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Messages - uniquorn

Pages: [1] 2 3 ... 14
1
Arctic sea ice / Re: MOSAiC news
« on: Today at 02:28:42 PM »
We missed the crossover into atlantification waters somewhere behind the salinity legend.
Nobody is looking.
100m and 75m salinity starts rising mid february, PS was travelling NW at the time.
50m salinity joins them later in feb, Will have to check 20m sometime.
Not all sensors are active


Mosaic Obuoys

2
Arctic sea ice / Re: MOSAiC news
« on: April 06, 2020, 09:54:09 PM »
An estimate of sea ice thickness based on data from mosaic Thermistor Buoys , mar1-apr6 with a lot of help from SimonF92. We have also estimated snow thickness though identifying it accurately has proved problematic.
Full details of the methods attempted can be found here Comments on the methods or initial analysis of other mosaic buoy data are most welcome on that thread (please read it first).
click twice for full resolution

3
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: April 06, 2020, 09:38:37 PM »
kane basin arch, mar19-apr6   https://go.nasa.gov/3dUa8FP

4
Arctic sea ice / Re: MOSAiC news
« on: April 06, 2020, 01:58:45 PM »

5
Arctic sea ice / Re: Tides
« on: April 06, 2020, 11:48:30 AM »
<>Ghanges in gravity cause changes in pressure, which causes the water column to expand and contract. Changes in atmospheric pressure also cause changes in pressure within the water column, causing the water column to expand and contract. Hence the two phenomena are linked, and they are also of a similar magnitude.<>
A bold claim which should be easy to verify with a volume vs time chart or a scientific paper. A quick search didn't find one. Nevertheless, that search did lead me to the video attached, which is similarly challenging. Thank you.



Quote
Although each drop of water on Earth is indeed pulled by the moon's gravity, the effect isn't noticeable on a molecular level since the Earth's inward pull is overpowering.

The key, however, is that ocean water covers about 71% of Earth's surface and is connected as one liquid body. This allows the small force on each water molecule to collectively add up to "a pretty decent increase in water pressure," Perez-Giz says.

Molecules of water near Earth's poles are pulled mostly straight down toward the planet's center of gravity (near its core), and the molecules closest to the moon (at Earth's equator) experience the strongest pull toward the moon. Water molecules that are farthest from the moon, meanwhile, feel the weakest gravitational acceleration.

Since water molecules can easily move and bump into one another, these countless tiny nudges add up and "squeeze" seawater away from the poles. This global water pressure works against Earth's gravity to form two bulges: the high tides.

"The ocean isn't being lifted or stretched," Perez-Giz says. "The ocean is bulging along the Earth-moon line in the same way that a blister or pimple will bulge up if you start to squeeze it from the side."
https://www.nsf.gov/od/oia/activities/aaasfellows/bios/perez-giz.pdf

6
Looking at thickness change colours and incorporating some bathy (scale appears to be wrong). ctffr

7
Arctic sea ice / Re: MOSAiC news
« on: April 05, 2020, 11:19:27 AM »
PS doesn't appear to have frozen back in to the 'floe'. Bow radar is still rotating.
Note the temporary ridge in the middle of the refrozen lead.

8
Arctic sea ice / Re: Tides
« on: April 03, 2020, 12:04:51 PM »
Quote
The coastal oceans are forced by the deep water waves as a boundary condition, because the shallow areas have little mass and are not much impacted by the gravitation of the planetary objects. This boundary condition moves water on and off the shallow areas
Thank you Andreas. The tidal discussion was prompted by comments relating to the Fram Strait but I'm curious whether tidal forces affect sea ice in the area north of FJL and Svalbard where the depth rapidly increases from ~200m to over 3000m into the Nansen basin. I expect that 200m isn't considered shallow, but can your explanation be extrapolated to apply to that depth?
I'm aware that the ice drift is wind driven but the low concentration area doesn't move with the ice.
uni-hamburg amsr2uhh, Svalbard and FJL, mar27-apr2
rammb animation of the same area here

9
Arctic sea ice / Re: Tides
« on: April 02, 2020, 11:08:47 PM »
I'd like to refer you to uniqorn's "where does the water come from" comment above. Even the best and most valuable of members, that have been providing the rest of us with a constant and positive input (such as yourself) can be totally off when it comes to such basic scientific facts as what a pressure wave actually is.

That is why I dare! Because none of us knows all, but some of us have a better basic understanding of physics than others. This basic understanding can of course lead you into the briar patch, but when something jars against it, I not only dare to respond, but I do.

