Support the Arctic Sea Ice Forum and Blog

Author Topic: What the Buoys are telling  (Read 618595 times)

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #850 on: May 16, 2016, 10:36:44 PM »
the camera on obuoy14 is transmitting again  :) not much has changed in the intervening days but I better post the image here for the record, the "movie" still ends in November.

edit: comparing the image with the one from 11. May there is less snow both on the fallen IMB buoy and on ITP89
The warm temperatures on the 12th have caused some melt in the snow. This may be what the AMSR sensor picked up as reported by Wipneus
« Last Edit: May 16, 2016, 10:55:36 PM by Andreas T »

oren

  • Young ice
  • Posts: 4212
    • View Profile
  • Liked: 689
  • Likes Given: 1194
Re: What the Buoys are telling
« Reply #851 on: May 16, 2016, 11:27:03 PM »
Nice catch. It seems like the past five days brought both significant snowmelt as well as lower albedo (or is it just different lighting?)

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #852 on: May 17, 2016, 12:48:59 AM »
I have never been this far north but I would say snow especially changes appearance when viewed under light from different direction and intensity. The photo of today at 19:14 looks into the sun which may well change camera settings as well as intensity of the illumination of the snow.

The attached image is taken at the same time of day as the one from 11.5. so allows better comparison. What is noticeable is the snow surface is less smooth, a sign of slumping in softened snow which has been warmed. Melting of finer ice crystals into coarser grains of snow, increasing density would have that effect. I am aware though that snow in the arctic drifts over large distances which forms more rounded, densely packing snow grains even at low temperatures. Maybe somebody else can give us better first hand experience.
The coarsening of the snow does change albedo by making snow more transparent, allowing sunlight to penetrate further and scatter deeper into the snow and underlying ice and that way increasing absorption. This does give the shadows a more blueish appearance, not sure whether the effect is strong enough here.

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #853 on: May 18, 2016, 09:01:24 PM »
this image from today shows a refrozen crust glistening in the sunshine I think
temperature at that time was below -5oC

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #854 on: May 21, 2016, 08:51:44 PM »
obuoy14 the movie is now available up to the 20.5.  :)
Seeing the developments of the last month roll by is fascinating. The clearing of the camera starts about 3 min in.
A slight addition of snow is visible in the current image

Eli81

  • New ice
  • Posts: 45
    • View Profile
  • Liked: 2
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #855 on: May 22, 2016, 02:13:48 AM »
Thanks for letting us know about the movie update;  fascinating to watch indeed.

I absolutely adore the O-Bouys; they very much satisfy my inner geek, with all the battery parameters, loads, etc. How much do they cost? Do I want to know?...

We need more of them. Lots more.

Has anyone ever thought about crowd funding them? I would love to have one of my own, sponsored by my company. I'm just a small mom and pop outfit, but maybe big corporations that are looking to have a green image would sponsor them more readily.

I guess their longevity is pretty poor? That's unfortunate. What is the longest lived one?

What exactly causes them to die? It seems that they tumble over and drown, even though they're designed to float? Is it a solvable engineering challenge - better stability perhaps? Or more waterproof, so they can just pop back up after being run over? That would probably increase costs significantly, I suppose..

Sorry, just thinking aloud here, but I think my newbie-ness shows through.  :-[ They just seem like such a valuable tool, and it's really depressing to see both that there have only ever been 15 deployed and only one appears alive...

vigilius

  • Frazil ice
  • Posts: 129
    • View Profile
  • Liked: 5
  • Likes Given: 1
Re: What the Buoys are telling
« Reply #856 on: May 23, 2016, 09:02:19 AM »
Eli,

I have held off answering your questions in hopes one of the more senior members of  the forum would chime in, but you can read a lot about these particular buoys and their funding at: http://www.whoi.edu/website/beaufortgyre/home

All of us here share your sentiments, I am sure. Obuouy 15 was just placed last fall and didn't even make it through the winter. Others of the buoys have had adventures lasting in the neighborhood of two years.

Best any of us can do about funding this (last I heard they were near the end of their grant for this particular program) is to vote for politicians who understand the importance of science and don't make fun of NSF grants they don't understand.

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #857 on: May 23, 2016, 09:20:42 PM »
Eli81 i agree and the thought of giving some financial support to something so worthwhile and entertaining has occurred to me too. It would also show in a "put your money where your mouth is is" sort of way that there are people who care about this.

