From the European Space Agency: CryoSat goes to sea
CryoSat was launched in 2010 to measure sea-ice thickness in the Arctic, but data from the Earth-observing satellite have also been exploited for other studies. High-resolution mapping of the topography of the ocean floor is now being added to the ice mission’s repertoire.
The main objective of the polar-orbiting CryoSat is to measure the thickness of polar sea ice and monitor changes in the ice sheets that blanket Greenland and Antarctica.
But the satellite’s radar altimeter is not only able to detect tiny variations in the height of the ice but it can also measure sea level.
The topography of the ocean surface mimics the rises and dips of the ocean floor due to the gravitational pull. Areas of greater mass, such as underwater mountains, have a stronger pull, attracting more water and producing a minor increase in ocean-surface height.
Therefore, instruments that measure sea-surface height incidentally map the ocean floor in previously uncharted areas.
There have been several recent global gravity missions, such as ESA’s GOCE satellite, that provide extraordinarily accurate measurements of gravity at the spatial resolution of hundreds of kilometres.
But CryoSat’s radar altimeter can sense the gravity field at the ocean surface, so that seafloor characteristics at scales of 5–10 km are revealed. This is the first altimeter in 15 years to map the global marine gravity field at such a high spatial resolution.
Recent studies at the Scripps Institution of Oceanography in San Diego, USA, found that the range precision of CryoSat is at least 1.4 times better than the US’s Geosat or ESA’s ERS-1.
They estimate that this improved range precision combined with three or more years of ocean mapping will result in global seafloor topography – bathymetry – that is 2–4 times more accurate than measurements currently available.
“We know more about the surfaces of Venus and Mars than we do about the bathymetry of deep oceans,” said David Sandwell from the Scripps Institution of Oceanography in the US.
“This new mapping from CryoSat will revolutionise our understanding of ocean floor tectonics and reveal, perhaps, 10 000 previously uncharted undersea volcanoes.”
Most satellite radar altimeters such as the one on the joint CNES/NASA/Eumetsat/NOAA Jason-2 follow repeated ground-tracks every 10 days to monitor the changes in ocean topography associated with ocean currents and tides.
CryoSat’s 369-day repeat cycle provides a dense mapping of the global ocean surface at a track spacing of over 4 km. Three to four years of data from CryoSat can be averaged to reduce the ‘noise’ due to currents and tides and better chart the permanent topography related to marine gravity.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
I would have thought that there were many factors influencing sea height. Shallow water/ deep water, density of the surface floor, planetary attraction, density of the mantle, effect of latitude on the sea level (thinking here of the Earth’s rotation), varying density of sea water itself (would dense sea water provide a gravitational attraction similar to the upper mantle and reduce the contour relationship ?).
Talk about proxies for proxies. This is an example of experimental scientists doing what they do best, using ingenuity to extract some measure of data from a previously hidden haystack. If they can just report the wonders of their discoveries, and not try to attach it to any political agenda, then they deserve the kudos they will get.
The Apollo13 and Hubble repair missions are examples of what good experimental science can achieve. Can this thing tell if I need to clean the bottom of my swimming pool ?
This is very interesting as well as remarkable.
I hope data is not abused.
That’s interesting. Yes, the geoid. Uhmm….. 2-4 times accurate? I’ll have to check, but I hope the ice thickness tech isn’t the same which went into the estimation of the Himalayan glacial measurements. -4 +/-20gt.
As to moving it to sea-level measurements….. I’d keep a wary eye. Envisat “died” right after they “corrected” their data, even data they never presented before! Now both Jason’s are seemingly stuck in stupid. I’ve chronicled the slow “adjustments” to Jason II here….. https://suyts.wordpress.com/2012/04/18/the-quickening-jason-ii-getting-in-the-act/
But anyone can go here, http://www.aviso.oceanobs.com/en/news/ocean-indicators/mean-sea-level/products-images/ and see some very strange things occurring, or rather, not occurring. Just knock off any adjustments (click on any radio button with the word “not” in its description) to see how strange this all is. Did they all collide up there?
From above – “But CryoSat’s radar altimeter can sense the gravity field at the ocean surface,”.
I did not know we understood enough about what gravity is to be able to detect in this fashion. I presume there is some proxy method of measurement being used here. If there is anyone that can shed some more light on the subject?
Thanks.
Excellent! A better understanding of the ocean floor topography and tectonics is highly desirable. “….10,000 previously uncharted undersea volcanoes”??? Oh, Baby!!!!!!!