So silly claims, such as that the phases of the moon can effect Fram export, will be bashed by me now and in the future.
When the tide goes up, where does the water at the bottom come from?
Same happens when changes in atmospheric pressure cause corresponding changes in sea surface (appr. 1 cm per millibar, see here). Whithin the Northern Atlantic and the Arctic, differences in atmospheric pressure from one place to another can easily exceed 50 mbar, leading to a difference in sea level of half a metre. Again, this is due to expansion and contraction of the water column.

Please explain how this is relevant.

Quote
Relation between sea level and barometric pressure determined from altimeter data and model simulations
Philippe Gaspar Space Oceanography Division, Collecte Localisation Satellites, Toulouse, France Rui M. Ponte Atmospheric and Environmental Research, Inc., Cambridge, Massachusetts
Abstract.
The relation between sea level and barometric pressure and, specially, the validity of the inverted barometer (IB) approximation is examined over the global oceans, using nearly 2 years of TOPEX-POSEIDON altimeter measurements. Both crossover differences and collinear differences between consecutive cycles are utilized in this study. Linear regressions between barometric pressure and sea level time series yield coefficients between 0.8 and 1 cm/mbar poleward of 20 ø and as low as 0.5 cm/mbar in the equatorial regions. Such deviations from the IB value of 1 cm/mbar can be due to the presence of data errors or to correlations between pressure and adjusted sea level (i.e., sea level corrected for IB effect). A simple error model for the pressure fields and a number of sensitivity tests are used to evaluate the changes in the regression coefficient possibly induced by data errors (pressure errors, altimeter measurements errors, and radial orbit errors). The combined (root-mean-square) effect of the different errors amounts to 0.8 mm/mbar poleward of 20 ø and 1.8 mm/mbar within 20 ø of the equator, in general smaller than the observed deviations from the IB value. Regression coefficients thus imply a correlation between adjusted sea level and pressure. Results from a shallow-water, global ocean model forced by realistic wind and pressure fields corroborate this finding. The model is able to explain the observed coefficients, within measurement errors, with wind- driven effects being most important in accounting for differences from the simple IB model. Pressure-forced dynamical signals cause maximum deviations of only 1 mm/mbar. The analyses point to the general validity of the IB approximation over the deep oceans but also highlight the complex relation between sea level and barometric pressure resulting from correlations between various sea level signals.

This might have been a better riposte

10
Easier to see slow down in thickening, probably due to temp, with a 'taller' scale
btw SF, Nice emulation ctr

11
The 2 remaining cryosphereinnovation simb buoys are in broad agreement with our numbers. Snow depth perhaps more stable.
piomas indicating our results should be a touch thicker

12
Will look at that in a bit. First draft of the ani. My initial impression is that it's a shame to lose the path detail by using only 1frame/day. How about we use all the ts data but replicate the thicknesses.
Note that none of the buoys are over 2m thick using this method.  ctr
I have a feeling they are all going to experience sudden melt at this drift rate.

adjusted a few things ctffr
and added est snow thickness, though I can't do 2 colours at a time.

13
Arctic sea ice / Re: Tides
« on: April 01, 2020, 01:29:40 PM »
When the tide goes up, where does the water at the bottom come from?

14
Arctic sea ice / Re: The 2020 melting season
« on: March 31, 2020, 12:27:24 PM »
ascat day60-89 comparison (or closest available day), 2010-2020. First year ice distinguishable by location and darkness. click to run
Maybe Niall will measure the movement :)

15
Alcohol shouldn't be a problem. We make a lot of plum and fig wine but only one gallon of grape. Though it will be weaker if the sugar runs out. Anything that's undrinkable gets turned into eau de vie. If that's undrinkable it makes a good handwash. No shortage of vinegar either, some if it cider.
We'll go with chestnuts rather than acorns.

16
Arctic sea ice / Re: The 2020 melting season
« on: March 30, 2020, 06:04:18 PM »
historical perspective
It's difficult to compress a long time series into a small enough file size so this is 6.5MB for ascat fram export 2010-2020. The present episode doesn't look like the worst thing that has happened (yet).
I can remove this after 47hrs if it causes problems to low bandwidth users.