You can read up about the buoys here: http://www.o-buoy.org/?page_id=152

Anne

  • Grease ice
  • Posts: 527
    • View Profile
  • Liked: 7
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #858 on: May 24, 2016, 06:32:13 AM »
Crowdfunding the Obuoys sounds way more realistic than some of the suggestions we've been hearing round here lately. But still massive amounts of money.  Back in 2010, they were talking about $442,395.
http://www.nsf.gov/awardsearch/showAward?AWD_ID=1022773

Anne

  • Grease ice
  • Posts: 527
    • View Profile
  • Liked: 7
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #859 on: May 24, 2016, 06:56:56 AM »
That amount of money would be transient water vapour to Exxon.

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #860 on: May 30, 2016, 10:48:38 AM »
So it would require a substantial response from a large part of this forums membership to fund one Obuoy - I would contribute.
 But another avenue might be to talk to groups which are putting buoys into the arctic which don't have the cameras we like to watch and offer to fund the addition of a webcam to their buoys - that should be more economical?

obuoy14 has been under grey skies for a week now. Temperatures were stuck at or just below -5oC which surprises me. With the ocean below the ice at -1.65oC (assuming IMB2015 is representative there) I would expect temps to rise slowly when there is no cooling at the surface and with clouds reducing longwave losses I would think that is the case when wind is low. (it also is what the weather models predict for that area)

IR images show low "night" (low sun) temperatures on thick ice further east and the snow covered islands of the Canadian archipelago. Maybe some cold air comes from there?
Some warmer air is predicted from the south but on the 5day forecasts this only lasts two days. We will see.
In the view from the camera there has been a persistent dark stretch at the horizon. I wonder whether that indicates an open lead in that vicinity, in the way that low clouds are darker when open water underneath does not reflect light onto their underside. (I have read that the Inuit use(d) this for navigation)
« Last Edit: May 30, 2016, 11:44:30 AM by Andreas T »

mati

  • Frazil ice
  • Posts: 269
    • View Profile
  • Liked: 1
  • Likes Given: 0
Re: What the Buoys are telling
« Reply #861 on: May 31, 2016, 01:01:53 AM »
That amount of money would be transient water vapour to Exxon.

need a post on reddit and a quick starter program set up for continual funding
and so it goes

timallard

  • Frazil ice
  • Posts: 136
  • designer
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: What the Buoys are telling
« Reply #862 on: May 31, 2016, 08:11:26 AM »
So it would require a substantial response from a large part of this forums membership to fund one Obuoy - I would contribute.
 But another avenue might be to talk to groups which are putting buoys into the arctic which don't have the cameras we like to watch and offer to fund the addition of a webcam to their buoys - that should be more economical?
<snip> Good idea .. </snip>

In the view from the camera there has been a persistent dark stretch at the horizon. I wonder whether that indicates an open lead in that vicinity, in the way that low clouds are darker when open water underneath does not reflect light onto their underside. (I have read that the Inuit use(d) this for navigation)
Yes, and and the Inuit knew the shape of their islands from it projected into the sky at times.

They consider the ice state rotten and dangerous now, hunting days greatly reduced from things I've read.
-tom

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #863 on: June 03, 2016, 11:50:50 AM »
IMB2015Fwhich had been silent since the 22. May has transmitted data again :)
http://imb.erdc.dren.mil/2015F.htm
temperatures briefly spiked up to zero but are still hovering at about -5oC similar to Obuoy14
« Last Edit: June 03, 2016, 02:18:51 PM by Andreas T »

Jim Hunt

  • Young ice
  • Posts: 4083
    • View Profile
    • The Arctic sea ice Great White Con
  • Liked: 137
  • Likes Given: 22
Re: What the Buoys are telling
« Reply #864 on: June 03, 2016, 12:42:43 PM »
I'd noticed that too Andreas. Only just realised the web site's suddenly up to date though!



Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #865 on: June 04, 2016, 07:54:14 PM »
Maybe I just have been too lazy to look hard enough but has someone found an easy way to access data from these buoys: http://data.meereisportal.de/gallery/index_new.php?active-tab=buoy

Jim Hunt

  • Young ice
  • Posts: 4083
    • View Profile
    • The Arctic sea ice Great White Con
  • Liked: 137
  • Likes Given: 22
Re: What the Buoys are telling
« Reply #866 on: June 04, 2016, 09:05:39 PM »
Does this work?

http://data.meereisportal.de/gallery/index_new.php?ice-type=buoy&region=n&submit3=display&lang=en_US&active-tab=buoy