So they are going to use the data from the parts of the orbit they previously didn’t use to do other science. That is ok. I only object when they start removing sensors from their primary mission to do some tertiary junk projects then miss the primary data.
……wind strength, direction, SOI changes.
I came across some impressive logic here as NASA tries to explain the 2010 drop in sea level.Check the top right diagram, water fell in Brazil and Australia reducing sea height……mmmm… where did it go after that ?
It would be really nice, to get a better picture, of the total volcanic activity happening and where. A few spot checks, should confirm the results definitively, I would think. GK
It’s ESA; situated in hyper-PC-warmist EU. They have rewritten the entirety of the Envisat record because the satellite wouldn’t play ball. They will do what it takes to prove what needs to be proven.
I have to read the apropriate links, but this smells. Somehow, the satellite designed to measure ice is now going to be reasigned to measure water? How can this be? Perhaps the ice measurements were not only wrong, but unadjustable?
As McIntyre would say, watch the pea. But that is wrong advice. Yes, it is a shell game the Warmistas are playing. But, the key to the shell game is that the pea is under none of the cups. No point in watching the pea; that is the whole scam – the audience watches the hand that supposedly hols the pea while it is in fact not in play, in the other hand.
@ur momisugly Truthseeker: What the satellite is doing is like what a gravimeter does when measuring the gravity field on the surface of the earth. Gravity anomaly maps are used in oil/gas exploration and in mining to identify possible places for exploration/exploitation. Since it would be cost prohibitive to cover the oceans with the detail and speed the satellites can do, this is a good idea and will provide much needed information and understanding of the true contours of the ocean bottom.
DirkH,
Correct.
Here is Envisat data following “adjustment”:
http://wattsupwiththat.files.wordpress.com/2012/04/envisat2bhide2bthe2bdecline.png
Here is Envisat’s unadjusted data:
http://wattsupwiththat.files.wordpress.com/2012/04/msl_serie_en_global_ib_rwt_nogia_adjust.png
Isn’t this the same thing the GRACE satellite pair is supposed to be doing, topography (even underwater) by detecting gravity? Isn’t GRACE doing a good enough job? Do they need confirmation?
Although I wonder about how this is supposed to work. GRACE measures gravity by precisely measuring the distance between the satellites, when traveling over a larger mass the larger gravity force moves the satellites slightly closer together. By physics the satellites should also move slightly closer to the ground.
It says “…CryoSat’s radar altimeter can sense the gravity field at the ocean surface…” which it seemingly does by measuring the water height, higher water indicates greater mass under the surface. Some modeling with several parameters later, the sea floor map is generated. But CryoSat should also move slightly closer to the ground over a larger mass, and CryoSat will only be measuring height.
Oh well, crank it through a supercomputer, use calculated parameters (aka “educated guesses”) as needed, call it science. Don’t forget to publish the error margins.
I’ve looked at a web site of the ocean floor recently. Supposedly the best detail ever.
Without having to go look for an answer, can someone tell me why there are many straight lines and 90 degree angles etc on the ocean floor. Some of the features look impossible to be natural.
The ocean levels are primarily rising due to the production of water from fossil aquifers plus water formed when fossil fuels are combusted. The rise rate is 2.4 mm per year from the no or slow to recharge aquifers and 0.2 from combustion water formation for a total rise of 2.6 mm per year (year 2000 datum point). Due to water tables declining the production rate of the fossil water has been declining a bit.
TheEnvisat “adjustments” need to critically reviewed.
JFD
The problem with this technology is that it doesn’t seem to account for the changes on the ocean floor. The assumed geoid (flood contours on the surface) must change. And if people look at where the sea levels are rising, (according to the satellites) it is in the exact spots where we’d expect the geoid to change. Now, this is a crude discussion, but just look at the graphics if nothing else. http://suyts.wordpress.com/2011/06/25/discussion-so-far/ Clearly, there’s something here for more than one or two people. I quit bothering with it because as Dirk and Smokey have affirmed, it doesn’t really matter, they’ll lie anyway.
But, there’s your gravitational pull, there’s your geoid….. exactly where all the underwater volcanoes are. There’s your sea level rise.
greymouser70 says:
May 30, 2012 at 8:38 pm
—————————————
Thank you for attempting to answer my question, but looking at how a gravimeter operates (http://en.wikipedia.org/wiki/Gravimeter), there is no way that such a device orbitting many, many kilometers above the planet can accurately get readings from either the surface of the ocean or the ocean floor. It must be doing something else and that means it is using a proxy measurement of some kind. My question still stands, and by the look of some of the comments here, I am not the only one.
