Author Topic: What the Buoys are telling (Read 949591 times)

uniquorn · « **Reply #2050 on:** January 28, 2021, 05:01:49 PM »

Quote from: oren on January 28, 2021, 01:58:38 PM

Great animation. While looking at it, the concept of a "Beaufort Gyre" seems more absurd than ever. Sometimes the buoys make a concerted effort to drift clockwise, but most of the time they just go every which way. And even when they do follow a pattern, it's not the same pattern every time, the directions are different.

I think there's a hint of gyre there. An overlay of nullschool wind might show whether it's all wind drift or there is also an ocean current component.

Here's the full arctic ocean version, jan2016-jan2021.
January 1st data has been removed as it gives animation errors and some other data has been removed to clean things up a bit

Quote

data <- data[which(data$Lat < 90 ),]
data <- data[which(data$Lon > -180 ),]
data <- data[which(data$Lon < 360 ),]
data <- data[which(data$drift < 0.99),]
data <- data[which(data$drift > 0),]

Obviously many more things could be improved upon. Reluctant to increase compression to reduce file size any further.

uniquorn · « **Reply #2051 on:** January 30, 2021, 02:13:45 PM »

5 years of daily iabp buoy drift and nullschool wind at 1000hPa. 2016-jan2021 11.3MB mp4 beware

Quote

ffmpeg -i buoy.avi -i wind.avi -filter_complex "
crop=w=448:h=438:x=4:y=20[c1]; [1]crop=w=448:h=438:x=0:y=0[c2]; [c2][c1]blend=all_mode='overlay':all_opacity=1[m];
[m]overlay=x=4:y=20" -crf 34 buoywind-crf34.mp4[/size]

interesting. Forum turns 0 in square brackets into bullet points

Best viewed at half speed. (four and a half minutes you'll never get back

)

uniquorn · « **Reply #2052 on:** February 02, 2021, 11:54:04 AM »

The whoi itp113 profiler is struggling with shallower water and/or a low battery voltage. It really has done a great job since September 18, 2019. Would have been great if it could have recorded more of the changes crossing the chukchi plateau though.
All temperature and salinity profiles from jan1-feb2 (click 8.4MB, using x to help show single data points)
Profile contours, drift path (off the map) and rough latest location.

Brigantine · « **Reply #2053 on:** February 13, 2021, 11:59:14 PM »

An ARGO float in the WSC north of Svalbard, which last reported in October, has woken up again!

Float ID 7900550.

Just a scratch of a halocline, and a 2-300m layer of Atlantic water still at ~2.5C.

Really pretty similar to some of the profiles from October, sans the halocline. Or rather, with the halocline being absorbed into the Atlantic layer.

uniquorn · « **Reply #2054 on:** February 14, 2021, 06:21:18 PM »

Quote from: Brigantine on February 13, 2021, 11:59:14 PM

Float ID 7900550.
Just a scratch of a halocline, and a 2-300m layer of Atlantic water still at ~2.5C.<<>>>

You probably know more than me... keeping an eye on it though

Sepp · « **Reply #2055 on:** February 15, 2021, 10:07:43 AM »

Quote from: Brigantine on February 13, 2021, 11:59:14 PM

An ARGO float in the WSC north of Svalbard, which last reported in October, has woken up again!

Float ID 7900550.

Just a scratch of a halocline, and a 2-300m layer of Atlantic water still at ~2.5C.

Really pretty similar to some of the profiles from October, sans the halocline. Or rather, with the halocline being absorbed into the Atlantic layer.

Nice visualisation! Could you give a hint how to get historical data to compare this with some years ago?

Niall Dollard · « **Reply #2056 on:** February 15, 2021, 01:33:53 PM »

Hi Sepp.

There is a wealth of detailed studies, freely available here, mostly between circa 2014 and 2016, of the Sofia Deep, north of Svalbard. It is quite a large file with the start in french and then english.

https://tel.archives-ouvertes.fr/tel-01721467/file/these_archivage_3003710o.pdf

The ocean interactions are very complex at this location. But I have attached a sample profile for winters 2014 to 2016 at approximately the same location as the float 7900550

Sepp · « **Reply #2057 on:** February 17, 2021, 10:42:48 PM »

Thank you very much.

