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Messages - uniquorn

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1
Arctic sea ice / Re: The 2020/2021 freezing season
« on: Today at 11:29:34 AM »
iabp buoy204760-764 update, surface temperatures, oct11-28

2
Arctic sea ice / Re: The 2020/2021 freezing season
« on: Today at 12:59:19 AM »
CS2SMOS difference between oct22 and oct25 with average uncertainty of those 2 dates.

Not quite ready to let go of a relationship to bathymetry yet so here is the overlay. It reminds me of something noted in august

added polarview, oct26. Still looks like an active eddy.

3
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 27, 2020, 10:40:05 PM »
Some of the data included with CryoSat2-Soil Moisture and Ocean Salinity merged sea ice thickness netCDF (oct18-24).

I currently have plot size set to 220 so the map will later crop to 500 pxl width; the scale bar will fit under it if set to 25 with tick format %0f with size 6 font. The map is stereographic at -45º 90º with outer edge 65º.
Will work towards this set up.

5
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 27, 2020, 12:13:23 PM »
Big waves are again forecasted for the siberian side. Strong winds are usual at this time of the year, but the fetch should be zero or almost zero. Here, winds are blowing over open water. As a consequences, waves of 4 - 6 meters with a period of 8 - 10 seconds for Chukchi and Kara sea... A good washing again.
Hard for ice to form in seas with 4 meter waves. How deep does the mixing of water occur in such seas?

An essay from Peter Wadhams 2003  How Does Arctic Sea Ice Form and Decay?
Quote
How ice forms in rough water
If the initial ice formation occurs in rough water, for instance at the extreme ice edge in rough seas such as the Greenland or Bering Seas, then the high energy and turbulence in the wave field maintains the new ice as a dense suspension of frazil, rather than forming nilas. This suspension undergoes cyclic compression because of the particle orbits in the wave field, and during the compression phase the crystals can freeze together to form small coherent cakes of slush which grow larger by accretion from the frazil ice and more solid through continued freezing between the crystals. This becomes known as pancake ice because collisions between the cakes pump frazil ice suspension onto the edges of the cakes, then the water drains away to leave a raised rim of ice which gives each cake the appearance of a pancake. At the ice edge the pancakes are only a few cm in diameter, but they gradually grow in diameter and thickness with increasing distance from the ice edge, until they may reach 3-5 m diameter and 50-70 cm thickness. The surrounding frazil continues to grow and supply material to the growing pancakes.

At greater distances inside the ice edge, where the wave field is calmed, the pancakes may begin to freeze together in groups and eventually coalesce to form first large floes, then finally a continuous sheet of first-year ice known as consolidated pancake ice. Such ice has a different bottom morphology from normal sea ice. The pancakes at the time of consolidation are jumbled together and rafted over one another, and freeze together in this way with the frazil acting as "glue". The result is a very rough, jagged bottom, with rafted cakes doubling or tripling the normal ice thickness, and with the edges of pancakes protruding upwards to give a surface topography resembling a "stony field".

This open access article from Nature covers winter storms in much greater detail, describing both positive and negative effects on ice growth.

Winter storms accelerate the demise of sea ice in the Atlantic sector of the Arctic Ocean
Robert M. Graham, Polona Itkin, […]Mats A. Granskog    25 June 2019
Quote
Abstract
A large retreat of sea-ice in the ‘stormy’ Atlantic Sector of the Arctic Ocean has become evident through a series of record minima for the winter maximum sea-ice extent since 2015. Results from the Norwegian young sea ICE (N-ICE2015) expedition, a five-month-long (Jan-Jun) drifting ice station in first and second year pack-ice north of Svalbard, showcase how sea-ice in this region is frequently affected by passing winter storms. Here we synthesise the interdisciplinary N-ICE2015 dataset, including independent observations of the atmosphere, snow, sea-ice, ocean, and ecosystem. We build upon recent results and illustrate the different mechanisms through which winter storms impact the coupled Arctic sea-ice system. These short-lived and episodic synoptic-scale events transport pulses of heat and moisture into the Arctic, which temporarily reduce radiative cooling and henceforth ice growth. Cumulative snowfall from each sequential storm deepens the snow pack and insulates the sea-ice, further inhibiting ice growth throughout the remaining winter season. Strong winds fracture the ice cover, enhance ocean-ice-atmosphere heat fluxes, and make the ice more susceptible to lateral melt. In conclusion, the legacy of Arctic winter storms for sea-ice and the ice-associated ecosystem in the Atlantic Sector lasts far beyond their short lifespan.