I had a look a while ago and couldn't make sense of the data. However you've prompted me to take a closer look again, and DataT for 2015T25 looks as if it's reasonable?
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #867 on: June 12, 2016, 10:06:59 AM »
obuoy14 has shown temperatures near 0oC for a few days but not much melting. The snow on top of the ITP is gone but now some new snow has appeared (yesterday the lens was covered). Along the ITP drifting probably makes it look more substantial, see the small increase at the IMB buoy on the right.

edit: replaced image with clearer one from 7 hours later
« Last Edit: June 12, 2016, 04:27:13 PM by Andreas T »

magnamentis

  • Guest
Re: What the Buoys are telling
« Reply #868 on: June 12, 2016, 10:42:37 PM »
did anyone see that black stripe in the background, too pixelated when zoomed in but could well be open water ( leed ) ? does anyone have an opinion or another explanation, it's not a cloud, that i'm quite sure.

Neven

  • Administrator
  • First-year ice
  • *****
  • Posts: 7034
    • View Profile
    • Arctic Sea Ice Blog
  • Liked: 613
  • Likes Given: 407
Re: What the Buoys are telling
« Reply #869 on: June 12, 2016, 11:51:57 PM »
March of the penguins?  ;)
Il faut comparer, comparer, comparer, et cultiver notre jardin

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #870 on: June 13, 2016, 12:12:36 AM »
when the sun is behind the camera the line along the horizon is light, when facing the camera it is dark. It also has an uneven outline which makes it most likely a ridge of tilted ice where two floes were pushed together.  I have speculated before that darkness of the clouds at the horizon may indicate open water in that direction. The low position of the camera 2m above the ice surface makes it unlikely that water beyond the ridge can be seen from the camera.

Bruce Steele

  • Nilas ice
  • Posts: 1410
    • View Profile
  • Liked: 84
  • Likes Given: 8
Re: What the Buoys are telling
« Reply #871 on: June 13, 2016, 12:36:38 AM »
I don't have ITP buoys to watch so I have been watching this weather data from a dock in Kotzebue sound. The water temperature is taken from a depth of 3.1 meters below mean low water. Water temperatures have risen to 39F today.

http://www.ndbc.noaa.gov/station_page.php?station=RDDA2

There is a long term record and this graph shows how mean monthly temperatures compare to current conditions.

  http://www.ndbc.noaa.gov/view_climplot.php?station=rdda2&meas=st

magnamentis

  • Guest
Re: What the Buoys are telling
« Reply #872 on: June 13, 2016, 12:48:02 AM »
March of the penguins?  ;)

penguins in the artic, that's a good one ROFL

but "spass beiseite" (seriously) perhaps we can find a sat image, just a bit cloudy around. if it were dark grey i had not posted but it seems that pitch black, that raise that suspicion. let's see. enjoy the rest of the sunday

 8)

magnamentis

  • Guest
Re: What the Buoys are telling
« Reply #873 on: June 13, 2016, 01:08:13 AM »
unfortunately as it seems the available sat images do exactly not cover the area where O-Buoy14 is located but looking at the next neighbouring image there seem to be many enough leeds, gapps and whatever these black spots are called, hence the possibility that we are looking at a stripe of open water is at least there.

of course i'm not an experienced sat image interpreter, always ready to learn what else all those black spots
and stribes on that sat image could be.

« Last Edit: June 13, 2016, 01:47:33 PM by magnamentis »

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #874 on: June 13, 2016, 02:40:24 AM »
if I read the pos of Obuoy14 as about 153W 77.7N on the 11th there is a S1A image http://www.polarview.aq/images/106_S1jpgsmall/201606/S1A_EW_GRDM_1SDH_20160611T171312_76CA_N_1.jpg
and on the 9th a fairly clear AQUA http://go.nasa.gov/1Ym540i
yes there are leads open in the area but whether you will see water surface from the cameras position at the distance and over an obvious ridge is another question.

