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A-Team

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Re: The 2018 melting season
« Reply #750 on: May 20, 2018, 11:13:48 PM »
UB SMOS consistently indicates thin ice (≤0.5m) only in the northwest corner of Hudson Bay for the last three months. UH SMOS seems to have knocked off for the year on April 15th.

The slideshow compares (1) the overall locations of NH thin ice on 19 May 2018 with the (2) locations given by averaging SMOS colors over the last 80 days (which goes off-key because of faulty UB palette construction) and (3) locations of thin ice colored by their most recent status.

Technical note: the last slide is made by deleting ice >0.5m thick to transparency, then stacking with most recent date on top, then capturing the colors that show through.


The three approaches converge on the usual suspect expected areas of early Arctic Ocean melt, SW Beaufort, SE Chukchi, Laptev periphery, Kara and Svalbard-FJL-N Barents.

Jaxa 36V,36H,18V provides a more nuanced view of Hudson Bay, starting to capture ice of a different (dodgier) status in the southwest and south over the last couple of weeks.

UH AMSR2 confirms this at 3.125 km resolution after discounting non-persistent effects of passing weather.
« Last Edit: May 21, 2018, 03:59:23 PM by A-Team »

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Re: The 2018 melting season
« Reply #751 on: May 21, 2018, 10:18:19 AM »
Someone already mentioned the Hot Blob developing in the North Atlantic. Although the Cold Areas have also expanded quite a bit (mind You these are just Sea Surface Temp Anomalies- up to 2 m Depth, if I'm correct).
This will certainly churn out some Storms heading into the Arctic, the Question is 1) how and 2) when will it affect direct Heat Transport through the Gulf up to Svalbard & Arctic.

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Re: The 2018 melting season
« Reply #752 on: May 21, 2018, 11:33:30 AM »
Just the lack of sunshine on the waters below (for the areas under constant low pressure formation) will keep the sst's suppressed. It might look dramatic ,esp. hard up against positive anoms, but it would disappear very quickly once 'normal services' are resumed.

The growth of the positive anoms are different as we know hurricanes feed of the ocean below so any little help in their formation will lead them to bomb into big storms. The storms will trawl up waters from deeper down but we appear to have built quite a reserve of warmth in the tropical Atlantic?

Why is this important? Well we all know where the storms end up! Be it Baffin or Fram we could see plenty of energy headed north in late Aug/early Sept.

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Re: The 2018 melting season
« Reply #753 on: May 21, 2018, 12:03:52 PM »
Pacific side, 105 hours, May 16-20.  I went with an mp4 to preserve detail.  Low clouds are clearing out as a "cleaner" high pressure appears to be taking over.  If the ECMWF is to be believed, it will have some staying power.

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Re: The 2018 melting season
« Reply #754 on: May 21, 2018, 04:38:15 PM »
It seems like the lack of Greenland Sea ice this year coupled with the warmth in the very far NATL has sufficed to produce a ridiculous vortex. Record-setting?

Wonder how long it persists into the season / maybe it is a "new thing" of the ridiculous SST / snowfall distribution across the ATL and its peripheral continents?

In any case, I would suggest that the presence of ^ indicates that the high Arctic is going to lose its "guts" of the cryosphere increasingly often this summer as the main cold pole co-locates to the periphery of wherever ^ vortex resides.

It should also be noted that models are setting up an absolute torch over far northern Europe / Scandinavia in the extended...

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Re: The 2018 melting season
« Reply #755 on: May 21, 2018, 06:12:43 PM »
Below is a cloud-free Modis mosaic of the Arctic from May 6-14 images put together by the Canadian Ice Service. It extends down to approximately 55ºN and so picks up most of the remaining NH high albedo snow and ice of the planet's declining refrigerator.

https://pbs.twimg.com/media/DdX63EsVQAEBdtZ.jpg:large (needs 60º cw rotation)

It's shown slightly cropped with contrast adjustments below, along with the same view from Ascat and Jaxa, both from May 20th.

bbr2314

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Re: The 2018 melting season
« Reply #756 on: May 21, 2018, 06:23:59 PM »
I think the ^ images show something interesting / possibly confirm a differential in 2018 vs. the major melts of yesteryear like 2012.