I was actually interested in the movement of the zone of relative high Salinity/Temperature (Halocline?) upwards over the last years in general. I remember having seen it somewhere in the forum in a year-to-year comparison and it looked quite upsetting, so I suspect, I was a bit offtopic with my question here.

Anyway, thanks again (:

Brigantine · « **Reply #2058 on:** February 18, 2021, 01:35:46 AM »

Quote from: Sepp on February 15, 2021, 10:07:43 AM

Nice visualisation! Could you give a hint how to get historical data to compare this with some years ago?

I mostly just use the "preview profile" feature on this USGODAE Argo GDAC Data Browser. You can go back and look at the data from whatever year... but only when there's a float in your target region to get data from! AFAIK there weren't any that far north until the last year or two.

Occasionally download the data and run it through some equations to plot density (buoyancy). Tried to predict how the surface mixed layer would grow, but without any success. The floats seem to pop up in a different idiosyncratic pocket each new profile.

Quote from: uniquorn on February 14, 2021, 06:21:18 PM

You probably know more than me... keeping an eye on it though

Not at all! I keep an eye on what the floats are seeing in certain regions, but I'm not in any position of knowledge, and as far as the why and the what next, I'm just as confused as anyone. So I appreciate anything you have to say on it!

uniquorn · « **Reply #2059 on:** February 18, 2021, 01:03:13 PM »

Quote from: Niall Dollard on February 15, 2021, 01:33:53 PM

There is a wealth of detailed studies, freely available here, mostly between circa 2014 and 2016, of the Sofia Deep, north of Svalbard. It is quite a large file with the start in french and then english.
https://tel.archives-ouvertes.fr/tel-01721467/file/these_archivage_3003710o.pdf
The ocean interactions are very complex at this location. But I have attached a sample profile for winters 2014 to 2016 at approximately the same location as the float 7900550

Handy to have all those studies in one file.

Update on float 6903547 in the Fram Strait, Feb16 (feb6 below) A deeper cold layer on this profile.
https://fleetmonitoring.euro-argo.eu/float/6903547
@Brigantine I struggled a bit with the .nc format with the USGODAE Argo GDAC Data Browser. It's quick for previews though.

uniquorn · « **Reply #2060 on:** February 18, 2021, 03:40:55 PM »

Quote from: Sepp on February 17, 2021, 10:42:48 PM

interested in the movement of the zone of relative high Salinity/Temperature (Halocline?) upwards over the last years<<>>

argo float 3901910 made it up the WSC north Svalbard branch during aug-dec 2018. Some posts about it here

Though perhaps you are thinking about the Aug2020 Polyakov paper discussed here

uniquorn · « **Reply #2061 on:** February 22, 2021, 10:09:39 PM »

SIMB3 443910 is paired with whoi itp120 in the beaufort.

Quote

Instrument experienced a dynamic event on 09/29/2020 which caused a downward shift in the rangefinder values and failure of the temperature string.

Ice+snow appear to have thickened by 64cm to 1.716m

uniquorn · « **Reply #2062 on:** February 22, 2021, 10:27:00 PM »

SIMB3 344910 is paired with whoi itp121 in the beaufort.

Ice+snow appear to have thickened by 65cm to 2.753m

uniquorn · « **Reply #2063 on:** February 27, 2021, 02:47:14 PM »

Quote from: Brigantine on February 13, 2021, 11:59:14 PM

An ARGO float in the WSC north of Svalbard, which last reported in October, has woken up again!
Float ID 7900550.
Just a scratch of a halocline, and a 2-300m layer of Atlantic water still at ~2.5C.
Really pretty similar to some of the profiles from October, sans the halocline. Or rather, with the halocline being absorbed into the Atlantic layer.