<>

Winter storms enhance ocean mixing, heat fluxes, and ice melt
Sea ice dampens energy transfers between the atmosphere and ocean, and therefore the Arctic Ocean is traditionally considered to be energetically ‘quiet’ with weak turbulent mixing58. However, strong winds during the N-ICE2015 winter storms enhanced ice drift speeds54 (Figs 3a and 5a), which increased ocean-ice velocity shear59. These processes were found to generate mixing in the upper ocean, and led to increased transfer of ocean heat towards the ice59,60 (Fig. 5c–e). Observed winter ocean-ice heat fluxes typically more than tripled from 2 W m−2 to 7 W m−2 during storm periods (Fig. 5c, Methods), further impeding ice growth and in several cases initiating bottom melt59,60 (Fig. 3b).

Ocean mixing is particularly important in many regions of the Arctic Ocean because warm water of Atlantic origin is located below cold and fresh Polar Surface Water61. Along the continental slope north of Svalbard, warm Atlantic Water (>2 °C) is found close to the surface (Figs 1, 5e). Vertical mixing thus generates enhanced ocean heat fluxes. The magnitude of this heat flux is dependent on the mixing rate, as well as the depth and temperature of the warm water. During the N-ICE2015 winter drift over the deep Nansen Basin, Modified Atlantic Water (>0 °C) was found at approximately 100 m depth62. Under calm conditions in the deep Nansen Basin, Meyer et al.60 observed ocean heat fluxes at the pycnocline of approximately 3 W m−2 (Fig. S1). However, during storm periods, wind-driven mixing almost doubled the pycnocline heat fluxes to 5.5 W m−2 (Methods, Fig. S4a). These enhanced ocean heat fluxes are relatively small in comparison to changes in the atmospheric surface energy budget during storms37 and were insufficient to induce ice bottom melt, but nevertheless acted to further suppress ice growth (Figs 2e and 5c). Previous work using autonomous buoy measurements have inferred enhanced ice-ocean heat fluxes during winter storms in the Beaufort Sea25. It is therefore expected that these conditions in the Nansen Basin are representative of large areas of the central Arctic Ocean.

Accepted that the water has to be cold enough to form frazil ice.

Thanks for the post above A-team. I'll check out the error anomaly. That area seems already identified as possible out of range results.

6
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 26, 2020, 11:46:04 PM »
cs2smos thickness difference, oct23-25.
Guessing that blue spot must be bathy related.

7
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: October 26, 2020, 09:49:55 PM »
atlantic side oct25-26
CAB extent

8
Developers Corner / Re: Test space
« on: October 26, 2020, 09:34:16 PM »
with v103 overlay at 60%. Interesting effect with amsr2 moving over the stationary repeated missing frames.

9
Developers Corner / Re: Test space
« on: October 26, 2020, 01:40:43 PM »
a quick look at ascat, some missing days, best viewed slow --

11
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 25, 2020, 07:22:05 PM »
amsr2-awi-v103, atlantic side oct24-25. Sea ice crossing the shelf close to SZ.

12
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 25, 2020, 03:28:53 PM »
Thanks SimonF92. Animation scope widened to include the 2 newer buoys 204763 and 204764
Looking forward to your animations

13
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 25, 2020, 02:50:27 PM »
IABP buoy drift and surface temperature update.(11MB)

closer look at iabp204761 and 204762 in the Laptev (3.5MB)
click

14
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 25, 2020, 12:46:16 PM »
IABP buoy drift and surface temperature update. A steady drift along the line from Chukchi to Fram since oct6 until recently. My buoy list needs updating since it doesn't appear to include 204672 above. (12MB is a bit large) edit: updating this updated below

Unrelated but also interesting is the amount of heat escaping from the Nth Greenland Coast. https://go.nasa.gov/2HxW0GH

amsr2 awi v103, oct14-24
click for animations.

polarview S1B

15
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 25, 2020, 11:16:46 AM »
Here is the Oct 23rd situation. Panoply makes a quite decent no-click map out of GHRSST data with a little help from AMSR2_AWI, OsiSaf and Gimp.
20201023000000-OSPO-L4_GHRSST-SSTfnd-Geo_Polar_Blended_Night-GLOB-v02.0-fv01.0.nc
An excellent combination.