2011 and especially 2012 were driven by early melt-outs of continental snowpack in conjunction with some oceanic warming. But the early melt of continental snowpack was critical, especially across North America in 2012, in allowing airmass-driven melting to begin across the Arctic far earlier than normal.

2018 is very different from these years. Our numbers are lower, but the continental situation this spring has been a literal climate away from 2011 / 2012. Forgetting comparisons versus "normal", volume of SWE and snow extent were both *massively* above 2011 and 2012. But Arctic sea ice was even lower than both of those years!

I think this has important implications as we head deeper into the melt season because the way melt is now progressing is changing. We are now seeing some muting of airmass-driven melt (at least prior to solstice, this is likely to change as continental snows melt out by July). But melt driven by increasing oceanic heat has MORE than made up for this deficit. And, surprisingly to some, this has been most apparent in areas of the pack that are very close to 90N -- namely, both the Bering, and the high ATL seas (Barents/Greenland).

The GFS et al have been far too aggressive in their depicted warmings over the Arctic in recent weeks and I think this is because snowpack has been surprisingly resistant to melt (again, this will change). But perhaps the trend so far this spring and the comparison / contrast vs. 2011 / 2012 indicate that we are likely to see much more cyclonic activity this fall, in keeping with the ever-increasing oceanic heat content? The contrast with relatively cooler continental airmasses vs the other years could mean that the gradient is even worse in 2018 / cyclones are stronger.

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Re: The 2018 melting season
« Reply #757 on: May 21, 2018, 06:24:04 PM »
What online archive should we use this spring for near-real time melt ponds? So many papers but no daily archive? Looking in the rear view mirror provides little of value during times of rapid change:

Revisiting the potential of melt pond fraction as predictor for seasonal Arctic sea ice extent minimum
Jiping Liu et al 19 May 2015
http://iopscience.iop.org/article/10.1088/1748-9326/10/5/054017/meta

A recent modeling study [Schroder 2014] that employed a prognostic melt pond model in a stand-alone sea ice model found that September Arctic sea ice extent can be accurately predicted from the melt pond fraction in May. Here we show that satellite observations show no evidence of predictive skill in May. However, we find that a significantly strong relationship (high predictability) first emerges as the melt pond fraction is integrated from early May to late June, with a persistent strong relationship only occurring after late July.

Melt pond fraction is derived from MODIS surface reflectance as processed by a neural network using spectral characteristics of melt ponds relative to open water, snow and ice. The melt pond fraction is available at 8 day interval from 9 May to 6 September with a spatial resolution of 12.5 km from 2000 to 2011 [Rösel et al 2012].

The observed climatological melt pond fraction is ~11% in early May and increases rapidly in late May and June (~23% in late June and reaching a peak ~25% in early July), followed by a gradual decrease (still retaining ~20% in late August and early September) as shown in Fig1a.

This archive is based on Modis but has no data beyond Sept 2011:
  https://icdc.cen.uni-hamburg.de/1/daten/cryosphere/arctic-meltponds.html
  ftp://ftp-icdc.cen.uni-hamburg.de/arctic_meltponds/

The impact of melt ponds on microwave brightness temperatures and sea-ice concentrations
S Kern et al Sept 2016
https://www.the-cryosphere.net/10/2217/2016/tc-10-2217-2016.pdf

Sea-ice concentrations derived from satellite microwave brightness temperatures are less accurate during summer. In the Arctic Ocean the lack of accuracy is primarily caused by melt ponds, but also by changes in the properties of snow and the sea-ice surface itself. We investigate the sensitivity of eight sea-ice concentration retrieval algorithms to melt ponds by comparing sea-ice concentration with the melt-pond fraction.

One potential reason for the reduced accuracy is the change in microphysical properties inside the sea ice, for instance, the desalination of the sea ice during the melt process or the flushing of air voids in multiyear ice with meltwater and other melt processes (Scharien 2010).

The three key surface features of summer melt on Arctic sea ice are a metamorphou wet snow cover, a porous, wet sea-ice surface, and melt ponds. During summer, the snow cover on sea ice is usually wet or even saturated with meltwater. Its density is usually considerably larger during summer than during winter.

