Support the Arctic Sea Ice Forum and Blog

Author Topic: What the Buoys are telling  (Read 505327 times)

ghoti

  • ASIF Middle Class
  • Posts: 662
    • View Profile
Re: What the Buoys are telling
« Reply #1700 on: August 05, 2017, 04:54:51 PM »
Note that the irradiance measured is "PAR". That is Photosynthetically Active Radiation (PAR) or just the wavelengths absorbed by chlorophyll. The total irradiance will be significantly higher since it also includes infrared, green, and ultraviolet. Also the chlorophyll they are measuring is absorbing PAR before it reaches the sensors. So energy input is actually higher than the 30ish W/m2

Neven

  • Administrator
  • ASIF Governor
  • *****
  • Posts: 4394
    • View Profile
    • Arctic Sea Ice Blog
Re: What the Buoys are telling
« Reply #1701 on: August 05, 2017, 06:44:53 PM »
That's pretty awesome, no ?

You can say that again, Rob. I'll have to dive in some more on the buoy stuff and latest developments at some point.
Il faut cultiver notre jardin

greatdying2

  • ASIF Middle Class
  • Posts: 574
    • View Profile
Re: What the Buoys are telling
« Reply #1702 on: August 05, 2017, 09:46:21 PM »
That's pretty awesome, no ?

Super cool!

One interesting thing is that although solar irradiance peaked on June 20, there has been -- as Rob points out -- no obvious reduction in water column or in-ice PAR irradiance since then (and perhaps the opposite).
The Permian–Triassic extinction event, a.k.a. the Great Dying, occurred about 250 million years ago and is the most severe known extinction event. Up to 96% of all marine species and 70% of terrestrial vertebrate species became extinct; it is also the only known mass extinction of insects.

Rob Dekker

  • ASIF Upper Class
  • Posts: 1002
    • View Profile
Re: What the Buoys are telling
« Reply #1703 on: August 06, 2017, 04:32:54 AM »
Note that the irradiance measured is "PAR". That is Photosynthetically Active Radiation (PAR) or just the wavelengths absorbed by chlorophyll. The total irradiance will be significantly higher since it also includes infrared, green, and ultraviolet. Also the chlorophyll they are measuring is absorbing PAR before it reaches the sensors. So energy input is actually higher than the 30ish W/m2

Thanks gothi ! I did not realize that.
I've been looking for a multiplier to relate "PAR irradiance" to full spectrum irradiance.
I found that PAR is is typically defined as the 400 nm to 700 nm spectrum, which is where about 50% of the energy resides :
https://en.wikipedia.org/wiki/Photosynthetic_efficiency
That would suggest a 2x multiplier and potentially 2 cm/day of bottom melt.

However, there is a part within that spectrum (green) where plants reflect the light, so when you loo k at the active radiation, PAR may be just 33% of full spectrum radiation :
https://en.wikipedia.org/wiki/Photosynthetically_active_radiation
Which would suggest a 3x multiplier and potentially 3 cm/day of bottom melt.

Ultimately the multiplier depends on how exactly the sensors' raw data is translated to PAR irradiance.
So, Jim, I have a favor to ask :
Since you are already in contact with Victoria Hill, could you ask her if there is a simple multiplier to translate PAR irradiance to full spectrum irradiance in these WARM buoy data ?
Even a ballpark number would help in determining bottom melt potential for light that shines through the ice.

Also, please ask her what we (as a community) could do to support deploying more of these WARM buoys. After all, the information these buoys return is very important in determining the one unknown that can not be measured directly otherwise, yet still ultimately important to the fate of Arctic sea ice : bottom melt of Arctic sea ice...
« Last Edit: August 06, 2017, 10:57:01 AM by Rob Dekker »

Jim Hunt

  • ASIF Governor
  • Posts: 3421
    • View Profile
    • The Arctic sea ice Great White Con
Re: What the Buoys are telling
« Reply #1704 on: August 06, 2017, 03:23:51 PM »
Jim, I have a favor to ask

I have passed on your message, although I doubt that I'll receive a reply over the weekend.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Rob Dekker

  • ASIF Upper Class
  • Posts: 1002
    • View Profile
Re: What the Buoys are telling
« Reply #1705 on: August 07, 2017, 08:51:54 AM »
Thanks Jim !

Rob Dekker

  • ASIF Upper Class
  • Posts: 1002
    • View Profile
Re: What the Buoys are telling
« Reply #1706 on: August 07, 2017, 09:00:47 AM »
Super cool!

One interesting thing is that although solar irradiance peaked on June 20, there has been -- as Rob points out -- no obvious reduction in water column or in-ice PAR irradiance since then (and perhaps the opposite).

