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Messages - uniquorn

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1
Arctic sea ice / Re: The 2020/2021 freezing season
« on: Today at 09:07:12 PM »
So basically we have thicker ice on the Pacific side and thinner ice on the Atlantic side this year compared to last.  Overall, there does not appear to be a big difference.
Concur.
Overall, the damage to the refreeze has already been done.  We are now one month past the solstice, and the energy budget is rapidly moving away from building thick ice.<>

The energy budget in the west spitsbergen current north east of Kvitoya is melting ice at the moment, shown here by a rammb animation (https://col.st/jkgLd), jan 20-21, 8.4MB. Some northerly winds are forecast in a couple of days, perhaps  the open water will close up a bit if the ice is thick enough on the CAB side.
If JayW is around perhaps he can confirm if this is also showing SST mixing

amsr2-uhh, atlantic side, jan1-20
polar view of part of the 'surface feature' area, jan16, 17 and 20. (10MB)


Quote
Kvitøya (English: "White Island") is an island in the Svalbard archipelago in the Arctic Ocean, with an area of 682 square kilometres (263 sq mi). It is the easternmost part of the Kingdom of Norway. The closest Russian Arctic possession, Victoria Island, lies only 62 kilometres (39 mi) to the east of Kvitøya.

The island is almost completely covered by Kvitøyjøkulen, an ice cap with an area of 705 square kilometres (272 sq mi) with a classical, hourglass-shaped dome, which has given it its name. The few ice-free land areas are each only a few square kilometres large and very barren and rocky, the largest being Andréeneset on the southwest corner of the island. Kvitøya is a part of the Nordaust-Svalbard Nature Reserve.

2
Developers Corner / Re: Test space
« on: January 18, 2021, 10:11:57 PM »
ascat large 2020334-2021017
a bit too large - removed

3
Arctic sea ice / Re: The 2020/2021 freezing season
« on: January 18, 2021, 09:40:41 PM »
How bad is the front in the CAB vs other years? It looks atrocious, it also looks like there was just a major surface melt event on the FYI that has migrated into the CAB as the MYI has exported through FRAM...

Not sure about major surface melt but there is some surface change. There are a couple of mosaic buoys recording ice surface temperature north of Svalbard. P156 and P157

amsr2-uhh, Atlantic side, jan17, 2013-2021

added SMOS/SMAP, Atlantic side, dec1-jan17. Almost certainly not surface melt.

4
Arctic sea ice / Re: The 2020/2021 freezing season
« on: January 18, 2021, 10:28:42 AM »
A closer look at surface features detected by amsr2-uhh, atlantic side, dec1-jan17. Ascat inset for drift comparison. Some correlation recently with the FYI/SYI white band discussed up thread.

5
Arctic sea ice / Re: The 2020/2021 freezing season
« on: January 17, 2021, 02:14:17 PM »
Following up on the West Spitsbergen current, unfortunately the 2 argo floats in the current north east of Svalbard are now inactive. Here are the latest temperature and salinity charts for the 3 nearest floats to the west of Svalbard (from south to north)
SST is 4.8C close to the southern tip of Svalbard dropping to 3.4C further north.

Kolås, E. and Fer, I.: Hydrography, transport and mixing of the West Spitsbergen Current: the Svalbard Branch in summer 2015, Ocean Sci., 14, 1603–1618, https://doi.org/10.5194/os-14-1603-2018, 2018.
https://os.copernicus.org/articles/14/1603/2018/
Quote
Abstract

