere. The hotter areas of the globe cause more evaporation at the poles which removes heat and causes freezing. This creates altered wind patterns across the attic that accelerate the evaporation which causes an ice growth spiral. The hotter it gets, the more ice you get, spiraling put of control. And you can be sure it will be worse than they thought.

  31. The following link plots arctic sea ice thickness from 1948 to 2004 using piomas type modeling.

    http://psc.apl.washington.edu/zhang/IDAO/retro.html#Satellite_ice

    Looking at the graph at the bottom of the page in the above link it is estimated during a twenty five year period from 1950 to 1975 sea ice volume grew by 10 x 10 <12 cu. meters during an period of negative NAO like we have started to see since last year.

    http://ioc3.unesco.org/oopc/state_of_the_ocean/atm/nao.php

    I suspect the cryostat 2 has already demonstrated significant thickening since last year but are waiting to decide how to spin it. I believe the short arctic summer that allowed sea ice extent almost to reach normal in March is somehow tied to the negative NAO.

  32. I don’t know when that pic was taken, but it doesn’t bode well for ground truth observations. Warmer water expandes and colder vice versa. So could someone explain why the ocean is lower around greenland where the water is the warmest, and highest towards alaska where it’s coldest?

  33. George: It’s a combination of measurements and theory — they measure until they can fit a relatively simple shape. Yes, there are precision gravitometers. Geologists use them all the time, but the usual tool for determining the shape of the geoid is a pendulum, which always hangs normal to the surface of the geoid. Nowadays we can measure the orbits of satellites accurately enough to determine the geoid, so field measurements are still done but are on the way out.

    That being the case, it’s pointless to try to keep it any kind of secret. Countries used to have their own theoretical geoids, but once it became possible to do one for the whole world the surveyors of practically every country cooperated. Even during the height of the Cold War, US and USSR surveyors collaborated on calculating the geoid. The last major revision of the world geoid was in 1984 — if you have a GPS you may have seen “WGS-84″ in the tech data; it stands for “World Geodetic System”. The heights shown by GPS (and GLONASS) are above the geoid, modified by a database of differences between terrain height and geoid.

    Minor revisions and refinements continue. The world isn’t rigid on the scale we can now measure (centimeters or less — one recent modification changed the polar semidiameter of the Earth by a tenth of a millimeter). The latest work I know of is Earth Geodetic Model 2008, which differs from the WGS-84 geoid by a meter or so in some places. One reason I take things like the article cited here with a good-sized grain of salt is that they rarely or never specify what the reference surface they’re using is. EGM84? EGM96? EGM08? The differences among them are roughly the same size as the variances shown on the map, and I’ve now been out of the business long enough to have lost track of the details. Maybe the satellite is refining the geoid, which is after all “synthetic sea level”, rather than saying anything about ocean height or ice thickness!

    Mike Borgelt — no, sea water isn’t massive enough, and there isn’t enough of it to affect geoid measurements at the ten-centimeter level. It might make a difference of less than a millimeter.

    Regards,
    Ric

  34. Dan in California says:
    December 22, 2010 at 2:01 pm
    The satellite measures the thickness of ice floes by the difference in return time of radar pulses from the top of the ice and the adjacent sea surface. No problem. But how does it measure ice thickness 100s or 1000s of kilometers from any open water? I can imagine an algorithm for that, but can it *measure* ice thickness without nearby open water?

    Take a look at this, bottom half, zoom in a little and you’ll see plenty of leads with open water, typical view for the summer and early fall.

    http://rapidfire.sci.gsfc.nasa.gov/realtime/single.php?T101972325

  35. This is a tool to understand the Earth’s climate better. Understanding the dynamics of the climate is important. The changes in the ENSO and AMO cause significant alterations to the other weather patterns.

    Knowledge is the key. This should help.

    John Kehr

  36. JEROME says
    —————
    several times in the last 100 years where there has been observably less ice (see pics of subs at the north pole).
    ————–
    As far as I am aware it is common for the arctic ice to be discontinuous and so a sub surfacing at the north pole tells you only about the conditions where the sub surfaced. It tells you nothing about the conditions elsewhere. As in a few hundred feet away.

    Since the sub was looking for an open spot ice free areas could be quite small.

    So claims about knowledge ice conditions over hundreds of years amount to wishful thinking.

  37. Kokomo says
    ————

    It doesn’t seem like anything relatively simple to me. Neither the ice nor the water is flat, unlike their sweet diagram. Not every low point will be water either.
    ————-
    Seems simple to me.
    It’s the old ice berg thing. 9/10ths is under water.
    So the satellite measures the height at a point on a grid. Multiply the height by 9 to get the depth. Add the height and depth to get the thickness. Multiply by the grid area to get the volume of the local cube. Add up all the cubes on the grid. You now have the total volume. Done.

  38. LT;
    Just to bring you up to speed, the relevant surface for the ice is the water. Which may or may not be visible nearby to the radar. If the grav field has raised or lowered the water but you can’t tell, which height are you going to measure by 9, exactly?

  39. Steve Pearce:

    I have actually looked at a weather map lately, although the report I referenced is from a CBC reporter in the North. See A. Watts comment a few below mine ; been there done that .