Indeed, in-ice and under-ice irradiance over July appears to be fairly constant.
I pulled up anther WARM buoy (W-3), this one from 2015, which shows this profile :



That suggests that irradiance under ice is highest, and fairly constant, during July and August, then tapers off quickly in September. That kind of makes sense : As the ice is melting it become more transparent, and thus lets more light through, which compensates for the reducing insolation above the ice during July and August.

ghoti

  • ASIF Middle Class
  • Posts: 662
    • View Profile
Re: What the Buoys are telling
« Reply #1707 on: August 07, 2017, 05:41:21 PM »
The 2017A and 2017B data has been updated but the front page is showing last week's thickness numbers. When you look at the graphs for each it tells a different story.

2017A shows complete overlap of top and bottom sensor position clearly indicating no ice thickness.

2017B shows continued top and bottom melt at roughly the same rate as the week before.


Jim Hunt

  • ASIF Governor
  • Posts: 3421
    • View Profile
    • The Arctic sea ice Great White Con
Re: What the Buoys are telling
« Reply #1708 on: August 07, 2017, 06:52:58 PM »
2017A shows complete overlap of top and bottom sensor position clearly indicating no ice thickness.

I beg to differ. IMHO 2017A is now clearly bobbing up and down in its self made melt hole, which makes it a bit tricky to discern the actual thickness of the remains of the floe it was stuck in until recently.
« Last Edit: August 07, 2017, 06:58:41 PM by Jim Hunt »
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

ghoti

  • ASIF Middle Class
  • Posts: 662
    • View Profile
Re: What the Buoys are telling
« Reply #1709 on: August 07, 2017, 07:35:24 PM »
I beg to differ. IMHO 2017A is now clearly bobbing up and down in its self made melt hole, which makes it a bit tricky to discern the actual thickness of the remains of the floe it was stuck in until recently.

Yes I'd agree that from the graph it appears both top and bottom sensors rose 40ish cm on August 3rd or so. Now the top sensor is giving readings of 0cm which suggests no measurable freeboard. The bottom sensor continued to show steady declines in thickness until about yesterday when it showed about 10cm then started to bounce around. So I'd still say between 10cm and zero thickness but the 10cm would have required melting to suddenly stop.

Not that the difference at this point is material. The bottom melt rate seems to have been 15cm/week to this point. It is either 0 now or 0 next week.

Tor Bejnar

  • ASIF Upper Class
  • Posts: 1669
    • View Profile
Re: What the Buoys are telling
« Reply #1710 on: August 07, 2017, 07:41:54 PM »
Amazing the camera is pointing to a 'stable' icy view!
Arctic ice is healthy for children and other living things.

Jim Hunt

  • ASIF Governor
  • Posts: 3421
    • View Profile
    • The Arctic sea ice Great White Con
Re: What the Buoys are telling
« Reply #1711 on: August 09, 2017, 10:51:26 AM »
In the continuing absence of SeaIceSailor's excellent animations, here's the latest IMB buoy temperature profiles. I don't think 2017A is down to zero just yet! 2017B's floe is now below 1 meter thick.

http://GreatWhiteCon.info/resources/ice-mass-balance-buoys/summer-2017-imb-buoys/
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

ghoti

  • ASIF Middle Class
  • Posts: 662
    • View Profile
Re: What the Buoys are telling
« Reply #1712 on: August 09, 2017, 04:00:54 PM »
I don't think 2017A is down to zero just yet! 2017B's floe is now below 1 meter thick.

Last image from the WARM buoy near 2017A is from August 2, 2017. It may have met a watery end...

The last WARM buoy image seems to show ice with patches of open water and is annotated "open water!". In the profile you show is thermister 0 in the air with 2-4 in the water and 5,6,7 in the last vestiges of ice?

Jim Hunt

  • ASIF Governor
  • Posts: 3421
    • View Profile
    • The Arctic sea ice Great White Con
Re: What the Buoys are telling
« Reply #1713 on: August 09, 2017, 04:03:23 PM »
Last image from the WARM buoy near 2017A is from August 2, 2017. It may have met a watery end...

The pushpins only get updated in batches every week or two. It may not have!
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

vhill

  • ASIF Lurker
  • Posts: 2
    • View Profile
    • Bio-Optical Research Group
Re: What the Buoys are telling
« Reply #1714 on: August 09, 2017, 04:22:38 PM »
Hi, this is Victoria Hill. You have been discussing some of the data from my WARM buoys.