Measurements of ocean currents, stratification and microstructure were made in August 2015, northwest of Svalbard, downstream of the Atlantic inflow in Fram Strait in the Arctic Ocean. Observations in three sections are used to characterize the evolution of the West Spitsbergen Current (WSC) along a 170 km downstream distance. Two alternative calculations imply 1.5 to 2 Sv (1 Sv = 106 m3 s−1) is routed to recirculation and Yermak branch in Fram Strait, whereas 0.6 to 1.3 Sv is carried by the Svalbard branch. The WSC cools at a rate of 0.20 ∘C per 100 km, with associated bulk heat loss per along-path meter of (1.1−1.4)×107
 W m−1, corresponding to a surface heat loss of 380–550 W m−2. The measured turbulent heat flux is too small to account for this cooling rate. Estimates using a plausible range of parameters suggest that the contribution of diffusion by eddies could be limited to one half of the observed heat loss. In addition to shear-driven mixing beneath the WSC core, we observe energetic convective mixing of an unstable bottom boundary layer on the slope, driven by Ekman advection of buoyant water across the slope. The estimated lateral buoyancy flux is O(10−8) W kg−1, sufficient to maintain a large fraction of the observed dissipation rates, and corresponds to a heat flux of approximately 40 W m−2. We conclude that – at least in summer – convectively driven bottom mixing followed by the detachment of the mixed fluid and its transfer into the ocean interior can lead to substantial cooling and freshening of the WSC.

AMSR2-UHH north of FJL struggling with weather related ice surface changes more than usual this year.

6
Arctic sea ice / Re: The 2020/2021 freezing season
« on: January 16, 2021, 06:20:09 PM »
Looking at old ice drift and thickness using a rough overlay of cs2smos onto ascat interferometry,  oct22-jan11
thickness scale is a guide due to overlay

Daylight over the Bering Sea  https://go.nasa.gov/38PbLnu

7
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: January 13, 2021, 08:54:09 PM »
Thanks Paolo. I found 4 scales with the same palette a bit confusing so I tried 3 different ones. The first is 0m-500m to show the outline shape, then 450m-2000m and 1950m-4500m. The overlap is to cut down on white space between the different palettes.
Possible transparency issue with the second palette

Ill add one more image to the collection which might add some reasoning behind the standard deviation image. This one features more contour lines. The gradient along the glacier edge being so steep would probably raise the STD. Contours said more to me than colours in the end.

And a close up. Now I will leave you in peace :)

8
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: January 13, 2021, 10:51:38 AM »
A larger version of Ice Velocity from Images Pairs for an overview. Apologies for the fast speed, it's the only way I know how to compress a slow 53MB gif down to 2.1MB. For analysis, best to download it and view frame by frame. (or better, download the original .png files, the ani is half size, cropped)
jul2018-dec2020
The images differ in size by a few pixels so the ani jumps around a bit

I'm quite new to panoply so the third image should be treated with some caution. It focuses on a smaller area from 0-160m. Some of the settings are included in the capture.
x,y coordinate scaling may not be quite right
STD x,y velocity probably not so interesting.

9
Antarctica / Re: Pine Island Glacier (PIG) Calving and Discussion
« on: January 12, 2021, 03:44:14 PM »
PIG Along-Flow, Across-Flow ice speed and Ice Velocity from Images Pairs since may2018
http://www.cpom.ucl.ac.uk/csopr/iv/index.php?glacier_number=3
Quote
Hogg, A., A. Shepherd, N. Gourmelen (2015) A first look at the performance of Sentinel-1 over the West Antarctic Ice Sheet, FRINGE 2015, Frascati, Italy, 23-27 March 2015.

All best viewed at half speed.

10
Arctic sea ice / Re: The 2020/2021 freezing season
« on: January 12, 2021, 12:26:13 PM »
amsr2-uhh comparison of 2021 with 2016 again, jan5-11, mercator surface temps inset for 2021. The warm West Spitzbergen current clearly winning at the moment.
Polarview S1B of the area north east of Svalbard this morning (UTC)
gnrt bathy of the same area. The round indent in the ice edge in 2021 sits over the turbulent waters above the entry (or exit) to the Yermak plateau dip

edit:Those indents look like they are more to do with the shelf break than the Yermak when overlaid.

11
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: January 11, 2021, 08:41:13 PM »
Still some tidal movement in the Robeson Channel, https://go.nasa.gov/3siankW  jan2-10
rammb JPSS, band I4, jan2-11

12
Arctic sea ice / Re: The caa-greenland mega crack
« on: January 11, 2021, 06:48:59 PM »
Quote
Any idea where this black (4m) section in the Lincoln arrived from
neXtSIM models it as there all summer but I think regulars in the Nares thread would probably disagree, as does CS2SMOS, oct22-jan8 (click 5MB)
Quite a few large old MYI floes did enter the Nares though and there are still some in the Lincoln Sea.

