Fleuve avec glace de l'espace

By Phil Plait | January 20, 2010 7:21 am

It’s been weeks since I’ve seen clear ground here in Boulder; we’ve had snow and ice for a long time. You’d think I’d be sick of it and wouldn’t want to see any more, but then you either don’t know me well, or you haven’t seen this beautiful image from NASA’s Aqua satellite:

aqua_stlawrenceriver

[Click to embiggen.]

This image, taken on January 17, 2010, shows thin ice forming in the St. Lawrence river in Quebec. I love the swirls of ice, forming along the eddies and flow of the water.

Aqua is an Earth-observing satellite designed to monitor our planet’s water cycle as it orbits at an altitude of 700 kilometers. The camera used in this image is the MODIS, or Moderate Resolution Imaging Spectroradiometer. It can observe in a whopping 36 different wavelengths, from visible to infrared. It has a maximum resolution of 250 meters per pixel — I find that a bit funny, given that we have probes orbiting the Moon and Mars with resolutions a thousand times higher. But each was designed to do a specific job, and for Aqua, 250 meters is good enough. Clearly, it’s enough to produce stunning images like this one.

CATEGORIZED UNDER: Pretty pictures, Space

Comments (28)

Links to this Post

  1. 0.01 Ohm/km « Dr. Goulu | March 27, 2010
  1. Nady

    Wow! That’s my home. Beautifull, thanks!

  2. Dragon

    I am sure there are Satellites orbiting the Earth that have resolution greater than any probe sent into deep space. These Satellites are simply the domain of government agencies and their capabilities are not for public consumption.

  3. Gerard

    At two to three pixels wide, those are some awesome freeways in Quebec.

  4. Michelle R

    And I just have a new wallpaper!

  5. Awesome picture! We Canadians know how to do it right! :)

    @ Dragon:
    I heard the US Gov’t has satellites that can read the fine print at the bottom of newspaper ads, in the dead of the deepest darkest night, in the basements of 25 story buildings! ;)

  6. Michelle R

    @Gerard: Yea sure. From space. Did you ever DRIVE on them? They’ll wreck your car.

  7. And we are getting more. One of the few benefits of being unemployed is I do not have drive in the stuff that often.

  8. Colin J

    Cool! The body of water in the lower right is the Bay of Chaleur (Bay of Heat ironically enough) and that is where I grew up in New Brunswick, just a bit off the corner of that image. when you embiggen it, I can see my hometown of Bathurst. Great picture. I was home last week, and the talk is that it’s unusual that the bay isn’t solidly frozen as it usually is this time of year.

  9. StubbyGB

    Remember that 250m per pixel gives a much larger area of coverage for the same number of pixels than LRO. Different applications have different requirements, looking at indevidual rocks on the moon needs much higher resolution than looking at oceanic water flow patterns on earth.

  10. So, can somebody tell me why the swirls look like water comes *up* the river, and then freezes? Does the seawater (which I expect could be colder than the freshwater freezing point) come in with the tide and cause this icing up?

    I got out of engineering because software is *so* much easier….

    Thanks!

    Dennis

  11. JT Montreal

    @Gerard & @Michelle:
    Actually, the lines look too straight for our roads. I think they’re Hydro cuts (for people not familiar with them, if passing a high voltage line through forest, you cut away plenty of forest away on each side). Up there, the roads don’t get big enough to warrant cutting away much forest (and besides, the bigger road is on the south shore, and you can’t see them at all), and besides, you want to leave some on either side of the road so the tourists don’t see the clearcutting.

    I’m just happy to see the Chic-chocs so clearly. I’ve been skiing there a bunch of times.

  12. Philippe

    Having holiday-ed (is that a word) in the area a fair bit, I can confirm that those are Hydro cuts. They are even visible on sat images taken during the summer. Go check out Google Maps, you’ll see the lighter green of the cuts thru the darker, mostly coniferous, forest.

    The itty bitty tiny sqiggly white lines, those are the roads…

  13. Jim Salacain

    Picking a resolution for a system like this is a big optimization problem. When you decide you need very tight spectral bands that equates to fewer photons per band. lower photon counts means you need to integrate longer to get an adequate signal to noise ratio. Since the satellite is moving WAY fast you can only integrate photons for a short time. Take too long and the satellite moves past the target faster than you can image it. The only other thing you can do is make the detectors bigger so the suck up more photons. In order to get high resolution with big detectors (in long wavelengths like IR) you need big optics. Big optics means big rocket… etc… etc… For ocean studies most “structures” you’re going to be looking at are going to be huge so low resolution isn’t a problem. Area coverage and radiometric discrimination are more important.

    my $0.02

  14. Markle

    So, can somebody tell me why the swirls look like water comes *up* the river, and then freezes? Does the seawater (which I expect could be colder than the freshwater freezing point) come in with the tide and cause this icing up?