    Still mild here in Nova Scotia. Raining for Christmas, 40 F 40 mph wind. It does feel cold walking the dogs, soaking wet into a North East wind but it is really warm here (mild in Ottawa too { I looked at a weather map on TV } – the world’s coldest Capital) .This is to continue for a while. Maybe another storm Monday. One would almost think that the North Atlantic is warmer than historic levels and is spinning unusually warm, windy storms at us.

    Ridiculous! Noone has ever predicted unusual storm activity from global warming.

  40. 3×2 says:
    December 22, 2010 at 3:49 pm

    R.Gates. Don’t get me wrong here, this isn’t an attack. You don’t seem to be a “party line spoutin’ eco-loon”…

    Does your mental model model of the Arctic include the AMO? It is just that looking at the (unadjusted) long standing weather station records available for the N. Atlantic one might believe that the AMO is what controls Arctic ice. That is to say that air temps and ice volume are the product of “warm” ocean currents rather than CO2 (hey, firm believer in atmosphere as a continuation of ocean by other means). As with the last peak in the ’40s they may well be heading the other way soon. What is your view?

    ________
    Undoubtedly their are natural planetary oscillations of various periods such as the NAO, AMO, etc. that affect the arctic sea ice extent, area, and volume. Added to that are the solar oscillations, and on top of that are the astronomical oscillations such as the basic Milankovitch cycles, etc. GCM’s take all these known natural oscillations into account pretty well (with some notably exceptions, which is the source of my modest skepticsm about the the true nature the late 20th century warming). Be that as it may, GCM’s have long forecast that we’d see the first significant signs of AGW in the Arctic through seasonal sea ice decline, rapid warming, melting of permafrost, etc. and I do believe we are seeing this occur (still modulated, of course, by other natural oscillations). At the end of the day, I do happen to believe it is very likely we will see an ice free summer Arctic some time this century far earlier than the year 2100 as GCM’s were forecasting only a few years ago. Around 2030 is my current target date and the cause of this, as factored into the GCM’s is the rapid rise in CO2 over the past few centuries combined with other positive feedbacks such as the release of methane from melting permafrost, warming peat bogs, etc. While I am NOT currently a believer in C AGW, with the C being of course “Catastrophic”, I do think it more likely than not that basic physics behind, and notion that the 40% rise in CO2 since the 1700’s is affecting our climate is sound. What it will actually mean for life on earth, and specifically for humans, is not something I’ve been considering as of yet, as my basic thrust over many years was trying to get a grasp on the question of “is it happening?” before moving on to “so what are the implications?”.

  41. Odd. You would think they would like to verify the CryoSat-2 findings, and put out extra buoys.

    Only three buoys appear to be active…

    http://imb.crrel.usace.army.mil/newdata.htm

    2010E, 2010F, 2010H are all close to Alaska, Bering Straight.

    2010C and 2010G, with no recent data, are near Canada.

    I recall that in other years there were more active buoys with a better distribution. Nothing at all near the pole this year.

    2009F appears to be active but not on the new data page:

    http://imb.crrel.usace.army.mil/2009F.htm

    The new graphs sure seem fuzzy (compare them to 2009F)

    Who knew that you could adopt a buoy?
    http://imb.crrel.usace.army.mil/2010E.htm (Adopted Buoy: Richmond Middle School, Hanover, NH. )

    Regards,
    Bob

  42. LazyTeenager says:
    December 22, 2010 at 11:23 pm

    Seems simple to me.
    It’s the old ice berg thing. 9/10ths is under water.
    So the satellite measures the height at a point on a grid. Multiply the height by 9 to get the depth. Add the height and depth to get the thickness. Multiply by the grid area to get the volume of the local cube. Add up all the cubes on the grid. You now have the total volume. Done.

    Not sure it will turn out to be that simple. When those “flat” idealised sheets get crushed up by wind and currents they will tend to become mounds. If the dominant winds force the ice toward a shore then vast areas will mound up giving a false impression of ice depth. Conversely winds forcing the ice toward the Atlantic might look a little more as per the diagram unless they are riding large N. Atlantic waves of course. Then if the sheets are held firm in mounds there would be deposition from the atmosphere to account for. Even 30cm of snow/ice x your constant of 9 is a lot of false ice depth. Either way I don’t think it will be simple.

  43. Bob Tatz says:
    December 23, 2010 at 8:27 am
    2009F appears to be active but not on the new data page:

    http://imb.crrel.usace.army.mil/2009F.htm

    2009F was the Russian research station NP-37 which was abandoned in June, it appears to be still active because the data from the latest station (NP-38, aka 2010H) has been added to it.

  44. 3×2 says:
    December 23, 2010 at 10:43 am
    Not sure it will turn out to be that simple. When those “flat” idealised sheets get crushed up by wind and currents they will tend to become mounds. If the dominant winds force the ice toward a shore then vast areas will mound up giving a false impression of ice depth.

    No they still give a true indication of depth because for every meter above the water surface there will be ~9 below.

  45. Phil;
    You still must be able to SEE the nearby water. If the ice coverage is solid and continuous, you lose your reference point. As the gravity map shows, the sea is not flat.

Comments are closed.