IABP raw data is available in the format shown below. The map shows the locations and the data can be looked up using the table

iabp204672 204762 is shown below. The default scales are large but you can create your own chart from the data.

16
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 24, 2020, 03:10:02 PM »
A closer look at refreeze not keeping up with dispersion in the Beaufort yesterday, amsr2 awi v103 oct12-23. Winds were not strong, just a little warmer.

Also moving the conversation about whoi itp121 from the melting season to this thread. Latest temperature/salinity profiles and drift path.
Temperature at 50m still high at over 2C.

itp121 shares a floe with ice mass balance buoy www.cryosphereinnovation.com/441910 currently maintaining thickness at ~2m.

17
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: October 24, 2020, 12:04:42 AM »
atlantic side oct22-23
wipneus' CAB extent

18
Arctic sea ice / Re: The caa-greenland mega crack
« on: October 23, 2020, 10:53:11 PM »
nth greenland oct16-23    https://go.nasa.gov/3jqDayn
Not that much open water, some of the darker coastal areas are fog over refreeze.

19
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: October 23, 2020, 04:18:24 PM »
amsr2, awi dev v103 overlaid onto mercator 0m ocean temperature and salinity, sep4-oct22  (8MB)
Combined these two ani's from the freezing season thread to make it easier to compare daily changes.

20
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 23, 2020, 03:40:46 PM »
Mercator's take on SST's.
amsr2, awi dev v103 overlaid onto mercator 0m ocean temperature, sep4-oct22  (7MB)
Ok, from your animation is it correct to say all the regions susceptible to warming from Atlantic Waters are already covered by ice or about to be covered? (exception Barents and Kara but we know those two seas are already lost to climate change)
It seems to me the anomalously warm Laptev and ESS areas are basically over the shallow shelf, which will have a record heat release (consistent with the record heat income from GAAC and the season in general). So no Atlantic warmth here to speak about.

The Laptev sea extent beyond the shelf (and so the heat anomaly, by the way). Intrusion of Atlantic waters are discernible on the salinity maps of the mercator. (P.S. : And acknoledging that the heat and salinity extent beyond the Laptev into the central bassin, even under the sea ice).
Yes, SST is more useful if we also show SSS
amsr2, awi dev v103 overlaid at 75% transparent onto mercator 0m ocean salinity, sep4-oct22  (7MB)
mercator label is just visible.
edit: It has often been proposed that the Atlantic waters would meet the Pacific incoming at some point. The delay in refreeze and perhaps some mixing from recent strong winds would seem to make that prospect more likely (according to the model). The Siberian shelf and the Chukchi plateau help to prevent it. (Shown on the 92m salinity map upthread)

21
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 23, 2020, 02:35:23 PM »
Mercator's take on SST's.
amsr2, awi dev v103 overlaid onto mercator 0m ocean temperature, sep4-oct22  (7MB)

22
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 21, 2020, 11:57:41 AM »
NSIDC ease-grid ice sea age update. The nearest clear day I found on Worldview for comparison in the Beaufort was oct8. https://go.nasa.gov/2IITyxk
click for animation.
edit: 2000-2020 animation here

23
Arctic sea ice / Re: The Rammb Slider Thread
« on: October 21, 2020, 11:23:10 AM »
Nice. Makes me wonder if heat loss would have been visible like that in previous years with a drier atmosphere.

24
Developers Corner / Re: Test space
« on: October 20, 2020, 10:59:42 PM »
IBCAO_v4_200m-sliced

25
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 20, 2020, 09:05:31 PM »
The 3-day forecast is finally going below freezing on the Russian side of the Arctic, although still far above normal: https://climatereanalyzer.org/wx/fcst_outlook/?dm_id=arc-lea&nday=3-day

Sometimes we have to be careful looking at temperature maps in areas of open water as the models will always forecast higher temperatures whilst that open water is there. As far as I understand it, if ice did indeed grow in some of that open water area, the models will show slightly colder temperatures than first predicted. As it happens though, it seems difficult at this point too see much refreeze from the main pack but hopefully we will see more evidence of coastal ice forming with winds blowing in from the landmasses.
There are some signs of light coastal refreeze along the esas. AMSR2 (awi v103) struggling to detect it consistently oct9-19, polarview S1 showing more detail on oct19.