I'm happy to answer any questions that you might have about these systems. Now that I know that people are actually looking at the data, I will make sure to update my website with the daily images more often!

To answer a couple of questions that were raised. The surface camera appears to be looking at the sky, see attached image. This camera is on the sidekick which is hopefully going to float once the melt pond is deep enough. This is the reason I have started uploading the underwater images instead.

All the data is freely available and I am happy to work with anyone who is interested in using or seeing more of the data. At the moment, I'm not seeing much warming, but I expect that to change once the ice breaks up a bit more.

Hyperion

  • ASIF Citizen
  • Posts: 202
  • Admiral Franklin of the McGillicuddy Highland Navy
    • View Profile
Re: What the Buoys are telling
« Reply #1715 on: August 09, 2017, 06:14:59 PM »
In the continuing absence of SeaIceSailor's excellent animations, here's the latest IMB buoy temperature profiles. I don't think 2017A is down to zero just yet! 2017B's floe is now below 1 meter thick.

http://GreatWhiteCon.info/resources/ice-mass-balance-buoys/summer-2017-imb-buoys/

Gosh that water looks warm. Isn't  2017b collocated with itp95? its not showing water above about -1.5 at the surface though the halocline has all but collapsed despite at 84nth 13.6east it is well inside the pack and barely moved in a week. With a big bundle of heat building from 75m down.
Policy: The diversion of NZ aluminum production to build giant space-mirrors to melt the icecaps and destroy the foolish greed-worshiping cities of man. Thereby returning man to the sea, which he should never have left in the first place.
https://en.wikipedia.org/wiki/McGillicuddy_Serious_Party

oren

  • ASIF Upper Class
  • Posts: 1713
    • View Profile
Re: What the Buoys are telling
« Reply #1716 on: August 09, 2017, 07:15:49 PM »
Hello Victoria Hill, and thank you so much for making these buoys' data available, and for the courtesy of posting here. Buoys are a lifeline to getting actual data about the ice, which is not available via satellites and models, so we are all very keen to look at every deployed buoy (sadly, not too many these days).

Jim Hunt

  • ASIF Governor
  • Posts: 3421
    • View Profile
    • The Arctic sea ice Great White Con
Re: What the Buoys are telling
« Reply #1717 on: August 09, 2017, 08:11:57 PM »
Hi, this is Victoria Hill.

Welcome Victoria. You beat me to it! I was just about to post this extract from your recent email:

There is no simple way to get from PAR to a full spectrum irradiance. Unfortunately, it is like trying to separate paint, once you have mixed all the colors up. However, I do have some sensors on the string that are measuring irradiance at three wavelengths, 412, 443 and 555 as well as PAR, depths, 5, 10 and 20 m. This does enable me to get an idea of the spread of the light through the spectrum, and I have used a modeled surface spectrum, propagated through sea ice (using Bonnie Light’s coefficients) and then normalized to my data to estimate spectral irradiance under the ice.

Regarding supporting more deployments, community use of the data is very important to my NSF program (Arctic Observing Network), if people use the data, then it proves its usefulness.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Neven

  • Administrator
  • ASIF Governor
  • *****
  • Posts: 4394
    • View Profile
    • Arctic Sea Ice Blog
Re: What the Buoys are telling
« Reply #1718 on: August 09, 2017, 10:18:21 PM »
Welcome to the ASIF, Dr Hill. Thanks for the work you do and your willingness to answer questions.
Il faut cultiver notre jardin

Rob Dekker

  • ASIF Upper Class
  • Posts: 1002
    • View Profile
Re: What the Buoys are telling
« Reply #1719 on: August 10, 2017, 07:19:07 AM »
Thank you Victoria, for checking in with the ASIF !

I find your WARM buoys extremely interesting and useful.
Since they have temperature and salinity sensors down the tether, they mimic the information normally obtained by ITP buoys.
And since the have in-ice and under-ice irradiance sensors, they provide and indirect measurement of bottom-melt, thus providing the information normally obtained by IMBs (like 2017A).

Thus, your WARM buoys are like two buoys at once, as long as we can obtain full-spectrum under-ice measurements (not just PAR). And it is in that regard that I have some questions :

You mentioned in an email to Jim :
However, I do have some sensors on the string that are measuring irradiance at three wavelengths, 412, 443 and 555 as well as PAR, depths, 5, 10 and 20 m. This does enable me to get an idea of the spread of the light through the spectrum, and I have used a modeled surface spectrum, propagated through sea ice (using Bonnie Light’s coefficients) and then normalized to my data to estimate spectral irradiance under the ice.