Diurnal melt–refreeze cycles,  episodes of intermittent melting and refreezing of the snow, which is a common phenomenon during late spring, result in an increase in the snow grain size. Wet snow is an efficient absorber of microwave radiation and has a microwave emissivity close to 1. It can effectively block microwave emission from underneath.

Satellite microwave sensors which have been used for sea-ice concentration retrieval allow for footprint sizes between 5 and 70 km. Melt ponds, cracks, and leads are therefore sub-footprint size surface features, and cannot be resolved individually. A satellite brightness temperature measurement of a mixed scene is therefore composed of contributions from the open water, i.e., cracks, leads, melt ponds, and from the (snow covered) sea ice.

This has two main consequences for a sea-ice concentration product computed from such coarse-resolution satellite measurements. The sea-ice concentration in the presence of melt ponds is likely to be underestimated   because melt ponds are seen as open water. Whether the footprint contains, for example, (case A) 100 % sea ice with 40 % melt ponds or (case B) 60% sea ice with 40 % open water from leads and openings, is ambiguous. In both cases, satellite microwave radiometry retrieves 60 % sea-ice concentration because the net sea-ice surface fraction of sea ice in the grid cells is 60 %   

Melt pond fraction and spectral sea ice albedo retrieval from MERIS data
L Istomina et al
The Cryosphere, 9, 1551–1566, doi:10.5194/tc-9-1551-2015, 2015a.
The Cryosphere, 9, 1567– 1578, doi:10.5194/tc-9-1567-2015, 2015b.

The data used for the present study are the pond fraction and broadband sea ice albedo swath data products retrieved from MERIS (Medium Resolution Imaging Spectrometer) swath Level 1b data over the ice-covered Arctic Ocean using the MPD retrieval. The present chapter presents a short summary of the MPD retrieval. T

The full description of the algorithm can be found in EP Zege et al
https://epic.awi.de/38709/1/1-s20-S003442571500108X-main.pdf

"The input to the current version of the MPD algorithm is the MERIS Level 1B data, including the radiance coefficients at ten wavelengths and the solar and observation angles (zenith and azimuth). Also, specific parameters describing surface and atmospheric state can be set in a configuration input file. The software output is the map of the melt ponds area fraction and the spectral albedo of sea-ice in HDF5 format. Currently, the MPD code is arranged as a Linux console application and works in the MERIS processing chain in theUniversity of Bremen, providing a comprehensive melt pond data product based on the complete MERIS data set 2002–2012

Signature of Arctic first-year ice melt pond fraction in X-band SAR imagery
AF Fors et al March 2017
The Cryosphere 11(2) DOI 10.5194/tc-11-755-2017
 
Melt pond fractions retrieved from a helicopter-borne camera system were compared to polarimetric features extracted from four dual-polarimetric X-band SAR scenes, revealing significant relationships. The correlations were strongly dependent on wind speed and SAR incidence angle. Co-polarization ratio was found to be the most promising SAR feature for melt pond fraction estimation at intermediate wind speeds.

A spectral mixture analysis approach to quantify Arctic first-year sea ice melt pond fraction using QuickBird and MODIS reflectance data
JJ Yackel et al Sept 2017 DOI10.1016/j.rse.2017.09.030

Despite its requirement for thermodynamic sea ice modeling,measurement of melt pond areal coverage using satellite remote sensing has proven difficult due to significantspatiotemporal variability in the timing and evolution of melt ponds. Less than optimal results from prior studiesemploying a spectral mixture analysis (SMA) towards the determination of melt pond areal coverage from sa-tellite remote sensing data provided the incentive for a multiple endmember spectral mixture analysis (MESMA)approach. The MESMA was performed on Moderate Resolution Imaging Spectroradiometer (MODIS) imageryusing endmember spectra obtained from atmospherically corrected coincident high resolution imagery, surfaceobservations and modeling. Results were validated against a high resolution Quickbird image acquired coin-cident to the MODIS image.