Also large, but not auto downloaded is worldview, terra modis, closest non cloudy day to mar29, 2000-2020. Medium contrast has been applied to highlight leads.
Some years look worse, 2010 looks bad in a different way. click to run

uni-hamburg amsr2uhh, caa and nth greenland, 2012-2018 can be found here

17
Arctic sea ice / Re: MOSAiC news
« on: March 30, 2020, 01:47:17 PM »
S1B from mar28 and mar30. PS getting sheared
85.3776N 13.1756 @ 08:40

18
Arctic sea ice / Re: MOSAiC news
« on: March 30, 2020, 01:47:43 AM »
Overview of Pbuoys (not P88) click to run, twice for full res - ctrtffr

19
Arctic sea ice / Re: MOSAiC news
« on: March 29, 2020, 09:19:25 PM »
There's a newish Rbuoy if anyone wants to analyse albedo

20
Arctic sea ice / Re: The 2020 melting season
« on: March 29, 2020, 08:42:49 PM »
nothing out of the ordinary
One thing that is different, or that I haven't seen before, is the large leads that have developed since feb15 making their way around north greenland so early in the season. With >80km/h winds forecast on apr1 we are likely to see them open up more.
Kaleschke SIC leads, oct1-mar29

21
Thinking about those rough charts, it would be easier to compare them if they all started on the same date. I think the shallow gradient was during the warm spell in October, some of the Tbuoy's data don't start till late oct/nov. Of course, if the ice is thin, it thickens quicker.

22
Rough charts based on the data above. Some different curves.
Note that the heat120 method appears to shift the air-snow and snow-ice thermistor no.s upwards, possibly due to heat rising. I haven't corrected for this. Even so, that doesn't explain 0 or negative starting position unless data was sent before (or during) buoy installation. hey ho, it's an estimate.

23
Estimated thermistor numbers based on last entry in heat120 files (chart attached, cffr)
buoy   Th(snow)   Th(ice)
T56   24   35
T58   18   34
T62   40   51
T63   18   32
T64   24   47
T65   12   35
T66   42   49
T68   34   46
T70   32   42
T72   28   36

T69   25   35


24
Arctic sea ice / Re: MOSAiC news
« on: March 28, 2020, 09:13:30 PM »
Latest S1B (cffr) PS is white dot roughly centre, on the rift

25
Arctic sea ice / Re: The 2020 melting season
« on: March 27, 2020, 11:37:51 AM »
Following up on amsr2 ice concentration in the Beaufort. The present conditions perhaps alter or amplify surface reflections that are not normally visible since the sensor is picking up features that move with the ice, probably ridges. (Temporarily providing us with SIC ridges as opposed to SIC leads) Heavy contrast has been applied to the right hand image.

The second animation shows a more persistent low concentration area in the Laptev. We will find out soon enough if that is real or also an artifact of 'conditions'

unihamburg-amsr2uhh, beaufort, mar14-26 and ess/laptev, mar10-26

26
Arctic sea ice / Re: The 2020 melting season
« on: March 26, 2020, 12:44:59 PM »
I suspect that it is due to heavy cloud cover and/or other atmospheric conditions at this time of year. There was a similar discussion last year (and some before that)
Here is uni-hamburg mar31 2019 for comparison. It disappeared a few days later.
It is also visible on Aluminium's 2019 link above.

27
Arctic sea ice / Re: The 2020 melting season
« on: March 26, 2020, 11:03:20 AM »
There is evidence that the heat is there in the Beaufort from whoi itp114 but at 30m depth, with little visible mixing, it is unlikely to have a large impact at the moment. sep20-mar26
Salinity is steadily rising at 5m depth but that could be down to brine release from ice formation. 
click for full resolution. Day numbers at bottom of charts

28
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: March 25, 2020, 06:10:19 PM »
Looking back, a few small sections of younger ice have broken off since the 16th.
https://go.nasa.gov/2JhllSO

29
Looking only at T64 where the chart shows 3 clear drops in estimated thickness. The temperature ani doesn't show any bottom melt events. There are, however, some higher air temperatures that flatten the curve that may occur at roughly the same time as the 3drops.
Not exactly a bug but perhaps an error in the method.
Some thermistors are recording persistently higher temperatures. Perhaps there was a problem during calibration
Was using Spyder but jupyter charts are good


Still need to see a time series of the stdev(10rows) charts to see it they are messing about during temperature rises

30
Arctic sea ice / Re: The 2020 melting season
« on: March 24, 2020, 12:05:12 PM »
An overview of sea ice movement as seen by ascat, jan1-mar23
The amsr2 low concentration area in/around the Beaufort correlates quite well with the darker area on ascat but may also be related to the recent heavy cloud cover.

31
Arctic sea ice / Re: MOSAiC news
« on: March 23, 2020, 12:00:16 PM »
radar update. The ice to the north west looking stronger during that episode.