Couple of questions on that, with the purpose of finding out how we can determine full-spectrum irradiance from the sensors on your buoys :

1) Do your WARM buoys have 4 different sensors (412, 443, 555 nm and a separate PAR sensor) ? Or just 3 sensors (412, 443, 555 nm) and you calculate PAR from that ?

2) If PAR irradiance data is obtained from a separate sensor, then what is the wavelength sensitivity distribution of that sensor ?

3) To get from sensors to PAR in W/m^2, which algorithm did you use ? And would it be hard to adjust the algorithm so that it produces an estimate of full-spectrum irradiance ?

4) I've been looking for the irradiance raw data in your "level 1 data" in the WARM 6 data page
http://psc.apl.washington.edu/UpTempO/BuoyInfo.php?cbuoy=9080&bname1=UpTempO%202017
However, that "level 1 data" does not include data from the irradiance sensors. Could you add that ?

Besides these questions about the irradiance sensors, I am a bit puzzled by the irradiance data from some of the WARM buoys. For example, the WARM 3 data (from 2015) :



Here we see that during June, and part of July, in-ice PAR is very large (some 200 W/m^2 on average) but under-ice PAR is very small (mostly less than 10 W/m^2).
Starting from the second half of July things return to normal with in-ice PAR at some 50 W/m^2 and under-ice PAR is some 40 W/m^2.

What happened there in June ? Is there a logical explanation for the huge difference between in-ice and under-ice PAR ?

Jim Hunt

  • ASIF Governor
  • Posts: 3421
    • View Profile
    • The Arctic sea ice Great White Con
Re: What the Buoys are telling
« Reply #1720 on: August 10, 2017, 08:20:25 AM »
The halocline has all but collapsed.

Perhaps you could highlight on that ITP 95 T&S plot what you consider to be evidence for your assertion?
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Rob Dekker

  • ASIF Upper Class
  • Posts: 1002
    • View Profile
Re: What the Buoys are telling
« Reply #1721 on: August 10, 2017, 08:42:34 AM »
ITP95 is on its way out of the Arctic and into the Atlantic



As all the prior buoys that followed that path, the halocline starts to disappear and more salty Atlantic water takes its place.

Rob Dekker

  • ASIF Upper Class
  • Posts: 1002
    • View Profile
Re: What the Buoys are telling
« Reply #1722 on: August 10, 2017, 08:48:19 AM »
Oops. I see that Jim already replied on ITP95.

slow wing

  • ASIF Middle Class
  • Posts: 571
    • View Profile
Re: What the Buoys are telling
« Reply #1723 on: August 10, 2017, 08:51:26 AM »
The halocline has all but collapsed.

Perhaps you could highlight on that ITP 95 T&S plot what you consider to be evidence for your assertion?
Had just been musing on the potential benefit of having a third profile contour plot to go with the temperature and salinity ones, namely, the water density profile. (Or could instead plot the gradient of the density.)

That should be easily derived from the information already in the other two and would show more directly where the density gradient was small i.e. 'halocline all but collapsed'.

Is that third profile contour ever plotted along with the other two?
« Last Edit: August 10, 2017, 08:57:45 AM by slow wing »

Jim Hunt

  • ASIF Governor
  • Posts: 3421
    • View Profile
    • The Arctic sea ice Great White Con
Re: What the Buoys are telling
« Reply #1724 on: August 10, 2017, 09:15:43 AM »
Oops.

No probs Rob. You've added additional relevant information!
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Jim Hunt

  • ASIF Governor
  • Posts: 3421
    • View Profile
    • The Arctic sea ice Great White Con
Re: What the Buoys are telling
« Reply #1725 on: August 10, 2017, 09:19:04 AM »
I will make sure to update my website with the daily images more often!

Thanks very much Victoria. Here's the August 8th image:



Unless I'm very much mistaken open water is getting very close to your WARM buoy. What happens next? Does it float for example?
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Tor Bejnar

  • ASIF Upper Class
  • Posts: 1669
    • View Profile
Re: What the Buoys are telling
« Reply #1726 on: August 10, 2017, 06:10:59 PM »
I don't believe I ever looked at O-Buoy 14's weather tab before.  Is the intermittent data due to solar power issues?  And what is "uptime"?  Are the Lithium battery spikes 'telling'?
Arctic ice is healthy for children and other living things.

woodstea

  • ASIF Lurker
  • Posts: 87
    • View Profile
Re: What the Buoys are telling
« Reply #1727 on: August 10, 2017, 06:41:59 PM »
It's intermittent because there is no longer sufficient battery power to keep things running when the solar panels can't generate electricity from the available light. The gaps will continue to lengthen as the days get shorter. On the GPS graphs you don't see the gaps, just a lack of movement, which can be misleading.

vhill

  • ASIF Lurker
  • Posts: 2
    • View Profile
    • Bio-Optical Research Group
Re: What the Buoys are telling
« Reply #1728 on: August 10, 2017, 10:49:01 PM »

Hi Rob, to answer your questions.