Melt ponds over Arctic sea ice
D Flocco March 2017
http://blogs.reading.ac.uk/weather-and-climate-at-reading/2017/melt-ponds-over-arctic-sea-ice/

Where ponds form, the ice beneath becomes thinner due to increased melting. Towards the end of the summer, the air temperature drops and a thin layer of ice forms over melt ponds. The ponds’ melt water trapped in the ice acts as a heat store and does not allow the underlying ice to start thickening until all the pond’s water is frozen. Ponds are up to 1.5 m deep and it can take over two months to freeze their volume of water.
« Last Edit: May 21, 2018, 06:31:15 PM by A-Team »

Neven

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Re: The 2018 melting season
« Reply #758 on: May 22, 2018, 12:26:34 AM »
High pressure has been reduced, but refuses to leave the CAB/Beaufort. With a low pressure over the Laptev, a small dipole is setting up with isobars pointing to winds blowing the ice away from the Siberian coast (but towards the CAA). Here's the ECMWF forecast for the coming six days, I've added a couple of white arrows to show how the winds will blow.

Let's see how much movement there is. I had expected more open water in the Beaufort Sea by now, but maybe the winds have been blowing too laterally to the coast.
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Re: The 2018 melting season
« Reply #759 on: May 22, 2018, 01:08:06 AM »
since we don't have so many cameras showing good images of the ice surfaces i thought to post this one in barrows that IMO shows melt-ponding at a temperature of -3C.

somehow it can be assumed that would look similar in other places and especially where temps are at or slightly above freezing point.

since i'm not an ice-man this assumption could be an error, gladly learning if so, just share your take on the subject ;)

uniquorn

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Re: The 2018 melting season
« Reply #760 on: May 22, 2018, 01:13:09 AM »
A comparison of may2017 to may2018 using ascat. There are many similarities in the ice movement so far.
2017(left) shows the lift off of MYI from the CAA ready to start it's way around the coast of the Beaufort Sea. It looks like the same movement will continue this year and that string of MYI is already exposed to open water in the Chukchi.

On the Atlantic side the area north of Svalbard has opened up significantly during May this year, the younger (darker) ice of the 'Kara tongue' perhaps struggling against southerly winds and warmer water. It will be interesting to see what happens if it meets the area north of Greenland where the weaker ice from the February storm still shows. Overall there is now less extent in the Barents than last year.
Nares strait was already open for export in 2017 and it didn't close until March 2018 (I think). That long year of MYI export leaving thinner ice still visible in the Lincoln sea.

tech notes
imagej: brightness/contrast 41,255 clahe 63,256,2.2

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Re: The 2018 melting season
« Reply #761 on: May 22, 2018, 02:28:30 AM »
since we don't have so many cameras showing good images of the ice surfaces i thought to post this one in barrows that IMO shows melt-ponding at a temperature of -3C.

somehow it can be assumed that would look similar in other places and especially where temps are at or slightly above freezing point.

since i'm not an ice-man this assumption could be an error, gladly learning if so, just share your take on the subject ;)

Looks to me like the melt ponds are close to the coast - perhaps the impact of nearby landmass absorbing a lot more solar heat.  The horizon looks much brighter and whiter.
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Re: The 2018 melting season
« Reply #762 on: May 22, 2018, 02:36:35 AM »
High pressure has been reduced, but refuses to leave the CAB/Beaufort. With a low pressure over the Laptev, a small dipole is setting up with isobars pointing to winds blowing the ice away from the Siberian coast (but towards the CAA). Here's the ECMWF forecast for the coming six days, I've added a couple of white arrows to show how the winds will blow.

Let's see how much movement there is. I had expected more open water in the Beaufort Sea by now, but maybe the winds have been blowing too laterally to the coast.

And enough heat for some substantial surface melting in Siberian and Laptev regions. 
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Re: The 2018 melting season
« Reply #763 on: May 22, 2018, 02:38:46 AM »
since we don't have so many cameras showing good images of the ice surfaces i thought to post this one in barrows that IMO shows melt-ponding at a temperature of -3C.

somehow it can be assumed that would look similar in other places and especially where temps are at or slightly above freezing point.

since i'm not an ice-man this assumption could be an error, gladly learning if so, just share your take on the subject ;)

Looks to me like the melt ponds are close to the coast - perhaps the impact of nearby landmass absorbing a lot more solar heat.  The horizon looks much brighter and whiter.
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Re: The 2018 melting season
« Reply #764 on: May 22, 2018, 02:42:03 AM »
High pressure has been reduced, but refuses to leave the CAB/Beaufort. With a low pressure over the Laptev, a small dipole is setting up with isobars pointing to winds blowing the ice away from the Siberian coast (but towards the CAA). Here's the ECMWF forecast for the coming six days, I've added a couple of white arrows to show how the winds will blow.