26
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 20, 2020, 02:20:05 PM »
https://go.nasa.gov/3m5uQpn  oct15-20 with AWI AMSR2 v103 inset. The north greenland gap still recovering from the summer, sea ice still lifting off Ellesmere Island. Some Nares export.

27
Arctic sea ice / Re: The 2020 melting season
« on: October 20, 2020, 12:44:04 PM »
a closer look at itp121 drift, oct18-19

28
Arctic sea ice / Re: The 2020 melting season
« on: October 20, 2020, 11:10:45 AM »
A closer look at itp121 drift path. Small signs of inertial oscillation or tidal movement. It shares a floe with SIMB441910 (https://www.cryosphereinnovation.com/441910), thickness 210cm at deployment. (click for more data)

forum software behaving strangely today.

29
Arctic sea ice / Re: The 2020 melting season
« on: October 20, 2020, 12:50:10 AM »
itp121 has hardly moved. Temperature at 50m remains relatively high. Both temperature and salinity suggesting turbulence. Day 264-293.

30
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 19, 2020, 11:55:12 PM »
For what is worth (not much, admittedly), but the surface analysis of GFS (the GDAS) did not show a significant drop for SST during the week-end. <>
Raw surface temperatures and drift from iabp buoys over the last 5 days. Drift speed is the coloured path with scale at top left, temperature as text label. (Buoys in ice should be reporting ice surface temperatures. NA means they do not report surface temperature, some may be faulty.)
Click twice for full res. Large file.

31
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: October 18, 2020, 09:36:43 PM »
CAB extent update.
Atlantic side, oct8-18
added updated pixel count

32
Arctic sea ice / Re: The caa-greenland mega crack
« on: October 18, 2020, 12:35:06 AM »
CAA north coastal ice still restless. click for movement and full res.
https://go.nasa.gov/3lW02qZ

33
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: October 18, 2020, 12:17:30 AM »
CAB extent update.
Atlantic side, oct7-17
updated below

34
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: October 17, 2020, 12:55:53 AM »
updated below

35
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: October 16, 2020, 11:45:21 PM »
Just a hint of nares export over the last few days
https://go.nasa.gov/2H8Tu9A

36
Arctic sea ice / Re: What the Buoys are telling
« on: October 16, 2020, 09:07:22 PM »
something like splitting seasons at day265. Working on that

37
Developers Corner / Re: Test space
« on: October 16, 2020, 03:41:39 PM »
wake timing a bit quick -removed

38
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: October 15, 2020, 11:06:53 PM »
CAB extent update

39
Arctic sea ice / Re: What the Buoys are telling
« on: October 15, 2020, 10:48:20 PM »
A closer look at the Atlantic side temperatures at 80m depth. Max temp has been capped at -0.8C to show detail along the transpolar drift line. This means that some data is not shown fully at the Yermak plateau. I plan to look at that in more detail later.

40
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: October 15, 2020, 12:42:21 AM »
2020 again setting a new boundary for CAB refreeze (wipneus' CAB)
updated below

41
Arctic sea ice / Re: The 2020 melting season
« on: October 14, 2020, 11:12:31 PM »
@Oren, the static chart is a valuable addition to the analysis.

csv data as text file attached. conversion from day numbers/year may need checking.

42
Arctic sea ice / Re: The 2020 melting season
« on: October 14, 2020, 11:01:49 PM »
Beaufort 50m temperatures from whoi itp buoys, 2006-2020
edit: adjusted buoy sizes so newer year overlay is easier to identify
edit2: mp4 is smaller

43
Arctic sea ice / Re: What the Buoys are telling
« on: October 14, 2020, 10:12:41 PM »
overview of 50m temperature from whoi itp buoys, 2006-2020.