13
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: January 10, 2021, 05:04:39 PM »
A look at CMEMS mixed layer depth model from Mercator
Quote
The Operational Mercator global ocean analysis and forecast system at 1/12 degree is providing 10 days of 3D global ocean forecasts updated daily. The time series start on January 1st, 2016 and is aggregated in time in order to reach a two full year’s time series sliding window. This product includes daily and monthly mean files of temperature, salinity, currents, sea level, mixed layer depth and ice parameters from the top to the bottom over the global ocean. It also includes hourly mean surface fields for sea level height, temperature and currents. The global ocean output files are displayed with a 1/12 degree horizontal resolution with regular longitude/latitude equirectangular projection. 50 vertical levels are ranging from 0 to 5500 meters. This product also delivers a special dataset for surface current which also includes wave and tidal drift called SMOC (Surface merged Ocean Current).


https://en.wikipedia.org/wiki/Mixed_layer
Quote
Oceanic mixed layer

Importance of the mixed layer
The mixed layer plays an important role in the physical climate. Because the specific heat of ocean water is much larger than that of air, the top 2.5 m of the ocean holds as much heat as the entire atmosphere above it. Thus the heat required to change a mixed layer of 2.5 m by 1 °C would be sufficient to raise the temperature of the atmosphere by 10 °C. The depth of the mixed layer is thus very important for determining the temperature range in oceanic and coastal regions. In addition, the heat stored within the oceanic mixed layer provides a source for heat that drives global variability such as El Niño.

The mixed layer is also important as its depth determines the average level of light seen by marine organisms. In very deep mixed layers, the tiny marine plants known as phytoplankton are unable to get enough light to maintain their metabolism. The deepening of the mixed layer in the wintertime in the North Atlantic is therefore associated with a strong decrease in surface chlorophyll a. However, this deep mixing also replenishes near-surface nutrient stocks. Thus when the mixed layer becomes shallow in the spring, and light levels increase, there is often a concomitant increase of phytoplankton biomass, known as the "spring bloom".

Oceanic mixed layer formation
There are three primary sources of energy for driving turbulent mixing within the open-ocean mixed layer. The first is the ocean waves, which act in two ways. The first is the generation of turbulence near the ocean surface, which acts to stir light water downwards.[1] Although this process injects a great deal of energy into the upper few meters, most of it dissipates relatively rapidly.[2] If ocean currents vary with depth, waves can interact with them to drive the process known as Langmuir circulation, large eddies that stir down to depths of tens of meters.[3][4] The second is wind-driven currents, which create layers in which there are velocity shears. When these shears reach sufficient magnitude, they can eat into stratified fluid. This process is often described and modelled as an example of Kelvin-Helmholtz instability, though other processes may play a role as well. Finally, if cooling, addition of brine from freezing sea ice, or evaporation at the surface causes the surface density to increase, convection will occur. The deepest mixed layers (exceeding 2000 m in regions such as the Labrador Sea) are formed through this final process, which is a form of Rayleigh–Taylor instability. Early models of the mixed layer such as those of Mellor and Durbin included the final two processes. In coastal zones, large velocities due to tides may also play an important role in establishing the mixed layer.

The mixed layer is characterized by being nearly uniform in properties such as temperature and salinity throughout the layer. Velocities, however, may exhibit significant shears within the mixed layer. The bottom of the mixed layer is characterized by a gradient, where the water properties change. Oceanographers use various definitions of the number to use as the mixed layer depth at any given time, based on making measurements of physical properties of the water. Often, an abrupt temperature change called a thermocline occurs to mark the bottom of the mixed layer; sometimes there may be an abrupt salinity change called a halocline that occurs as well. The combined influence of temperature and salinity changes results in an abrupt density change, or pycnocline. Additionally, sharp gradients in nutrients (nutricline) and oxygen (oxycline) and a maximum in chlorophyll concentration are often co-located with the base of the seasonal mixed layer.