Let's see how much movement there is. I had expected more open water in the Beaufort Sea by now, but maybe the winds have been blowing too laterally to the coast.
I'd say we watch the Barentz closely as well.  Wind and wave action from those two lows may have a pronounced affect the already weak ice between FJL and Nova Zemlya.
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Re: The 2018 melting season
« Reply #765 on: May 22, 2018, 10:18:42 AM »
Whoa!

Has GFS "thrown a rod"?

On May 30th, it is indicating the west shore of Hudson Bay will approach 100 degrees and I'm talking DegF, not DegK :)

If the prediction turns out to be accurate, the white bears need to find another source of subsistence for sure.

How many 100 degree days will it take to melt the SI in the Bay?

P.S. I'm thinking about buying some land on Baffin Island and start growing potatoes.


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Re: The 2018 melting season
« Reply #766 on: May 22, 2018, 02:53:40 PM »
since we don't have so many cameras showing good images of the ice surfaces i thought to post this one in barrows that IMO shows melt-ponding at a temperature of -3C.

somehow it can be assumed that would look similar in other places and especially where temps are at or slightly above freezing point.

since i'm not an ice-man this assumption could be an error, gladly learning if so, just share your take on the subject ;)

 The ice along pretty much the entire north coast of Alaska looks suspiciously blue on Worldview today.
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Re: The 2018 melting season
« Reply #767 on: May 22, 2018, 03:21:04 PM »
uniquorn....

The Atlantic side of the Arctic looks particularly vulnerable when compared to last year. A lot of thin FYI. My guess is we will end up with more open water on this side of the CAB than ever before. Normally, we would expect ice moving towards the Fram to replenish this area but SST are extraordinarily high with open water north of Svalbard throughout the winter.

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Re: The 2018 melting season
« Reply #768 on: May 22, 2018, 04:14:11 PM »
If the Atlantic front retreated sufficiently during the course of summer, there is a possibility that the remainder of ice would be out of reach of the transpolar drift. It could even happen that CAB ice gets pushed into the Beaufort Gyre, either way, ice gets more in contact with sun. That is, of course, an outlier possibility but the situation has also changed dramatically from the past.

uniquorn....

The Atlantic side of the Arctic looks particularly vulnerable when compared to last year. A lot of thin FYI. My guess is we will end up with more open water on this side of the CAB than ever before. Normally, we would expect ice moving towards the Fram to replenish this area but SST are extraordinarily high with open water north of Svalbard throughout the winter.

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Re: The 2018 melting season
« Reply #769 on: May 22, 2018, 04:21:34 PM »
Thursday's ecmwf wam(wave) forecast from windy certainly won't help.
edit: Looks pretty rough near the Kane Basin arch too

Quite a few red areas on the pacific side using Worldview terra/modis bands 3,6,7. I'm no expert at spotting melt ponds though.
« Last Edit: May 22, 2018, 07:57:23 PM by uniquorn »

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Re: The 2018 melting season
« Reply #770 on: May 22, 2018, 10:20:32 PM »
>out of reach of transpolar drift

There has been no transpolar drift whatsoever in 2017-18 and none is in the works.

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Re: The 2018 melting season
« Reply #771 on: May 23, 2018, 02:25:21 AM »
Thanks A-team!

Your .mp4 "233 days of anti-transpolar drift 2017-2018" is probably going to become my go-to reference for where last year's remaining ice has drifted since.

I downloaded the movie and by dragging the cursor backwards & forwards through the time sequence can easily track features visually to see how the different parts of the ice pack have moved. Much appreciated!  :)

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Re: The 2018 melting season
« Reply #772 on: May 23, 2018, 03:07:25 AM »
For the multi-year ice I tend to conceptualize the drift pattern - both this past year & previous several years - slightly differently from the canonical description of a Beaufort gyre +trans-polar drift (agree, the latter not much seen if at all these years).