I have marked a recognizable floe in both images with a circle to make cross referencing easier

solartim27

  • Grease ice
  • Posts: 547
    • View Profile
  • Liked: 16
  • Likes Given: 19
Re: What the Buoys are telling
« Reply #875 on: June 13, 2016, 08:02:03 AM »
did anyone see that black stripe in the background,
Just shadows, watch the end of the mp4
FNORD

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #876 on: June 13, 2016, 08:35:40 AM »
seeing the dark line persist under different lighting I now agree with Magnamentis that there is open water visible where the ridge is low enough to see the surface beyond it.
Precise lat/lon information for the buoy seems to be only in the video. This makes it difficult to locate it on a particular floe in the satellite image. Whether the gap is wide enough to show on the satellite is another question, 250m pixels for MODIS could be darkened by a narrower stretch of water, maybe somebody else has better information?
« Last Edit: June 13, 2016, 08:55:00 AM by Andreas T »

magnamentis

  • Guest
Re: What the Buoys are telling
« Reply #877 on: June 13, 2016, 01:50:17 PM »
I have marked a recognizable floe in both images with a circle to make cross referencing easier

thanks for this useful information, i can clearly see that i have to significantly improve my skills as to finding sat imagery. perhaps i shall tap your knowledge base a few times more :-) very much appreciated

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #878 on: June 14, 2016, 03:42:19 PM »
I am hoping for a camera image with more contrast to see what is happening to the snow but surface height seems to be dropping while air temperatures are about zero.
Again this coincides with cloudy skies.
The dark line at the horizon has shifted a bit and varied in size. This fits with changes in azimuth which can be seen at the bottom of the GPS page. A large are of ice will rotate only slowly, faster changes such as seen on the 8th and today are signs of more mobile, smaller floes.

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #879 on: June 19, 2016, 11:48:52 PM »
The "movie" camera image archive still ends on the 20th so I will try to keep images updated here for comparison of different weather conditions with temperature readings. A-team has linked some interesting articles on melt and radiative effect of clouds http://forum.arctic-sea-ice.net/index.php/topic,749.msg80679.html#msg80679
Several commenters here (me included) have noted that warm conditions which lead to melting are often observed at Obuoys when the images show cloud or fog.
We should try to make these observations more systematic than a hunch based on anectotal memory.
I will try to post images  coinciding with satellite overpasses to also relate observations on the ground with the view from MODIS

fairly clear sky, temperature (read from graph) about -3oC at local midday if I am not mistaken
Snow level has dropped a little again, but the glossy refrozen surface seen a month agohttp://forum.arctic-sea-ice.net/index.php/topic,327.msg77220.html#msg77220 has disappeared and snow drifts are in different allignment which suggests fresh snow has been deposited since the beginning of the month.
The rotation (see Azimuth on GPS page) has now been nearly 90 deg since the 14th
« Last Edit: June 19, 2016, 11:58:50 PM by Andreas T »

timallard

  • Frazil ice
  • Posts: 136
  • designer
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: What the Buoys are telling
« Reply #880 on: June 20, 2016, 02:14:01 AM »
<snip>
Several commenters here (me included) have noted that warm conditions which lead to melting are often observed at Obuoys when the images show cloud or fog.
We should try to make these observations more systematic than a hunch based on anectotal memory.
I will try to post images  coinciding with satellite overpasses to also relate observations on the ground with the view from MODIS.
<snip>

A reaction, the fog & clouds make sense they capture LWIR, add in that much moisture it'll hold heat to make it more effective at melting.
-tom

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #881 on: June 20, 2016, 10:42:38 PM »
more clouds and higher temperature, below 0 but above -1 I guess, it would be so much better if that graph would adjust its scale to the smaller temperature range in the summer months.
Those clouds appeared yesterday to be honest and temperatures have risen slowly, so not clear how strong the connection is in this instance.

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #882 on: June 21, 2016, 10:43:24 PM »
todays view is similar to the 19th but temperature is warmer, I'd call it -1oC
wind has increased to 10m/s is that a sign of the coming cylone?

timallard

  • Frazil ice
  • Posts: 136
  • designer
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: What the Buoys are telling
« Reply #883 on: June 22, 2016, 06:24:11 AM »
todays view is similar to the 19th but temperature is warmer, I'd call it -1oC
wind has increased to 10m/s is that a sign of the coming cylone?
Newbie to the datasets, do these buoys measure LWIR specifically or a broadband recording you slice? ... my focus LWIR versus optical & humidity properties vs incident clear values vs melt response, don't know the sensors used seems to matter in home thermal tools my thought.

-tom

oren

  • Young ice
  • Posts: 4212
    • View Profile
  • Liked: 689
  • Likes Given: 1194
Re: What the Buoys are telling
« Reply #884 on: June 22, 2016, 10:57:50 PM »
Something new in today's picture - sunlight!