Oceanic mixed layer depth determination
The depth of the mixed layer is often determined by hydrography—making measurements of water properties. Two criteria often used to determine the mixed layer depth are temperature and sigma-t (density) change from a reference value (usually the surface measurement). The temperature criterion used in Levitus[5] (1982) defines the mixed layer as the depth at which the temperature change from the surface temperature is 0.5 °C. The sigma-t (density) criterion used in Levitus[5] uses the depth at which a change from the surface sigma-t of 0.125 has occurred. Neither criterion implies that active mixing is occurring to the mixed layer depth at all times. Rather, the mixed layer depth estimated from hydrography is a measure of the depth to which mixing occurs over the course of a few weeks.

The mixed layer depth is in fact greater in winter than summer in each hemisphere. During the summer increased solar heating of the surface water leads to more stable density stratification, reducing the penetration of wind-driven mixing. Because seawater is most dense just before it freezes, wintertime cooling over the ocean always reduces stable stratification, allowing a deeper penetration of wind-driven turbulence but also generating turbulence that can penetrate to great depths.

Palette colours chosen to highlight 10m-190m. West Spitzbergen current and other areas are deeper at times.

14
Arctic sea ice / Re: The caa-greenland mega crack
« on: January 10, 2021, 04:49:14 PM »
Crack update. Small lift off from CAA coast, NE Ellesmere ice is holding on.

15
Arctic sea ice / Re: The caa-greenland mega crack
« on: January 10, 2021, 04:44:09 PM »
Following up a bit late on the neXtSIM crack disappearance on Dec8 between 00h and 01h. Their response was quick.
The Dec8 problem appears to be resolved.
different palette, black near Lincoln Sea is allegedly over 4m by this model

16
Arctic sea ice / Re: The 2020/2021 freezing season
« on: January 10, 2021, 01:50:45 PM »
<Even the sea surface temp anomalies far north, and adjacent to the ice is "warm." >
Bering Sea ice perhaps reacting to that 'warmth' and persistent northerlies by building up an ice front rather than an ice edge. Could be cloud interference causing lower concentration further north though.
amsr2-uhh, bering, dec20-jan9 (click for movement)
https://go.nasa.gov/3orir0B  jan9

17
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: January 09, 2021, 05:21:19 PM »
Kara Sea.
Compilation of AWI v103, SMOS and Mercator salinity at 34m, oct28-jan8.
Some interference in the Barents on SMOS. Some small colour changes in compilation so the scales are a rough guide

AMSR2 3.125 data from Wipneus. Kara not quite reaching the dip of 2017 yet.

18
The forum / Re: Forum Decorum
« on: January 06, 2021, 01:15:23 AM »
ASIF info centre Jan6

19
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: January 06, 2021, 12:37:36 AM »
jan4-5

20
Arctic sea ice / Re: What the Buoys are telling
« on: January 05, 2021, 12:46:37 PM »
drift track and ~6m-200m temperature and salinity profile contours for selected whoi itp's. The criteria for selection was that the buoys should drift close to or within the BGOS buoy moorings (white circles) and have a reasonably long profile. Some fail quickly. Note that there are a couple of scale changes early on and that often the drift track is longer than the profiler battery life (or other reason for failure). So, as nearly always, this is just a very rough historical guide over a small area in the Beaufort from 2006-2021
White can often be interpreted as warmer than top of the scale (off the chart) but may also be due to missing data. For itp121 white means off the chart. Found a newer version of itp5 temp.

21
Arctic sea ice / Re: The 2020/2021 freezing season
« on: January 04, 2021, 09:08:54 PM »
Comparison of whoi itp120 and 121 7m-200m temperature profiles. Small location inset.

For an older comparison, itp85 was deployed in 2014 with the profile ending in sep2 2015 so about 2/3 along the profile is roughly where itp120 is today and close to where itp121 was shortly after deployment.

22
Arctic sea ice / Re: The 2020/2021 freezing season
« on: January 04, 2021, 11:50:07 AM »
Quote
It might be related to this. The heat seems to upwell in the same general area. ...