1) Do your WARM buoys have 4 different sensors (412, 443, 555 nm and a separate PAR sensor) ? Or just 3 sensors (412, 443, 555 nm) and you calculate PAR from that?

The buoys have the Satlantic OCR 550 multispectral sensors in the irradiance configuration. Our wavelengths are 412,443 and 555 plus a PAR channel, so PAR is measured separately
http://satlantic.com/ocr500

3) To get from sensors to PAR in W/m^2, which algorithm did you use? And would it be hard to adjust the algorithm so that it produces an estimate of full-spectrum irradiance?

The sensor inside the PAR channel has a filter in front of it that lets through all light between 400 and 700 nm. This means that we can't get a full spectrum from this kind of instrument. The full spectrum sensors are very expensive, hence my choice to use these. There is a general conversion from W m-2 to umol m-2 s-1 and this coefficient 4.6. It's 100% accurate as you need to know the wavelength of the photons to get an accurate conversion.

4) I've been looking for the irradiance raw data in your "level 1 data" in the WARM 6 data page
http://psc.apl.washington.edu/UpTempO/BuoyInfo.php?cbuoy=9080&bname1=UpTempO%202017
However, that "level 1 data" does not include data from the irradiance sensors. Could you add that ?


Yes, I can. Now I know that people are interested I can work to put up whatever info you would like.

Besides these questions about the irradiance sensors, I am a bit puzzled by the irradiance data from some of the WARM buoys. For example, the WARM 3 data (from 2015) :



Here we see that during June, and part of July, in-ice PAR is very large (some 200 W/m^2 on average) but under-ice PAR is very small (mostly less than 10 W/m^2).
Starting from the second half of July things return to normal with in-ice PAR at some 50 W/m^2 and under-ice PAR is some 40 W/m^2.

What happened there in June ? Is there a logical explanation for the huge difference between in-ice and under-ice PAR ?

This is hard to tell with out surface pictures. As all sensors see decreased light during this time, it probably snowed, decreasing light penetration. However the in water sensors decreased by much more than the in ice, so;
Guess 1: If in water absorption increased that would cut down the light on those sensors, absorption would increase if phytoplankton increased. However, I don't see a large increase in chlorophyll during this time.
Guess 2: Spatial differences in ice conditions. Visualize the sensors field of view. The in ice sensors are very close to the ice surface so their light field is influenced by a very small patch of ice, if the snow here melts they will see more light. The in water sensors, however, are further from the ice and so the light here is influenced by a much large patch of ice. If snow cover in the larger area was thicker than directly over head this might cause the larger reduction.
It's often very frustrating to be unable to know for sure what is happening, this is why we added the surface camera this year.


Here is the diagram of the buoy, at deployment the float is offset from the ice hole to prevent shading of the in ice sensors. As the ice melts the buoy slips through the hole, with all the sensors becoming 3 m deeper in the water. Once it melts out it will float, most of the previous ones made it through the summer and were frozen back in.

woodstea

  • ASIF Lurker
  • Posts: 87
    • View Profile
Re: What the Buoys are telling
« Reply #1729 on: August 11, 2017, 01:34:03 AM »
Lots of snowmelt today at O-Buoy 14, and warm weather on the way for the weekend.

Hyperion

  • ASIF Citizen
  • Posts: 202
  • Admiral Franklin of the McGillicuddy Highland Navy
    • View Profile
Re: What the Buoys are telling
« Reply #1730 on: August 11, 2017, 02:17:45 AM »
The halocline has all but collapsed.

Perhaps you could highlight on that ITP 95 T&S plot what you consider to be evidence for your assertion?
Had just been musing on the potential benefit of having a third profile contour plot to go with the temperature and salinity ones, namely, the water density profile. (Or could instead plot the gradient of the density.)

That should be easily derived from the information already in the other two and would show more directly where the density gradient was small i.e. 'halocline all but collapsed'.

Is that third profile contour ever plotted along with the other two?

That would be REAL nice wouldn't it.

If anyone could recommend  an app  I can download that can work with the matlab file types they provide the raw data in I wouldn't mind having a go.
Anyway Looking at :


The blue salinity 34 contour is well within swell mixing level of the surface and its only 34.7 at about 150m depth where the temp is up to 1.8 degrees.