    I got out of engineering because software is *so* much easier….

    Thanks!

    Dennis

    I suspect that might be the subject of a Thesis in the future.
    There’s some massive stuff to be looked at with Thermo- and Saline- clines

  15. Those ice vortices remind me of some forms of von Karman vortices. Beautiful!

  16. philippec

    The swirls are cause by floating ice chunks or slush, because at that point in the river the currents, tides, waves, winds, and so on are too strong to allow the river to freeze solid.

    Also, the width of the river you are seeing in the image varies between 20km and 50 km (the point on the right, just before it realy widens), so that is a lot of water to freeze…

    My 0.02 CND cents…

  17. Steven

    Awesome!

    I’m very familiar with this terrain. I live farther east closer to the tip of the Gaspe peninsula, and not too far from Perce!

  18. 5. MichaelL Says: “I heard the US Gov’t has satellites that can read the fine print at the bottom of newspaper ads, in the dead of the deepest darkest night, in the basements of 25 story buildings!”

    Plus they can be “moved into position” to hover over the building and provide real-time IR imaging of all the people in the building triangulated to which floor they’re on!

    Hey! I saw it on “24.” It must be real!

    - Jack

  19. Johnny B Good

    From my perspective, which is one of a boater familiar with these waters in summer, I can tell you that yes, the salted water can get below 0C, this even in mid-summer over there, but at some point in winter it also turns in ice and what you see there as blue, is all seawater. Though a respectable amount of freshwater comes down from the Great Lakes, this freshwater quickly gets mixed into the seawater downstream of the Saguenay river (the notch on the North shore where the water abruptly turns dark) and mainly because the Labrador current also rushes upstream from the ocean on the North shore to upwell in front of Tadoussac. This makes for the currents to go West on the North shore and East on the South shore in this part of the river. This kind of “conveyor belt” behavior must be what causes those eddies.

  20. 10. Dennis Rockwell

    The spot where the river really starts to widen at the right of the picture is the beginning of the Gulf of St. Lawrence, which is better thought of as ocean than river. Sea and river water mixing occurs all along the bit you can see in the photo so yes, the tides and sea water do move up the portion of the river you can see in the photo.

  21. Chris A.

    @Marko (14)

    “There’s some massive stuff to be looked at with Thermo- and Saline- clines”

    I think the word you’re looking for is “halocline” (spatial variation of salinity).

  22. Brian Too

    I saw a show a couple of years back on this region of Canada. They were talking about Greenland sharks which are a type of large deep water shark that only frequents very cold (Arctic) waters.

    I was fascinated to discover that parts of the St. Laurence and it’s tributaries are cold and deep enough that Greenland sharks will go there. We know this because every once in a while a fisherman will catch one. Usually they are very surprised!

    The St. Laurence isn’t considered Arctic waters and yet it has these creatures living in it.

  23. French grammar nazi here: “Fleuve avec glace vu de l’espace”. Or, as good, “Fleuve glacé vu de l’espace”. What you wrote literally translates as “River with space ice”.

    PS: I can see my aunt’s house on that picture (if the resolution was high enough that is).

  24. Messier Tidy Upper

    ^ I like that literal translation! ;-)

    (Pictures River Tamm from ‘Firefly’ & ‘Serenity’ standing on the surface of a comet .. )

    Cool photo in both senses of the word. :-)

  25. Michelle R

    @11. JT Montreal: Oh, you’re right. Just checked it out on googlemaps.

    That would’Ve been pretty wide roads…

  26. Johnny B Good

    @20 robert brown

    It’s a common mistake, unanimously made by the locals (and even by the wikipedia map though the reported coordinates in the article are correct) to say the gulf starts in Pointe-des-Monts (that big cape on the North shore). The real gulf is nowhere to be seen on this pic and you have to go to the NASA picture enlargement to see the western part of the gulf. So, the Gulf officialy start at 64deg30W on the North shore (a bit East of the Jacques-Cartier River and West of the Mingan Islands) on a line including the Western tip of Anticosti and back to 64deg30W on the South shore which is the village of Anse-aux-Griffon on the Forillon Park. So before you crossed East of this line, you’re still in the Estuary. My apologies to the locals, you just moved back on the River. ;)

    I’ll give you that, once in the middle of it and not seeing either shores, it feel gulflike, sealike or oceanlike enough. It’s 80 nautical miles wide when you leave it to enter the gulf! The real one…

  27. amphiox

    At 250m resolution, wouldn’t a 2-3 pixel wide line be like half a kilometer across?

    If so, them be some pretty impressive roads for some pretty impressive cars.

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