I probably shouldn't have posted those two together. I don't think that paper relates to upwelling. It is more about warming of the Pacific layer which currently remains trapped between the 'freshwater layer' and the Atlantic layer. According to the Arctic Monitoring and Assessment Program that layer has a residence time of ~10years.

Quote
<strange, if not local, that a layer like that would slide along just under the top 25m of cold near-surface water.>

It seems to be generally accepted that ocean layers can be at quite different temperatures without mixing if there is a large enough difference in salinity. That paper shows the increase in both temperature and area, though there must be a fair amount of interpolation based on scarce data.

Does it affect freezing/thickening? We are fortunate to have a cryosphereinnovation.com ice mass balance buoy co-located with whoi itp120. A great opportunity to study thickening as the buoys travel over the warmest area of the Pacific layer.

The ice thickness chart looks odd. The buoy is a 4m long tube. I think that it must have had a short melting experience (or some other trauma) and slipped further down the bore hole.

Further reading from https://advances.sciencemag.org/content/4/8/eaat6773
Quote
ACCUMULATION OF HEAT
Halocline ventilation

The source of the increased halocline heat content can be understood by first considering how the BG halocline is ventilated. The northern Chukchi Sea (NCS) region exerts major influence on the interior structure of the halocline; here, water masses with the salinity range of the warm halocline outcrop at the surface (11). In this region, which we define to be within 70°N to 75°N and 150°W to 170°W, and south of the 300-m isobath (Fig. 2E), water is pumped down from the surface (via the Ekman transport convergence as a result of the prevailing anticyclonic wind stress gradients) and transported laterally by the BG geostrophic flow into the interior gyre (9, 11). Observations suggest that the NCS is characterized by the strongest time-mean Ekman downwelling in the entire Canada Basin, with downwelling rates averaging around 20 m year−1, which corresponds to a vertical Ekman flux of around 0.05 Sv (1 Sv = 106 m3 s−1) for the region (12). This strong downwelling, associated with the region of maximum strength of the prevailing easterlies, takes place year-round with some interannual variability, but no significant trend over 2003–2014 [see Figs. 4 to 6 in (12)].

A major oceanographic feature of relevance in the NCS is a surface front in the vicinity of the Chukchi slope. The front marks the lateral transition between relatively warm (in summer/fall) and salty surface waters (and a deeper mixed layer) to the south, and cool and fresh surface waters (and a shallower mixed layer) to the north, toward the interior of the BG freshwater center. Water at the surface on the south side of the front is transferred below the mixed layer and into the interior halocline by subduction: vertical Ekman pumping plus lateral induction. It should be noted that there are likely other physical mechanisms at play in this important region that depend on the details of surface buoyancy forcing and sea ice state [for example, (13, 14)], local winds, and properties, dynamics, and stability of regional boundary currents [for example, (8, 15–17)]. The ventilation rate from this region (combination of Ekman downwelling and lateral induction) is estimated to be around 0.2 Sv (11). The cause of the warming halocline can be discerned by examining surface ocean temperatures over this region of maximum subduction, the portal for halocline ventilation.

23
Arctic sea ice / Re: The 2020/2021 freezing season
« on: January 03, 2021, 06:16:41 PM »
A possible candidate is upwelling.
http://oceanmotion.org/html/background/upwelling-and-downwelling.htm

Meanwhile in the Beaufort the warm layer is even thicker below whoi itp120

24
Arctic sea ice / Re: What the Buoys are telling
« on: January 03, 2021, 12:07:44 PM »
Ingenious method.

Finishing off the 3hour data with 2015 and 2016.
These animations should be seen as a very rough guide from raw data. In many years the buoys don't appear to continue their paths through december to the following january so this method may be losing some data. Will take a look at the full data directories from 2011-2019 before doing any quality control. If anyone else feels like checking some individual buoy start and end dates, please don't hesitate. https://iabp.apl.uw.edu/Data_Products/BUOY_DATA/

well here is a closer look at IABP1920 from 1979.  Quite a bit slower than mosaic.