Heres ITP 7 from 2007 for comparison. Reached Fram straight in mid September.





Here we have 33,32 even below 32 all the way to fram straight down to 100m
A layer that hasn't existed for a couple of years on the ITP record over 35 at the very bottom. Of very warm very salty water. All the early years have it. Not sure if its still there but deeper, or co-mixed now. But the 0C contour is down at 150m with lots of very cold stable above it.

I found  a salinity / temp / pressure  density tool here:
http://www.csgnetwork.com/water_density_calculator.html
A few results. 1dbar is just over 1m depth:

Salinity 34.7,  1.5C 150dbar  =1028.477g/L,   1027.769 at surface
Salinity 34.7, 1.8C 150dbar = 1028.453,   1027.747 at surface
Salinity 34, -1.5C 20dbar = 1027.456 ,   1028.081 at 150dBar
Salinity 34,  -1.8C surface = 1027.368,  20dbar = 1027.464, 150 dbar = 1028.091

A 1/1000 to 1/ 2000 difference looks pretty unstable to my uneducated eyes.


Perhaps the ITP95 DO contours tell a better signature.
They have bottom to top upwellings solidly represented for the last month.

« Last Edit: August 11, 2017, 05:51:48 AM by Hyperion »
Policy: The diversion of NZ aluminum production to build giant space-mirrors to melt the icecaps and destroy the foolish greed-worshiping cities of man. Thereby returning man to the sea, which he should never have left in the first place.
https://en.wikipedia.org/wiki/McGillicuddy_Serious_Party

Rob Dekker

  • ASIF Upper Class
  • Posts: 1002
    • View Profile
Re: What the Buoys are telling
« Reply #1731 on: August 11, 2017, 04:08:20 AM »
Thank you Victoria, for your explanation of the irradiance sensors, and the WARM buoy in general.

I have a few more comments and questions :

3) To get from sensors to PAR in W/m^2, which algorithm did you use? And would it be hard to adjust the algorithm so that it produces an estimate of full-spectrum irradiance?


The sensor inside the PAR channel has a filter in front of it that lets through all light between 400 and 700 nm. This means that we can't get a full spectrum from this kind of instrument.

That is of course true, but the PAR sensor has a 400 nm - 700 nm filter and you calculate the 'energy' flow through that in W/m^2. Since we know that 400nm - 700nm contains about 43% of the energy of the full spectrum of normal sunlight, isn't it OK to just multiply your PAR irradiance [W/m^2] by 1/0.43=2.3 to obtain at least a first-order 'full-spectrum' energy flux ?

Regarding the WARM 3 irradiance data, this remark from you was an eye-opener :

As the ice melts the buoy slips through the hole, with all the sensors becoming 3 m deeper in the water.

Brilliant ! That explains the sudden drop-off in irradiance in mid-July of both in-ice and under-ice sensors ! The sensors all slipped 3 meters down, as is also witnessed by your pressure sensors :

It's good to know that is how the WARM buoys are constructed, since WARM 6 is about to entertain the same maneuver, right ?
 
Now the only thing odd about the WARM 3 data is that extremely high irradiance for the in-ice sensors during June. That (irradiance up to 350 W/m^2) is very high when compared to WARM 6, and its very high when compared to the under-ice irradiance (of less than 10 W/m^2).

Overall, with these WARM buoys you got yourself a beautiful set of cool instruments, Victoria. Thank you for sharing the data with us.

Rob Dekker

  • ASIF Upper Class
  • Posts: 1002
    • View Profile
Re: What the Buoys are telling
« Reply #1732 on: August 11, 2017, 05:06:51 AM »
One more question, Victoria :

In the same image as the graphs for irradiance (see above) there is a graph for something labeled as "DOM(?) fluorescence" in ppb (parts per billion).

What is that exactly, and which sensor records it ?

ktonine

  • ASIF Citizen
  • Posts: 363
    • View Profile
Re: What the Buoys are telling
« Reply #1733 on: August 11, 2017, 06:07:34 AM »
One more question, Victoria :

In the same image as the graphs for irradiance (see above) there is a graph for something labeled as "DOM(?) fluorescence" in ppb (parts per billion).

What is that exactly, and which sensor records it ?

A quick Google search says that fDOM = fluorescent dissolved organic matter as opposed to cDOM which is colored dissolved organic matter. These are topics Dr Hill has written on extensively.

Rob Dekker

  • ASIF Upper Class
  • Posts: 1002
    • View Profile
Re: What the Buoys are telling
« Reply #1734 on: August 11, 2017, 06:47:40 AM »
Just when you think you have a constructive discussion going on about a genuinely interesting subject, there is always Ktonine to slap you down.