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #885 on: June 22, 2016, 11:10:14 PM »
unfortunately no radiation measurements on these buoys, IR, LW or SW.  There are automated weather stations which do those measurements.
just look though the tabs at http://obuoy.datatransport.org/monitor#buoy14/weather
Temperatures have to be read out of a graph with 5deg gradations. Annoyingly other graphs adjust their scales automaticaly but temperature has a range of +20 ??? to -40 at this time of year!

today temps have crept above 0 and there is a glaze of wet snow at the surface I think under a clear sky.
we have to guess that incoming shortwave (vivsible and IR) is high and incoming LW low (depends a bit on humidity of higher layers of air but will be lower than under a cloudy sky)
« Last Edit: June 22, 2016, 11:15:33 PM by Andreas T »

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #886 on: June 23, 2016, 10:40:22 PM »
rotation of the floe has changed the sun position for the same time of day but there is very little change in the surface condition. Temperature dropped quickly earlier today with a slight change in wind direction and a rise in relative humidity. The camera lens was obscured by condensation (I guess) or precipitation (although there is no obvious sign of that on the surface

Now temperature is back up just below 0oC

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #887 on: June 24, 2016, 10:33:08 PM »
temperature just above 0oC

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #888 on: June 26, 2016, 10:20:00 AM »
I missed the 20:00 image yesterday but don't think the 21:00 is different earlier in the day it looked like this and the temperature is flat on 0oC. Relative humidity though, which usually drops when temperature rises, has climbed to the maximum it reaches at any time (even in fog and rain I haven't seen an Obuoy report 100%). This coincides with a change in wind direction on the 25th.
The camera shows not much of the surface features in this light reduced in intensity and scattered into a diffuse even illumination with weak shadows.
With a little hindsight from this mornings image it shows the beginning of melt, a slight drop of the snow surface at the IMB buoy this evening this may be clearer.
The indication is nevertheless that melt onset coincides with clouds and seems to depend on advection of humid air (wind from a suitable direction)



Mikko

  • New ice
  • Posts: 2
    • View Profile
  • Liked: 0
  • Likes Given: 0
Re: What the Buoys are telling
« Reply #889 on: June 26, 2016, 12:16:23 PM »
Visible melt of snow must come with clouds because with sun all melt dries out to the air. Sun doesn't build meltponds, it simply makes snow disappear.

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #890 on: June 27, 2016, 08:56:20 AM »
I didn't catch yesterday's 20:00 image it went from the 16:00 image to 22:00 which had something obscuring the view (water drops?) on the lens. Cloud cover has not changed since earlier images.
What stands out is the very flat temperature graph on 0oC and a slight day/night fluctuation on relative humidity which is higher than it has been on recent high temperatures.

This morning the image is still not as clear as I would like to make a definite statement but I think there are the  beginnings of forming meltponds beyond the buoy on the right

Miko can you give more details of why you think that or quantify the effect? The camera images don't show snow disppearing during sunshine as far as I can tell.

oren

  • Young ice
  • Posts: 4212
    • View Profile
  • Liked: 689
  • Likes Given: 1194
Re: What the Buoys are telling
« Reply #891 on: June 27, 2016, 11:42:31 AM »
This morning the image is still not as clear as I would like to make a definite statement but I think there are the  beginnings of forming meltponds beyond the buoy on the right

It's definitely blue that hasn't been there before. Nice catch.

Adam Ash

  • Frazil ice
  • Posts: 302
    • View Profile
    • The 100 metre line
  • Liked: 6
  • Likes Given: 19
Re: What the Buoys are telling
« Reply #892 on: June 27, 2016, 01:18:39 PM »
and bluer still at 20160627 1001
http://obuoy.datatransport.org/monitor#buoy14/camera

and it has been simmering nicely at zero C for a few days now.
http://obuoy.datatransport.org/monitor#buoy14/weather

ghoti

  • Grease ice
  • Posts: 765
    • View Profile
  • Liked: 12
  • Likes Given: 14
Re: What the Buoys are telling
« Reply #893 on: June 27, 2016, 03:52:02 PM »
Is it possible we tend to see melt ponds forming under cloudy humid conditions not because of increased melt but because of decreased evaporation? So similar melt but more water lost to the air under clearer conditions?