It actually looks like Cryosat is not going to be able to measure the sea ice thickness accurately enough, one of its primary missions. I’ve been looking at some of its raw data and it changes so much between the tiny swaths available in each orbit (waves, tides, etc) that it looks like it will only be able to provide some indication of seasonal averages. Maybe they are trying to find new purposes to justify the budget required.
kadaka (KD Knoebel) says:
May 30, 2012 at 8:43 pm
Isn’t this the same thing the GRACE satellite pair is supposed to be doing, topography (even underwater) by detecting gravity? Isn’t GRACE doing a good enough job? Do they need confirmation?
Although I wonder about how this is supposed to work. GRACE measures gravity by precisely measuring the distance between the satellites, when traveling over a larger mass the larger gravity force moves the satellites slightly closer together. By physics the satellites should also move slightly closer to the ground.
It says “…CryoSat’s radar altimeter can sense the gravity field at the ocean surface…” which it seemingly does by measuring the water height, higher water indicates greater mass under the surface. Some modeling with several parameters later, the sea floor map is generated. But CryoSat should also move slightly closer to the ground over a larger mass, and CryoSat will only be measuring height.
Oh well, crank it through a supercomputer, use calculated parameters (aka “educated guesses”) as needed, call it science. Don’t forget to publish the error margins.
——————————————————————————————————–
1. A radar altimeter does not measure gravity, it measures distance between the satellite and the surface of the ocean.
2. Grace measures the gravity field.
3. It seems counter intuitive that higher water height means greater mass underneath. If the water is being attracted to the greater mass then there should be a depression in the overlying water column.
4. Radar altimeter data actually penetrates the surface of the ocean as old rad alt generated images show sea floor expressions and underground tunnels in shallow water environments.
5. Seems like the scientists have dumbed this down to the point where rational people can’t make sense of their comments.
Robert of Ottawa says:
May 30, 2012 at 8:18 pm
I have to read the apropriate links, but this smells. Somehow, the satellite designed to measure ice is now going to be reasigned to measure water? How can this be? Perhaps the ice measurements were not only wrong, but unadjustable?
———————————————————————————-
Robert,
If you have an optical measurement to reflect off the ice (laser) and a radar altimeter to reflect off the conductive ocean’s surface you can measure ice thickness. Radar does not “see” ice because ice is not conductive.
If you decide to use a radar altimeter to measure the surface of the ocean then there is no difference between radar and laser. So mapping very small variations in ocean height is better accomplished with a laser-based device (shorter wavelength, higher accuracy).
http://www.esa.int/esaLP/ESAQ5JPV16D_LPcryosat_0.html
Underwater volcanoes are not simple things. Everyone always assumed the Emperor Seamounts were a geostationary blowtorch from the mantle that recorded the movement of the Pacific Ocean floor. The graphic above makes it look more like a midocean ridge than the series of islands in the current Google Ocean. I wonder which is right. I wonder how much a gravity line dance along this linear feature biases measurements that can only see the surface.
“This new mapping from CryoSat will revolutionise our understanding of ocean floor tectonics and reveal, perhaps, 10 000 previously uncharted undersea volcanoes.”
Surely not!
And after Bob Ward and his Thermogeddonists chums “proved” that Ian Plimer doesn’t know what he’s talking about?
\sarc
Robert of Ottawa says:
May 30, 2012 at 8:18 pm
I have to read the apropriate links, but this smells. Somehow, the satellite designed to measure ice is now going to be reasigned to measure water? How can this be? Perhaps the ice measurements were not only wrong, but unadjustable?
============
Really, both ice elevation and sea level are the same measurement — the distance between the satellite’s antennae and the reflecting boundary between the earth’s surface and the atmosphere. The big difference between Cryosat and, for example, Jason would presumably be orbital inclination which controls how close the satellite flies to the poles. If you are going to measure Arctic sea ice elevation, you want a very high inclination orbit that actually flies over the polar ice rather than a lower inclination orbit that only skims the Arctic/Antarctic.
That said, this article is a press release and was very likely written by someone with only the haziest idea of what the satellite is actually doing — after consulting with one or more people who hopefully do know something. It’s not clear to me that modestly better vertical resolution and substantially lower pass to pass horizontal intervals than Jason (design goal I believe of 1 cm vertical resolution) is somehow going to open up new vistas (vistae?) of scientific knowledge. But what do I know?