Jim Hunt

  • ASIF Governor
  • Posts: 3421
    • View Profile
    • The Arctic sea ice Great White Con
Re: What the Buoys are telling
« Reply #1735 on: August 11, 2017, 11:22:20 AM »
Just when you think you have a constructive discussion going on about a genuinely interesting subject, there is always Ktonine to slap you down.

Now, now boys. There's far too much of that sort of thing going on over at the ASIB even as we argue speak!

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

Tor Bejnar

  • ASIF Upper Class
  • Posts: 1669
    • View Profile
Re: What the Buoys are telling
« Reply #1736 on: August 11, 2017, 06:51:49 PM »
The water-ice interface once again looks (to me) like some surface freezing recently took place, and that afterwards the water level fell, or, more likely, the ice edge raised up. 

For the ice edge to rise, I think this means surface melt has to be significantly faster than bottom melt. Enlargement from Obuoy 14 camera image.
Arctic ice is healthy for children and other living things.

magnamentis

  • ASIF Upper Class
  • Posts: 1279
    • View Profile
    • Philosophy Ethics Numerology Mikrocirkulation Vaskular Therapie Gesundheit Blut Gesundheit Schmerzen Multiple Sklerose Diabetes Immunsystem Fibromyalgia Modular Mobile Computing iOS Software OSX Android Custom Rom Rooted
Re: What the Buoys are telling
« Reply #1737 on: August 11, 2017, 09:35:06 PM »
The water-ice interface once again looks (to me) like some surface freezing recently took place, and that afterwards the water level fell, or, more likely, the ice edge raised up. 

For the ice edge to rise, I think this means surface melt has to be significantly faster than bottom melt. Enlargement from Obuoy 14 camera image.

don't think so, the ice is melting from below and the edges get thinner and thinner. temps were well above zero yesterday and hover around zero for the reminder, certainly it's too warm there to build new ice from water.

the raise comes with the melting ice sitting higher in the water, well observable with ice-bergs that melted so much that the former waterline at times can be serveral meters above the water surface.

further, again looking at  bergs, one can often see how they get some mushroomy form factore, well visible once they capsize and the underwater melt being stronger than the surface melt is the very reason why they topple at all, they become top-heavy.
http://magnamentis.com
Knowledge, Understanding & Insight Are Among The Best Sources For Personal Freedom & Vitality !

oren

  • ASIF Upper Class
  • Posts: 1713
    • View Profile
Re: What the Buoys are telling
« Reply #1738 on: August 12, 2017, 07:59:38 AM »
Top melt continues.

Sterks

  • ASIF Citizen
  • Posts: 157
  • Member # 1000
    • View Profile
Re: What the Buoys are telling
« Reply #1739 on: August 12, 2017, 12:18:46 PM »
We are looking at ocean water, aren't we?
The small lift of the ice over the surface can be either because we are looking now at the natural sea level against the ice, not melt pond level. Also, ice cohesive enough can locally lift a bit due to pressure ridging.
In any case I can't see how the level can say anything about the bottom melt rate, no matter if we look at melt pond or ocean water.

Chun_Kaoriina

  • ASIF Lurker
  • Posts: 6
    • View Profile
    • my twitter
Re: What the Buoys are telling
« Reply #1740 on: August 12, 2017, 01:07:38 PM »
I think it does tell us, that there's at least some bottom melt happening (duh). I agree that this cant be melt ponds anymore (looking at satellite pics for the area). Maybe the protrusion comes from the waves? could be the wave's maximum height
it might tell us something about top vs bottom melt too though. if the former above-sea-level-part is now higher than before, that means it's part of the total mass is smaller. which is why we know top melt > bottom melt

Sterks

  • ASIF Citizen
  • Posts: 157
  • Member # 1000
    • View Profile
Re: What the Buoys are telling
« Reply #1741 on: August 12, 2017, 01:11:19 PM »
Understood, thank you

Jim Hunt

  • ASIF Governor
  • Posts: 3421
    • View Profile
    • The Arctic sea ice Great White Con
Re: What the Buoys are telling
« Reply #1742 on: August 12, 2017, 01:20:05 PM »
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Jim Hunt

  • ASIF Governor
  • Posts: 3421
    • View Profile
    • The Arctic sea ice Great White Con
Re: What the Buoys are telling
« Reply #1743 on: August 12, 2017, 01:24:58 PM »
With a hat tip to Andreas T, some further insight into the sort of thing the WARM buoys are hoping to spot?