and again on 20th, must have been under ice for a while previously. Temp at 5m depth = -0.077C, atlantic water(mixed layer?) down to ~200m

uniquorn · « **Reply #2064 on:** February 27, 2021, 06:31:19 PM »

argo 3902108 approaching the NW corner of Svalbard, 3.3C at 3m depth on feb24

argo 6903547 a little further west in the Fram, 3.36C at 2.8m depth on feb26

SimonF92 · « **Reply #2065 on:** February 27, 2021, 08:13:25 PM »

Quote from: uniquorn on February 27, 2021, 02:47:14 PM

Quote from: Brigantine on February 13, 2021, 11:59:14 PM
An ARGO float in the WSC north of Svalbard, which last reported in October, has woken up again!
Float ID 7900550.
Just a scratch of a halocline, and a 2-300m layer of Atlantic water still at ~2.5C.
Really pretty similar to some of the profiles from October, sans the halocline. Or rather, with the halocline being absorbed into the Atlantic layer.

and again on 20th, must have been under ice for a while previously. Temp at 5m depth = -0.077C, atlantic water(mixed layer?) down to ~200m

-0.07 at that depth and location in winter seems pretty warm to me? Just goes to show how bad halocline disturbance by storms can be for the ice

uniquorn · « **Reply #2066 on:** March 05, 2021, 12:13:18 PM »

SIMB3 443910 is paired with whoi itp120 in the beaufort.
Ice+snow appear to have thickened during the freezing season by 72cm from 1.12m to 1.786m
Location: 2021 63.75089 -148.2591 74.9978

SIMB3 441910 is paired with whoi itp121 in the beaufort.
Ice+snow appear to have thickened by 67cm from 2.1m to 2.771m
Location: 2021 63.75089 -150.4194 73.3404

Both buoy locations are just visible on yesterday's iwsviewer image here
This doesn't work for me using firefox but does with chrome

Buoy location is roughly centre of image

added images enhanced from polarview jp2. Tempting to think the bright dot is the buoy.

uniquorn · « **Reply #2067 on:** March 10, 2021, 11:41:47 AM »

Quote from: uniquorn on February 27, 2021, 06:31:19 PM

argo 6903547 a little further west in the Fram, 3.36C at 2.8m depth on feb26

argo 6903547 may be too far west to take the North Svalbard branch of the WSC.

1.4C at ~3.8m depth on mar8 (charts

uniquorn · « **Reply #2068 on:** March 12, 2021, 11:24:58 AM »

whoi itp120 update. That drop in salinity in the middle of the Canada Basin shown in the profile contours appears to be real. Sometimes they are due to the profiler not being able to move. Odd that there is no temperature change.

itp120 profile contours

itp120 drift path

Temperature and salinity, feb1-mar12 (click)

OffTheGrid · « **Reply #2069 on:** March 12, 2021, 07:39:11 PM »

If these Buoys are indeed mounted in solid floes then there's questions about how this resonant drift speed phenomenon has continued all winter. The supplied for both 121 and 120 are too course for me to comment on the periodicity. But obviously there's quasi monthly, 4-5 day, and about twice daily components.
If they are in solid floes rather than having melted out, then it must be a rotating dancing slush puddle, ekman turbine mixing process.
There is no way that a football sized crawler going up and down a cable once a day could cause such periodicity in drift speed variations.
Quite surprised that mass balance Buoys could be showing such thickening. I thought they hadn't been providing the data because the Buoys were free floating in withering slush Ice. The blob of thicker ice off the CAA in September that they and the colocated imbs were placed in the edges of has certainly withered.

How long has the IMB data been available. Every time I have looked its just been "site under construction"

uniquorn · « **Reply #2070 on:** March 12, 2021, 09:48:13 PM »

itp120 and 121 drift jan1-mar12
There are some probable inertial oscillations, clearly visible during jan9-19. They would be roughly twice daily. The cryosphere innovation links are up thread.

no one noticed my figures were incorrect last week. Thickening since deployment has been
210cm to 278cm 68cm
112cm to 181cm 69cm
Not much to write home about but 'rotating dancing slush puddle' - probably not.
'Periodicity' might reveal something, data is attached for further analysis.

overlaid drift chart.

static drift path for low vol users, jan1-mar12

drift animation, jan1-mar12

csv file drift data.

uniquorn · « **Reply #2071 on:** April 09, 2021, 06:02:01 PM »

Latest temperature profiles from 3 buoys on the Greenland Sea/Barents Sea border. Note the time and depth scales are very different. https://fleetmonitoring.euro-argo.eu/float/6903565.