Instead, I see it as a prevalent drift from the (central) Russian side to the (central) Canadian side that compresses the ice against the Canadian Arctic coastline but also with faster drifts on both the Atlantic & Alaskan sides - the former in a similar direction but the latter bringing the ice back in the opposite direction, towards Russia.

The fast Atlantic side drift sweeps that ice through the Fram Strait, unless it melts out first. This is in pretty much in the same direction as the prevalent central drift only faster because the ice isn't blocked.

The drift on the Alaskan side sweeps the ice fast in the opposite direction to the central & Atlantic-side drifts, in a direction parallel to the Alaskan Arctic coastline & in the direction of Russia.

The sum of the central+Alaskan-side drifts is re-describing the Beaufort gyre, obviously, but acknowledges that the drift back towards Russia is seen to be much faster because it isn't blocked by land, namely the Canadian Arctic coastline. (There is a small leak through the Nares Strait though.)


Is this a useful way now to broadly conceptualize the Arctic sea ice movement given that there is no longer significant a) trans-polar drift, or b) sea ice that survives multi-year cycles around the Beaufort gyre?
« Last Edit: May 23, 2018, 03:19:07 AM by slow wing »

uniquorn

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Re: The 2018 melting season
« Reply #773 on: May 23, 2018, 11:47:03 AM »
I would add another arrow from the Kara Sea into the CAB. The volume depends on how quickly Kara melts out.

With a week of warmer winds forecast for the Laptev Sea, here is Worldview terra/modis may15-23. The next few days should give more indication of any anomalously thicker areas.

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Re: The 2018 melting season
« Reply #774 on: May 23, 2018, 02:20:15 PM »
Unless I don't understand how to interpret this Arctic ice image, it seems the Laptev Sea has a lot of vulnerable 1st year ice that extends well into the CAB along Severnaya Zemlya.

Something to watch?

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Re: The 2018 melting season
« Reply #775 on: May 23, 2018, 04:03:34 PM »
NACK: the GFS forecast shows pretty similar temperatures near the sea as ECMWF; the difference is about 100 km inland in Ontario and Manitoba.

I have a potato plant growing on Baffin Island right now. It could be a bit happier -- it hasn't been very sunny this month. I expect my May heating bill to be on par with April's despite the rather warmer temperatures.

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Re: The 2018 melting season
« Reply #776 on: May 23, 2018, 04:49:52 PM »
Right, ice motion is highly non-uniform and difficult even to describe because of feature distortion over time, with overall mobility hard to compare year on year. ECMWF --> MSLP --> wind --| ice motion because form drag is highly variable and largely unknown.

It is a very poor idea to use averaged gridded ice velocity vectors because of uncorrelated commutativity cancellation issues discussed at length up-forum yet you will see this all over, for example on the WHOI buoy home page.

The six years available for Ascat on May 22nd are shown below. This year, on this date, looks most like 2016. We have not seen the sharp elbow before in the Chukchi of the Beaufort stringer of CAA thick coastal ice. This resulted from strong persistent westward zonal (latitudinal) winds along the Alaskan coast, combined with southeast Chukchi lift-off and surge from the Bering Sea.

Quote
Laptev ice along SZ is FYI, to melt out
Right. Basically all the darker ice on Ascat is FYI which will melt out by September, including the non-peripheral components. Add to this the brighter ice that has been transported to warmer seas and you have a rough prediction for the fall. The 'union jack' coloration of Ascat portrays that fairly well.
« Last Edit: May 23, 2018, 05:03:18 PM by A-Team »

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Re: The 2018 melting season
« Reply #777 on: May 23, 2018, 06:36:09 PM »
Here is a first pass at ice classification based on its provenance (origin history) implied by the 233 day time series a couple posts back. Modulo subsequent translocation and plastic deformation, this provides a rough prediction of what ice will remain where in mid-September.