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #894 on: June 27, 2016, 08:24:49 PM »
with the "movie" not updated since the 20.5. we don't have a good record of weather and snow height, but the conclusion I draw from looking through the images available there and archived in this thread is that snow level falls not much when the sky is clear and the sun shines. So while I agree that the reduction of relative humidity seen on the sensor in these conditions does allow  higher evaporation/sublimation to take place, the evidence for snow "disappearing" is poor.
In making this statement quite cautious I acknowledge that using the buoys seen from the camera as ablation stakes could be flawed because there are snowdrifts around them which make the snow height against the buoys not necessarily representative of the widespread situation.
The key for seeing the beginning of meltponds now is that the snow height has been reduced to no more than the level at the installation of the buoys in October 2015. The "movie" includes a frame of the installation which shows people moving in snow on the ice (as would be expected in October) but how much we don't know. That we now see a translucent blue at the surface shows that water soaked snow transmits light into the ice rather than scattering it from the many ice / air interfaces of dry snow.
In other words meltwater from "disappeared" snow has been accumulating below the surface.
attached is a still from http://obuoy.datatransport.org/monitor#buoy14/movie

seaicesailor

  • Guest
Re: What the Buoys are telling
« Reply #895 on: June 27, 2016, 08:26:15 PM »
I missed the 20:00 image yesterday but don't think the 21:00 is different earlier in the day it looked like this and the temperature is flat on 0oC. Relative humidity though, which usually drops when temperature rises, has climbed to the maximum it reaches at any time (even in fog and rain I haven't seen an Obuoy report 100%). This coincides with a change in wind direction on the 25th.
The camera shows not much of the surface features in this light reduced in intensity and scattered into a diffuse even illumination with weak shadows.
With a little hindsight from this mornings image it shows the beginning of melt, a slight drop of the snow surface at the IMB buoy this evening this may be clearer.
The indication is nevertheless that melt onset coincides with clouds and seems to depend on advection of humid air (wind from a suitable direction)

Great stuff Andreas. Yet don't you think that it has been casual that we have seen in Modis some clear skies between the storms? Perhaps a bit of sun has helped. It was weeks no sun.

Andreas T

  • Nilas ice
  • Posts: 1125
    • View Profile
  • Liked: 11
  • Likes Given: 2
Re: What the Buoys are telling
« Reply #896 on: June 27, 2016, 08:58:51 PM »
The conclusion I have come to with the still fairly limited knowledge I have is that the big difference between sun and clouds is where radiation is absorbed and emitted.
Incoming shortwave radiation is absorbed over a larger depth of snow and ice. Snow is more transparent to short wavelengths than to the long IR wavelengths which it emits in its thermal radiation. That means even with similar input and output the surface is colder than deeper layers unless the snow temperature is already at melting point.
In that way sunlight contributes to bringing ice and snow temperatures towards melting but is less able to cause surface melt.
IR emitted from the clouds reduces the net longwave loss from the surface (it is absorbed within a very thin surface layer since snow is opaque to these long wavelengths)
The net surplus in the radiative balance does come from the diffuse sunlight scattered by the clouds (less than under clear skies but an addition to a nearly balanced budget. If there is another addition from convection or even condensation that would make the gain in energy larger, also right at the surface.
Advection of warm moist air also means  the "underside" of the clouds, where the downwelling IR comes from, is warmer as far as I know.


Adam Ash

  • Frazil ice
  • Posts: 302
    • View Profile
    • The 100 metre line
  • Liked: 6
  • Likes Given: 19
Re: What the Buoys are telling
« Reply #897 on: June 27, 2016, 10:39:29 PM »
The attached GIF shows view from OBuoy14 on deployment, end of May 2016 (end of the movie) and today.  Clearly some loss of snow, but a long way to go to to the floe's original ice surface.

(Sorry about lack of 'registration' of the images - things have been twisting around in the view...)

Adam Ash

  • Frazil ice
  • Posts: 302
    • View Profile
    • The 100 metre line
  • Liked: 6
  • Likes Given: 19
Re: What the Buoys are telling
« Reply #898 on: June 28, 2016, 02:30:47 AM »
..and definitely a pond.  Looks like more out towards the horizon too...
At 77.8N 146.0W.  Azmith is about 20 degrees, so looking northwards..

And a view of the neighbourhood (VERY approx location suggested by green zone). 
« Last Edit: June 28, 2016, 03:03:57 AM by Adam Ash »

magnamentis

  • Guest
Re: What the Buoys are telling
« Reply #899 on: June 28, 2016, 11:35:07 AM »
..and definitely a pond.  Looks like more out towards the horizon too...
At 77.8N 146.0W.  Azmith is about 20 degrees, so looking northwards..

And a view of the neighbourhood (VERY approx location suggested by green zone).

thanks for the sat image, i was looking for that one and it just confirms what i've tried to say, that eve though the direct location of the buoy looks (looked) like totally intact arctic ice condition it's located in the middle of a big messy i field with floes and leads "en masse"