25
Arctic sea ice / Re: What the Buoys are telling
« on: January 02, 2021, 08:52:38 PM »
IABP buoys 2012-2014.

26
Arctic sea ice / Re: What the Buoys are telling
« on: January 02, 2021, 08:42:23 PM »
That's good. Arguably colours work better than arrow length with a moving image, particularly when the arrows overlap. Colours on their own are tricky to interpret though without a direction indicator. The two combined are best.

A quick look at whoi itp121. Here comparing temperature and density profiles from 7m-250m. In particular looking to see if there was a density layer at around 200m that matched temperature. It seems not. Wondering if there was detectable wave motion in the pacific layer.

27
Arctic sea ice / Re: The 2020/2021 freezing season
« on: January 02, 2021, 12:10:16 PM »
A comparison of 2017, 2018 and 2020 freezing seasons using amsr2-uhh

28
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: December 31, 2020, 05:50:07 PM »
Split in the Fram funnel or trick of the light?

29
Arctic sea ice / Re: The 2020/2021 freezing season
« on: December 31, 2020, 03:31:54 PM »
Here using the interferometry method to identify areas with more movement. Grey areas are relatively stationary with brighter and darker areas tending to move more. That FYI/SYI edge may always be under more stress than other areas. Continuous ridging?
Ascat day301-362 RGB composite from 1,2 and 3 day difference (grain extract in GIMP)
forgot this: <add 128 neutral gray to avoid negative color numbers> hence the very dark colours

30
Arctic sea ice / Re: What the Buoys are telling
« on: December 31, 2020, 01:43:29 PM »
The first thing I tried was loading all the data at once expecting a nice progressive pattern of buoy paths. What I got was a mess of lines. Separation by colouring years differently helped a little but the data needs careful attention. Examining the directories one at a time is relatively clean and reasonably quick. After all, there are only a few people interested enough to watch the animations.
Eventually I will try to put them all together if it looks like it would tell us anything. My interest is more in the detailed movements, inertial oscillations, tides. Osi-saf already does tracking, though not back to 1979.

@SimonF92, conversion to utm.lat/lon might help your centroid problem

31
Arctic sea ice / Re: The 2020/2021 freezing season
« on: December 30, 2020, 11:11:02 PM »
awi amsr2 dec29-30

A very close look at the 3 wave layers in the white band (10MB for full res) dec30
16bit gimp to png
https://earth.esa.int/web/guest/missions/esa-operational-eo-missions/ers/instruments/sar/applications/radar-courses/content-2
Quote
Different surface features exhibit different scattering characteristics:
urban areas: very strong backscatter
forest: intermediate backscatter
calm water: smooth surface, low backscatter
rough sea: increased backscatter due to wind and current effects


The radar backscattering coefficient σ 0 provides information about the imaged surface. It is a function of:
- radar observation parameters:
(frequency f, polarisation p and incidence angle of the electromagnetic waves emitted);
-surface parameters:
(roughness, geometric shape and dielectric properties of the target).

Influence of frequency

The frequency of the incident radiation determines:
- the penetrationdepth of the waves for the target imaged;
- the relative roughness of the surface considered.

Penetration depth tends to be longer with longer wavelengths. If we consider the example of a forest, the radiation will only penetrate the first leaves on top of the trees if using the X-band (λ = 3 cm). The information content of the image is related to the top layer and the crown of the trees. On the other hand, in the case of L-band (λ = 23 cm), the radiation penetrates leaves and small branches; the information content of the image is then related to branches and eventually tree trunks.

The same phenomenon applies to various types of surfaces or targets (see the figure).

But it should be noted that:
- penetration depth is also related to the moisture of the target;
- microwaves do not penetrate water more than a few millimeters.

Influence of polarization
Polarization describes the orientation of the electric field component of an electromagnetic wave. Imaging radars can have different polarization configurations.

However, linear polarization configurations HH, VV, HV, VH are more commonly used. The first term corresponds to the polarization of the emitted radiation, the second term to the received radiation, so that XHV refers to X band, H transmit, and V receive for example.