That warming is perhaps too deep to be due to shallow sun angle and less ice, could possibly be incoming Atlantic water.

uniquorn · « **Reply #2072 on:** April 10, 2021, 12:17:36 AM »

A closer look at argo 6903565 recent temps in the Barents
edit, missed the latest one..
Looking back further though this could be part of a cycle or possibly wind driven. Check feb19-22 with https://earth.nullschool.net/#2021/02/22/2200Z/wind/surface/level/overlay=temp/orthographic=-47.95,91.77,993

oren · « **Reply #2073 on:** April 10, 2021, 01:56:32 PM »

Thanks for these updates uniquorn.

uniquorn · « **Reply #2074 on:** April 10, 2021, 10:05:32 PM »

argo 6903547 reporting 2.894C at near surface on apr7

argo 3902112 at 3.416 a little further south on apr6

uniquorn · « **Reply #2075 on:** April 14, 2021, 12:18:06 PM »

argo float6903558 surfaced on apr10, reporting 2.142C at 15m. It doesn't look like there was ice in the area. I wonder why it didn't gather data nearer the surface.

https://argo.ucsd.edu/how-do-floats-work/telecommunications-systems/

Quote

Data transmission systems

As the float ascends, a series of pressure, temperature, salinity and other measurements are made and stored on board the float. These are transmitted to satellites when the float reaches the surface. For floats using high speed communications with more bandwidth capabilities, measurements are taken frequently, often up to every 2db, resulting in several hundred measurements per profile. For floats using Argos, a series of 200 measurements of pressure, temperature, and salinity are taken.

For a shrinking percentage of floats in the Argo array (less than 25%), the data are transmitted from the ocean surface via the Système Argos location and data transmission system. The data transmission rates are such that to guarantee error free data reception and location in all weather conditions the float must spend between 6 and 12 hrs at the surface. Positions are accurate to ~100m depending on the number of satellites within range and the geometry of their distribution.

The majority of floats in the Argo array now use the Global Positioning System (GPS) to establish float positions and use Iridium to transmit their data. When newer float models began developing in 2010, Iridium was chosen as the new telecommunications service because it allows more detailed profiles to be transmitted in a shorter time period at the surface and it allows two-way communication with the float to change the float’s mission if desired. Since 2013, the majority of floats being deployed used Iridium communications and will slowly replace the Argos floats as they reach the end of their life.

uniquorn · « **Reply #2076 on:** April 24, 2021, 05:14:20 PM »

IABP buoy drift update. Mar1-apr24, click twice for full res and movement

Easterly mosaic buoys reach the Fram
A lot of new buoys around the sidex area.

Tor Bejnar · « **Reply #2077 on:** April 24, 2021, 06:26:09 PM »

From my casual look at wind and pressure maps others have posted, the buoys recent movement doesn't surprised me. "All roads lead to Rome," as they say, with 'Rome' spelled "F R A M".

At least for now, anyway.

Next week or next month will surely tell a somewhat different story. (For the sake of the ice I hope, anyway.)

uniquorn · « **Reply #2078 on:** April 25, 2021, 01:26:08 PM »

The Fram funnel might be getting larger these days.

Here taking a closer look at the Sidex buoys. Jennifer Hutchings mentioned an event in the update
No gap in the data so that pause on the left is due to a lead opening up.

The wayward buoy is 300434064052460 which is only reporting data intermittently

Jim Hunt · « **Reply #2079 on:** April 25, 2021, 07:30:41 PM »

Quote from: uniquorn on April 25, 2021, 01:26:08 PM

Here taking a closer look at the Sidex buoys.