How to find an eddy

After some quick calculations, the ocean had revealed its structure along this line: Underneath the long line of ice was a dome of much warmer water that had possibly been raised from greater depth. Such upward motion of water may bring nutrient rich water into depths where there is still enough light for phytoplankton to grow and can also drag copepods and other zooplankton up. This is why the oceanographic pattern is also of great biological interest.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Andreas T

  • ASIF Upper Class
  • Posts: 1081
    • View Profile
Re: What the Buoys are telling
« Reply #1744 on: August 12, 2017, 01:36:14 PM »
Undercutting of the ice edge is a feature of meltponds which can be seen in all buoy footage I have seen, especially later in the season, possibly linked to salinity of the water when mixing with ocean water below is occurring. I don't think ice growing out or lifting is involved, the small waves on the water surface will splash against the ice and melt it a little above the water surface.
Together with the warmer temperatures we have seen recently relative humidity has also been high. This shows that the air has not warmed locally (which would drop humidity) but has moved in from warmer areas and cooled to its dew point. If this has brought some condensation to the ice surface that would of course strengthen surface melt.

Relevant to the discussions of temperature and salinity profiles, there is a report by Polarstern on their site, which describes an eddy and its effect on those profiles. It is in the Fram strait at the moment.
https://www.awi.de/nc/en/expedition/ships/polarstern/weekly-reports-rv-polarstern/single-view/presse/woche-2-wie-man-einen-wirbel-findet.html
Jim has already linked to this as I was typing :o
It also reminded me of reading in Peter Wadham's "a farewell to ice" about a very persistent eddy he investigated in the Odden Ice tongue (when there still was one)

Jim Hunt

  • ASIF Governor
  • Posts: 3421
    • View Profile
    • The Arctic sea ice Great White Con
Re: What the Buoys are telling
« Reply #1745 on: August 12, 2017, 03:04:43 PM »
Jim has already linked to this as I was typing :o

Great minds think alike Andreas!
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Tor Bejnar

  • ASIF Upper Class
  • Posts: 1669
    • View Profile
Re: What the Buoys are telling
« Reply #1746 on: August 12, 2017, 05:09:20 PM »
Thanks, Andreas.  The tiny 'shelf' seen in the pictures being associated with wave height makes a great deal of sense. 

Years ago when I lived up north, I had salted my walkway on a 'hot' February morning.  I was looking at a stream of water flowing in a shovel-created channel (maybe 2 cm across and 1 cm deep) on top of the ice and noticed a skim of 'new' ice had formed in some places over the top of the steam.  I figured out that the salt, lowering the melting point of the ice, created a stream of 'hyper-cold' salty water, and that 'fresh' water coming in contact with this colder flowing 'substance' froze ('just like what happens in an ice cream maker').

This is what happens when 'fresh water' melted snow flows through channels toward the cold sea below (sealing the channels and maintaining the melt pond), and I'm certain happens at the surface.  I just hadn't figured out why there was a gap between the sea surface and the lip of new ice (and associated undercut of the floe)
Arctic ice is healthy for children and other living things.

Tor Bejnar

  • ASIF Upper Class
  • Posts: 1669
    • View Profile
Re: What the Buoys are telling
« Reply #1747 on: August 12, 2017, 05:23:42 PM »
Curious: what happened to the O-Buoy 14 path on the O-Buoy Overview map?  The buoy continues to provide data, at least it did at 1400 UTC (10 a.m. Eastern USA time) - and hour+ ago.  Did the batteries stop? Compare with August 10 image (above)

Edit:  the 15:01 hour camera image showed up (by 15:47 UTC)
Edit2: O-Buoy 14 was back on the Overview map (by 16:15 UTC)
« Last Edit: August 12, 2017, 06:22:18 PM by Tor Bejnar »
Arctic ice is healthy for children and other living things.

Andreas T

  • ASIF Upper Class
  • Posts: 1081
    • View Profile
Re: What the Buoys are telling
« Reply #1748 on: August 12, 2017, 05:54:16 PM »
I see the buoy track ok, could it be that Obuoy14 has somehow been deselected (there is a list on the right hand side menu which pops up when you click on the + sign)

Tor Bejnar

  • ASIF Upper Class
  • Posts: 1669
    • View Profile
Re: What the Buoys are telling
« Reply #1749 on: August 12, 2017, 06:17:43 PM »
O-Buoy 14 shows up again on the Overview map.  It wasn't there 30 minutes ago, though. (I'll put an 'edit' on my previous post.)

The battery graph updated this past hour, too!
« Last Edit: August 12, 2017, 06:27:44 PM by Tor Bejnar »
Arctic ice is healthy for children and other living things.