In certain specific cases, polarization can provide information on different layers of the target, for example flooded vegetation. The penetration depth of the radar wave varies with the polarization chosen.

Polarization may provide information on the form and the orientation of small scattering elements that compose the surface or target.

More than one bounce of backscattering tends to depolarize the pulse, so that the cross polarized return in this case would be larger than with single bounce reflection.

Influence of roughness
Roughness is a relative concept depending upon wavelength and incidence angle.
A surface is considered "rough" if its surface structure has dimensions that are comparable to the incident wavelength.

32
Arctic sea ice / Re: What the Buoys are telling
« on: December 30, 2020, 09:57:23 PM »
yes.
2008-2010. TPD struggling for a while in 2010.
Took the labels out and started limiting dates to 01/01 to 01/01.

33
Arctic sea ice / Re: What the Buoys are telling
« on: December 30, 2020, 06:28:29 PM »
2005-2007. 2007 gets a special mention for appearing to almost complete a small gyre in one year.
2006 2415, 9115, 11247,
2007 6620

34
Arctic sea ice / Re: What the Buoys are telling
« on: December 30, 2020, 04:48:56 PM »
Excellent. All it needs is the arrows ;) That looks a bit like the mosaic trip in yellow

Here are 2001-2004
2001 22206, 19579
2002 5315, 8063

35
Arctic sea ice / Re: The 2020/2021 freezing season
« on: December 30, 2020, 01:17:46 PM »
-- Was this ice retreat wind-driven?  If so, then it indicates to me the ice front in that area was really fragmentary and weak in its nature in mid December. <>
Yes. There are similarities with 2016. Note the refreeze south of the wind driven ice front (see #953 above)
Is it melting? In my view ice is always melting along much of the West Spitzbergen current. During most winters drift speed and thickness is enough that it is not visible from above except (imo) occasionally along the shelf break north of FJL.

amsr2-uhh comparison of 2020 and 2016, dec20-29

36
Arctic sea ice / Re: What the Buoys are telling
« on: December 29, 2020, 08:59:12 PM »
For cases where the data results in interpolations and big jumps, perhaps a good solution would be to clean the data by changing the buoy number for each consecutive section.

For example
11252   93   12   155.5   72.291   -148.553
11252   93   15   155.625   72.286   -148.552
11252   93   18   155.75   72.285   -148.558
112520   94   15   299.625   74.243   -84.608
112520  94   18   299.75   74.243   -84.605

This would need to be done manually, but just once, and then the data files can be shared in one repository (or attached to a forum post). Renumbering can be triggered by big jumps in time as well as big jumps in space.
If you (uniq or Simon) upload a sample file or a link to one I can try to assess how work-intensive this process would be and if it can be partly automated.
3hourly data is about 330MB uncompressed. I suppose this online show and tell is one way of compiling a list of bad buoys.

@SimonF92. Had a quick look at the dataset creation code but checking it would be a bit of a diversion from the ani project + my py isn't up to it.

Here is the 1998 directory. Laptev cluster almost makes it to the fram, the beaufort cluster started further east in oct1997 and did a further 180° before heading north.

1999 directory
check for 2003 data

2000 dir
1301 takes the Nares strait.

37
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: December 29, 2020, 03:14:16 PM »
Regarding said "big block", now that the wind is blowing up the strait I noticed it is not behaving like its neighbors. It has the tendency to move away from the funnel more easily - could it be that its surface has some tall features that catch the wind in force?
Followed that MYI with the red dot over the last few months. In some ways the ice is its own worst enemy. The animation is best viewed at half speed.
Yesterday's polarview S1B

38
Arctic sea ice / Re: What the Buoys are telling
« on: December 29, 2020, 03:01:52 PM »
A great contribution :)
Central Arctic is the big one for me and daily will do fine for now. I'll check the older animations close up before attempting to look at 3hr velocity. Inertial oscillations may always have been present at a similar magnitude.