Do we need a dedicated SIDEx thread?

uniquorn · « **Reply #2080 on:** April 30, 2021, 02:03:41 PM »

With 5 other interested people, probably not

I was curious what a recent transect of the chukchi plateau (5m and 6m temps) would look like.
Temps peaking twice as it crosses the shelf break. I thought a closer look might reveal some places where 6m were warmer than 5 ~~but it seems not.~~

subtracting 6m from 5m did reveal some small diffs, haven't checked if all the dates match. There are ~11000. There are 28 less 6metre temps, every 6min, so diff could be nearly 3hrs out by the end.

animation over bathy might be interesting.

uniquorn · « **Reply #2081 on:** May 03, 2021, 11:57:23 PM »

quick and dirty sidex buoys drift update (km/s)

uniquorn · « **Reply #2082 on:** May 07, 2021, 12:14:25 AM »

Mosaic buoys roughly following the shelf break. One getting left behind in the shallows.
apr23-may5

SimonF92 · « **Reply #2083 on:** May 07, 2021, 05:34:32 PM »

Active and non-bugged IABP buoys, 07-May-21

uniquorn · « **Reply #2084 on:** May 11, 2021, 02:01:22 PM »

iabp daily drift update, apr12-may11

uniquorn · « **Reply #2085 on:** May 11, 2021, 03:19:58 PM »

A closer look at the Laptev/CAB and a very close look at 204762. The ice already mobile enough to show inertial oscillations or tidal movement (which may be stronger in this location) or a combination of both

uniquorn · « **Reply #2086 on:** May 24, 2021, 12:19:41 AM »

6 cryosphere innovation buoys in the Beaufort. Possible ridging on Sidex#2

uniquorn · « **Reply #2087 on:** June 01, 2021, 04:35:56 PM »

The IABP site has been down for a while but we have some buoy data up to may30 thanks to the sterling efforts of Wendy and Ignatius.

HapHazard · « **Reply #2088 on:** June 01, 2021, 06:38:46 PM »

the Atlantic side has a 1 track mind

uniquorn · « **Reply #2089 on:** June 01, 2021, 08:00:38 PM »

The buoy in the FJL-SV gap (68816640) is one of the last remaining Mosaic Pbuoys in the Arctic Ocean, 2020P236. Meereisportal appear to have stopped providing data on May4 but Wendy's latest IABP data only has a gap from may10-20 (the straight line is interpolated)
Maybe we will get a polarview image to identify the floe before it melts.

Quote

300234068816640;2021;00;00;150.0000;150.0000;82.05100;27.19310;-999;-2.58;-999
300234068816640;2021;01;00;150.0417;150.0420;82.04930;27.20020;-999;-2.56;-999
300234068816640;2021;02;00;150.0833;150.0830;82.04660;27.20420;-999;-2.59;-999
300234068816640;2021;03;00;150.1250;150.1250;82.04290;27.20560;-999;-2.51;-999
300234068816640;2021;04;00;150.1667;150.1670;82.03820;27.19990;-999;-2.61;-999
300234068816640;2021;05;00;150.2083;150.2080;82.03370;27.18640;-999;-2.48;-999
300234068816640;2021;06;00;150.2500;150.2500;82.03000;27.16800;-999;-2.49;-999
300234068816640;2021;07;00;150.2917;150.2920;82.02620;27.14140;-999;-2.50;-999
300234068816640;2021;08;00;150.3333;150.3330;82.02320;27.11140;-999;-2.43;-999
300234068816640;2021;09;00;150.3750;150.3750;82.02120;27.08340;-999;-2.53;-999
300234068816640;2021;10;00;150.4167;150.4170;82.02010;27.05990;-999;-2.45;-999
300234068816640;2021;11;00;150.4583;150.4580;82.01960;27.04310;-999;-2.37;-999
300234068816640;2021;12;00;150.5000;150.5000;82.01940;27.03380;-999;-2.41;-999
300234068816640;2021;13;00;150.5417;150.5420;82.01850;27.02680;-999;-2.39;-999
300234068816640;2021;14;00;150.5833;150.5830;82.01700;27.01970;-999;-2.42;-999
300234068816640;2021;15;00;150.6250;150.6250;82.01440;27.01390;-999;-2.36;-999
300234068816640;2021;16;00;150.6667;150.6670;82.01100;27.00930;-999;-2.34;-999
300234068816640;2021;17;00;150.7083;150.7080;82.00760;27.00420;-999;-2.39;-999
300234068816640;2021;18;00;150.7500;150.7500;82.00420;27.00250;-999;-2.32;-999
300234068816640;2021;19;00;150.7917;150.7920;82.00040;27.00630;-999;-2.24;-999
300234068816640;2021;20;00;150.8333;150.8330;81.99660;27.00280;-999;-2.22;-999
300234068816640;2021;21;00;150.8750;150.8750;81.99330;26.98150;-999;-2.26;-999
300234068816640;2021;22;00;150.9167;150.9170;81.99030;26.95470;-999;-2.16;-999
300234068816640;2021;23;00;150.9583;150.9580;81.98790;26.92780;-999;-2.18;-999