32
Arctic sea ice / Re: The 2020 melting season
« on: March 22, 2020, 08:43:02 PM »
That makes it a long time with very little Beaufort gyre movement
osi-saf, sep21-mar19

whoi itp112 drift track (deployed sep2019)

33
Arctic sea ice / Re: The 2020 melting season
« on: March 22, 2020, 10:05:15 AM »
A large area of the Chukchi Sea looking lightly frozen yesterday. https://go.nasa.gov/3a96hSQ
click for full resolution

34
Arctic sea ice / Re: The 2020 melting season
« on: March 21, 2020, 08:35:25 AM »
Kaleschke SIC leads, Fram funnel, mar10-21.
Worldview Terra Modis , Svalbard-FJL gap, mar10-20   https://go.nasa.gov/3bcw5O7
click to run

35
T69 had a trauma of some kind as noted upthread. The other drops don't show up on reply#9 animation showing bottom thickening so are probably related to the method used to detect the nearest snow/ice thermistor.
I think the 'warm snap' around feb20 may be the cause.
10 rows perhaps too short - it might be easy to edit such well documented code.... :)

36
ESS-4S, 72.77N 161.30 is visible again. https://go.nasa.gov/3a59ov2

37
Comparison of the new code (thickness_and_snow_as_timeseries.py) with the basic method. Pretty close agreement on ice thickness. We have no way of verifying snow depth but looking at other buoys may show us if we are on the right track

added yesterday's S1 of the area
nearest coords, roughly middle of the crop
2020-03-18T07:00:12,86.704520,12.369056
2020-03-18T09:00:13,86.696373,12.381268

38
Arctic sea ice / Re: The 2020 melting season
« on: March 19, 2020, 12:40:53 AM »
uni-hamburg amsr2-uhh, bering, mar10-17
added wipneus regional extent, bering, mar17

39
T56 method comparison
eyeballing the numbers Therm-snow/ice=30 for the spreadsheet method
Spreadsheet method is less complicated, std dev+ is more mathematically justifiable
Is the difference down to snow depth?

Quote
Nag to the 17: This is probably a once in a decade opportunity to use the mosaic project to gather almost unprecedented near real time arctic data. Perhaps you are content to sit back and watch a model. Maybe a view from a satellite. Maybe just wait for someone else to do it. But why? There are over 70 active buoys in the arctic today(Mar18). Why aren't we analysing them?? If we are. Why aren't we sharing??

40
testing temperature chart with SimonF92 generated provisional thickness estimate
temporary post as it is large

41
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: March 17, 2020, 09:14:08 PM »
update on the low concentration ice north of greenland using Kaleschke SIC leads. ctr

42
Arctic sea ice / Re: MOSAiC news
« on: March 17, 2020, 08:17:00 PM »
Very large lead opened up on bow radar this morning

43
Yes, R. I had to 'learn' it to hack macid's original code. Taking on python as well is a bit much.
I had a look at T64, the southernmost Tbuoy to check the ice is still thickening (at around -2°C)
Therm139 to Therm141, so ~4cm (at the bottom) over 16days.

44
I plotted the standard-deviation of temperature over a 10-hour period for (most recent data) for T56.
<>
Hopefully we are not talking to cross-purposes at the moment!
That looks a lot more robust than my method. Do you mean 10 rows? 1 every 6hrs.
I think we are aiming at the same thing, only the presentation will be different. I plan to use the thermistor numbers to show thickness on the drift animation
drift update, click to run. (might have less time than I thought)
removed-will update later

45
Arctic sea ice / Re: The 2019/2020 freezing season
« on: March 14, 2020, 06:21:34 PM »
Quote
This article states that the Barents Sea has become cooler
An interesting article, do you think it refers to surface temperature or an average over depth? It says temperatures but not which.

46
Arctic sea ice / Re: The 2019/2020 freezing season
« on: March 14, 2020, 11:07:13 AM »
It's a bit too cloudy to tell but there doesn't appear to be much sign of refreeze yet on the open leads east of Wrangel Island.
Chukchi Sea, https://go.nasa.gov/3aMQDfY (contrast),mar14, uni-hamburg amsr2-uhh, feb13 inset.
click for full resolution

47
Arctic sea ice / Re: MOSAiC news
« on: March 12, 2020, 06:05:45 PM »
A closer shear, probably still active. Drift speed from p207 at 0300 quite high at ~1km/hr

48
Developers Corner / Re: Test space
« on: March 12, 2020, 12:27:04 AM »
Testing mosaic iabp buoys over kaleschke sic leads. A bit rough
No enhancement on sic leads, just scaling. Gimp gave a colour error when saving part2. Had to do it in 2 parts, png too big I think. -removed

49
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: March 11, 2020, 05:36:00 PM »
Full moon march 9th. A tiny chip off the west side
https://col.st/uJMHJ  mar9-10

50
Arctic sea ice / Re: MOSAiC news
« on: March 05, 2020, 08:43:07 PM »
Less than 2km distance. PS at the bottom of the scale marker. KD is the white dot casting the radar shadow to the right.

A wider view, https://go.nasa.gov/2TJSpHR  cffr

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