1997 directory
The Laptev cluster making its way to the Fram
26695 and 17987 problematic

39
Arctic sea ice / Re: What the Buoys are telling
« on: December 29, 2020, 02:12:50 PM »
Curious about high drift in 2011 so jumped forward to take a look. That directory may need some quality control.
Slow animation to help identify bad buoys.
A quick, but possibly bad, way to deal with it might be to remove any buoys with drift above, say, 5km/h. iirc 3.7km/h was the max drift before reaching the Fram. There is also the issue of buoys in open water to consider.

40
Arctic sea ice / Re: What the Buoys are telling
« on: December 29, 2020, 12:55:43 PM »
1996 directory
A nice cluster in northern Laptev. Might compare well with mosaic.

41
Arctic sea ice / Re: What the Buoys are telling
« on: December 29, 2020, 12:04:39 PM »
11252 data jumps from yr93day155 to yr94day299.  gganimate interpolates with a straight line
Quote
BuoyID Year Hour   DOY      Lat          Lon
11252   93   12   155.5   72.291   -148.553
11252   93   15   155.625   72.286   -148.552
11252   93   18   155.75   72.285   -148.558
11252   94   15   299.625   74.243   -84.608
11252   94   18   299.75   74.243   -84.605
.

dir1995 It seems there is not so much movement but the data only runs from jan-july. The ani has the same number of frames so probably drift looks slower.

42
Arctic sea ice / Re: What the Buoys are telling
« on: December 28, 2020, 09:29:11 PM »
1994 dir. Contains 92-95
check 11252

43
Arctic sea ice / Re: What the Buoys are telling
« on: December 28, 2020, 09:04:04 PM »
1993 directory contains a lot of 1994
possibly due to 5318

44
Arctic sea ice / Re: What the Buoys are telling
« on: December 28, 2020, 08:29:59 PM »
1992 directory. The fjl cluster pops up in jan, data appears to end on day213.
possible that duplicated december data is causing the problems?

45
Arctic sea ice / Re: What the Buoys are telling
« on: December 28, 2020, 08:18:42 PM »
With 1990's data I get less animation problems when presenting buoys from one directory at a time.
Here is the 1991 directory. A great cluster north of FJL

46
Arctic sea ice / Re: What the Buoys are telling
« on: December 28, 2020, 03:42:17 PM »
Tbuoy temperature profiles, dec1-28. Not too cold for a couple of days over the festive season at ~87N, peaking at around -1.3C on dec24, up from -36C on dec20.
edited gif to 504px

47
Arctic sea ice / Re: The 2020/2021 freezing season
« on: December 28, 2020, 11:02:28 AM »
Thanks for the animation Aluminium.
Interesting that the Barents looks like it is freezing despite the southerly winds. Checking on nullschool, those surface winds leave the coast at -17C, rising to -5C as they cross mostly open water.
Sentinel S1B view of that area from polarview The wind driven ice edge is darker to the left, open water is bright to the far right. click for full res.

48
Arctic sea ice / Re: What the Buoys are telling
« on: December 27, 2020, 10:19:50 PM »
In 1990 iabp7049 went down the Nares strait.
12780 has a gap in the data.

49
Arctic sea ice / Re: What the Buoys are telling
« on: December 26, 2020, 10:50:53 PM »
A possible increase in drift speed after 2012. Thinking about the sampling rate, a daily sample will miss any inertial oscillations and/or tidal movement. One way to avoid that would be to run a program to add 3hr drift and/or velocity to all file rows before calculating the averages. Will certainly give your computer a good work out but you'd only have to do it once.

Here looking at whoi itp113 hoping it doesn't trash its profiler on the shallower Northwind Ridge/Chukchi Plateau

edit: profiler battery looking low.

50
Arctic sea ice / Re: The 2020/2021 freezing season
« on: December 26, 2020, 08:19:10 PM »
An attempt to identify the white band in worldview by overlaying S1B onto a very enlarged ascat and suomi npp viirs brightness temperature band15 night. All from dec14, the nearest clear(ish) day.

Also an overlay of dec26 S1B onto dec14 at 50% transparent.

On a different note, the Atlantic front is still very sensitive to wind direction.
amsr2 awi v103 dec18-26(early)

Mosaic floe2 at ~87N also reacting to yesterday's 50km/h southerlies.

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