Looks kind of lonely

uniquorn · « **Reply #2090 on:** June 02, 2021, 01:48:11 PM »

SIMB3 SIDEx 2021#3 in the Beaufort showing signs of warming at ice surface. Maybe thinned a bit.

Two temperature profile charts, the top one to show near surface air temperature, the bottom highlights ice temperature changes during summer. Please note the temperature limits. Hopefully the snow layer is in the correct position.

Bruce Steele · « **Reply #2091 on:** June 03, 2021, 09:15:14 PM »

Surface water at Red Dog Dock starting to heat up. 35F for awhile today

https://tidesandcurrents.noaa.gov/physocean.html?id=9491094

uniquorn · « **Reply #2092 on:** June 03, 2021, 11:36:30 PM »

Thanks Bruce Steele, red dog went a little higher. whoi itp121 hovering over the edge of the chukchi plateau

co located simb3 441910 still flatline, no sign of melt yet

uniquorn · « **Reply #2093 on:** June 04, 2021, 10:54:03 PM »

More on whoi itp121. Some turbulence as depth decreases from 3800m to 1000m in 10km along the steeper sections of the shelf break. 2 of the last 4 profiles are incomplete.

uniquorn · « **Reply #2094 on:** June 07, 2021, 08:59:42 PM »

Argo float 3902108 popped up north of Svalbard in between floes to give us an update. -1.5C down to 15m, dropping to just over -1.8C down to 53m then back up to 1.5C at 100m
Depth at 81N 10.34E is ~1300m

Drift pressure is 1000dbar. Guessing they can they detect ocean depth or it got dragged over 60km of ocean floor at 500m-600m to reach its current location.
https://argo.ucsd.edu/how-do-floats-work/

Quote

Floats equipped with an Ice Sensing Algorithm evaluate the temperature data they measure while approaching to the surface. If the temperature is below a predetermined threshold, indicating that sea ice is expected above, the ascending trajectory is aborted thus preventing the float from hitting the ice from below. The float then proceeds to start another cycle and tries to surface again after 10 days. The process repeats until the float senses it is safe to surface, when it transmits all the profiles taken under ice, which are stored internally on the float.

Never seen this before https://www.ocean-ops.org/board?t=oceanops choose projection UPS north

uniquorn · « **Reply #2095 on:** June 18, 2021, 11:14:13 AM »

New glider design aims to expand access to ocean science
https://www.whoi.edu/oceanus/feature/ocean-glider-open-source/

Quote

In 2018, close to midnight on Martha's Vineyard, engineer John Reine couldn’t sleep. His hands, plunged into a watering trough on his family’s farm, were dunking a homemade version of a common, data-collecting submersible known as a glider—praying it would work. If it did, Reine would have proven to himself that one of ocean science’s most versatile tools would be simple enough for most engineers to build from scratch. At 1 a.m., the glider, powered by hydraulics from a CamelBak water pouch squeezed by Reine, began to rise and fall at his command.