44
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 14, 2020, 03:29:34 PM »
Definitely some more refreeze outside the Lena delta.
Yes. Today may be the last day to check using corrected reflectance. Sea temperatures 50km from the coast were still just a touch cooler than the Lena river. Low cloud and fog a bit cooler.
Rainbow1 palette on viirs brightness temperature.
https://go.nasa.gov/374tZkp

45
Arctic sea ice / Re: MOSAiC news
« on: October 14, 2020, 01:28:33 PM »
T78 and T81 update.
T81 taking a long time to cool(thicken). There are some deployment notes for T78 but nothing for T81.

46
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: October 14, 2020, 01:06:31 PM »
Tidally Forced Lee Waves Drive Turbulent Mixing Along the Arctic Ocean Margins
Ilker Fer, Zoé Koenig, Igor E. Kozlov, Marek Ostrowski, Tom P. Rippeth,, Laurie Padman, Anthony Bosse, Eivind Kolås
First published: 06 August 2020

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020GL088083

Quote
Abstract

In the Arctic Ocean, limited measurements indicate that the strongest mixing below the atmospherically forced surface mixed layer occurs where tidal currents are strong. However, mechanisms of energy conversion from tides to turbulence and the overall contribution of tidally driven mixing to Arctic Ocean state are poorly understood. We present measurements from the shelf north of Svalbard that show abrupt isopycnal vertical displacements of 10–50 m and intense dissipation associated with cross‐isobath diurnal tidal currents of ∼0.15 m s−1. Energy from the barotropic tide accumulated in a trapped baroclinic lee wave during maximum downslope flow and was released around slack water. During a 6‐hr turbulent event, high‐frequency internal waves were present, the full 300‐m depth water column became turbulent, dissipation rates increased by a factor of 100, and turbulent heat flux averaged 15 W m−2 compared with the background rate of 1 W m−2.

47
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 13, 2020, 11:31:10 PM »
It's time to go to night vision using worldview terra modis viirs brightness temperature band 15 (night or day) https://go.nasa.gov/2FpoLVd
Today's image showing the effect of wind driven drift on the Atlantic front (awi amsr2 v103 from yesterday inset)

Quote
The VIIRS Brightness Temperature, Band I5 Night layer is the brightness temperature, measured in Kelvin (K), calculated from the top-of-the-atmosphere radiances. It does not provide an accurate temperature of either clouds nor the land surface, but it does show relative temperature differences which can be used to distinguish features both in clouds and over clear land. It can be used to distinguish land, sea ice, and open water over the polar regions during winter (in cloudless areas).

The VIIRS Brightness Temperature layer is calculated from VIIRS Calibrated Radiances (VNP02) and is available from the joint NASA/NOAA Suomi National Polar orbiting Partnership (Suomi NPP) satellite. The sensor resolution is 375m, the imagery resolution is 250m, and the temporal resolution is daily.

Only one Polarview S1B of the area today.

It's also worth looking at relatively cloud free sea ice north of the CAA today. High winds are forecast for this area too over the next couple of days.      https://go.nasa.gov/3dAMzSN

48
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 12, 2020, 11:33:01 AM »
Thanks for the SMOS post. As we suspected, all that MYI exported to the Beaufort tail has nearly melted out, and will give no resilience against next year's melting season.
It effectively amounts to open water except energy to refreeze further area is closer to zero.
For practical purposes Beaufort sea is free of MYI facing the refreeze season

It will be interesting to see what the NSIDC ice age update looks like. Here is a polarview S1A of the stalwart MYI floe at the centre of the amsr2 inset (awi v103). It's looking somewhat rounded, so has probably not had an easy time during the melting season.   ~300km2, maybe it will show up on cryosat2 if it doesn't drift too quickly.
Quote
CryoSat-2 will achieve improved spatial resolution of 250 m in the along-track direction using the Synthetic Aperture technique.
https://earth.esa.int/web/guest/missions/esa-operational-eo-missions/cryosat/overview

49
Arctic sea ice / Re: The 2020/2021 freezing season
« on: October 11, 2020, 11:02:23 PM »
Just a hint of coastal refreeze in parts of the Lena delta on worldview. Quite a change from sep23. (click for ani)

polarview, oct10

Oddly enough, further north it still looks like melt season.

50
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: October 11, 2020, 08:23:00 PM »
No data for 2012 but 2020 is about to test the boundary set by 2018 for slow refreeze in the CAB.

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