“It was enough for me to say, ‘Okay, these aren’t that hard to build from scratch,’” says Reine, a lead electronics engineer for the Ocean Observatories Initiative (OOI) at WHOI.

Invented in the 1960s, ocean gliders have become a linchpin for oceanographic data collection. As their name and torpedo-shape suggest, they glide up and down through different layers of the ocean, using a payload of sensors to measure water temperature, salinity, and marine chemistry. These days, they’ve been crucial for filling important data gaps at ocean depths where stationary observation moorings can’t reach.

But Reine says there’s a problem: Right now, there’s only a few places where you can purchase and service gliders or their parts—for WHOI, a conglomerate known as Teledyne Technologies. That’s created a bottleneck for scientists trying to get the instruments out to sea quickly.

Jim Hunt · « **Reply #2096 on:** June 18, 2021, 11:46:13 AM »

Quote from: uniquorn on June 18, 2021, 11:14:13 AM

New glider design aims to expand access to ocean science

Thanks for the heads up. See also:

https://github.com/mightyferrite/OpenGlider

and:

https://github.com/johnreine/seaflightglider

Bruce Steele · « **Reply #2097 on:** June 19, 2021, 02:19:35 AM »

ITP 121 has a photo sensor with its Sami device. The PAR has jumped over the last ten days. This indicates melt ponding at 76 north lat. PAR usually spikes with meltponds then drops back down as when the meltponds melt through and the ice gets more opaque .

Glen Koehler · « **Reply #2098 on:** June 19, 2021, 06:50:17 PM »

In my world PAR = Photosynthetically Active Radiation. Not clear to me why those particular wavelengths (400 -700nm) would be of special importance to ASI, so not clear what PAR means in this context. No PAR entry in the ASIF glossary.

uniquorn · « **Reply #2099 on:** June 19, 2021, 07:51:10 PM »

Not my area of expertise but any buoy data is welcome. My understanding is that as ice gets thinner we get more PAR and more algae or phytoplankton which can also reduce albedo in a feedback loop, but I think the funding interest is probably for future seasonal fishing possibilities

https://www.frontiersin.org/articles/10.3389/fmars.2020.00183/full

Quote

The transmission of ultraviolet (UVR) and photosynthetically available radiation (PAR) through sea ice is a key factor controlling under-ice phytoplankton growth in seasonally ice-covered waters. The increase toward sufficient light levels for positive net photosynthesis occurs concurrently with the sea ice melt progression in late spring when ice surface conditions shift from a relatively homogeneous high-albedo snow cover to a less reflective mosaic of bare ice and melt ponds. Here, we present a detailed dataset on the spatial and temporal progression of transmitted UVR and PAR in relation to changing quantities of snow, sea ice and melt ponds. Data were collected with a remotely operated vehicle (ROV) during the GreenEdge landfast sea ice campaign in June–July 2016 in southwestern Baffin Bay. Over the course of melt progression, there was a 10-fold increase in spatially averaged UVR and PAR transmission through the sea ice cover, reaching a maximum transmission of 31% for PAR, 7% for UVB, and 26% for UVA radiation. The depth under the sea ice experiencing spatial variability in light levels due to the influence of surface heterogeneity in snow, white ice and melt pond distributions increased from 7 ± 4 to 20 ± 6 m over our study. Phytoplankton drifting in under-ice surface waters were thus exposed to variations in PAR availability of up to 43%, highlighting the importance to account for spatial heterogeneity in light transmission through melting sea ice. Consequently, we demonstrate that spatial averages of PAR transmission provided more representative light availability estimates to explain under-ice bloom progression relative to single point irradiance measurements during the sea ice melt season. Encouragingly, the strong dichotomy between white ice and melt pond PAR transmittance and surface albedo permitted a very good estimate of spatially averaged light transmission from drone imagery of the surface and point transmittance measurements beneath different ice surface types.

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