The two Ascat-based posterization slides give a more nuanced version under the assumptions that Ascat roughness ~ ice age ~ ice thickness ~ location coldness ~ susceptibility to melt. That has worked out fairly well for recent years, though the Great Arctic Cyclone of early August 2012 is missing from the Ascat archive available.

Jaxa images come from a very different instrument but its posterization-prediction is not dissimilar from Ascat. It has more potential for melt pond tracking (pinkish regions) but weather artifacts bring in considerable ambiguity.
« Last Edit: May 23, 2018, 06:44:32 PM by A-Team »

Shared Humanity

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Re: The 2018 melting season
« Reply #778 on: May 23, 2018, 09:29:24 PM »
Fantastic images! Thanks.

Lord M Vader

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Re: The 2018 melting season
« Reply #779 on: May 24, 2018, 09:06:04 AM »
Seems like the ESS has started to melt. How unusual is that at this time of year compared to other years?

In the southern part of Chukchi and northern Berings Sea the SSTs are already at a full degree above zero. Imagine how warm those areas might be when refreezing season starts?  :o

subgeometer

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Re: The 2018 melting season
« Reply #780 on: May 24, 2018, 10:12:38 AM »
Wafer Thin refreeze ice north of the Lena delta in the Laptev can't hold out long against current heat influx.. I also made a little gif showing the boundary of the fast ice against a bathymetry map (from the Laptev wiki page) I roughly stretched to match projections

Gary H

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Re: The 2018 melting season
« Reply #781 on: May 24, 2018, 08:41:45 PM »
Will the rather flat trend for the Sept min sea ice extent of the last decade, continue in 2018?

numerobis

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Re: The 2018 melting season
« Reply #782 on: May 24, 2018, 09:24:46 PM »
There's been no statistically significant global warming since last July, so probably.

Stephan

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Re: The 2018 melting season
« Reply #783 on: May 24, 2018, 09:26:36 PM »
As data exist from 1979 on it isn't really wise to use only ten years of ice trends (not for winter maxima or September minima or any other time of the year). As every year is different, and external influence from temperature, waves, cloudiness, water temp. etc. mainly determine the individual year's pattern and melting, a period of only ten years does not give a representative trend line. This short period can only "summarize" the annual variability which maybe leads to a trend line that differs from the long-term climatological trend.
AGW deniers sometimes do "cherry picking" on even a fewer number of years to show the trend they want the public to see.

Greenbelt

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Re: The 2018 melting season
« Reply #784 on: May 24, 2018, 09:40:40 PM »
In fact there's a longer time frame graphic linked on this very site!
https://sites.google.com/site/arcticseaicegraphs/longterm

Gary H

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Re: The 2018 melting season
« Reply #785 on: May 24, 2018, 09:49:28 PM »
Beginning the analysis in 1979 is cherry picking. Why did we stop discussing the decades long increasing trend - leading up to 1979 - in Arctic sea ice extent? Noting that there's been a flat trend here for a decade is simply interesting in the moment. Does it perhaps suggest that we could be ending one cycle and beginning another? Also interesting that the Arctic sea ice volume is rather interesting in the moment.  http://ocean.dmi.dk/arctic/icethickness/thk.uk.php

One can toggle back - I just put May 23, 2008 side by side with yesterday's ice thickness - interesting.

 Graph was in the 1990 IPCC report. 

numerobis

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Re: The 2018 melting season
« Reply #786 on: May 24, 2018, 10:32:27 PM »
Hard to read that photocopy of a 28-year-old document but the scale shows the variability is fully contained in +/- 1 million km^2. So that would put the lowest point on that scale bar (which is below any data point) as being about 5.8 Mkm^2. The minimum was last that high in 2004.

Sorry, did you have a point?

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Re: The 2018 melting season
« Reply #787 on: May 24, 2018, 10:47:48 PM »
Beginning the analysis in 1979 is cherry picking. Why did we stop discussing the decades long increasing trend - leading up to 1979 - in Arctic sea ice extent? Noting that there's been a flat trend here for a decade is simply interesting in the moment. Does it perhaps suggest that we could be ending one cycle and beginning another? Also interesting that the Arctic sea ice volume is rather interesting in the moment.  http://ocean.dmi.dk/arctic/icethickness/thk.uk.php

One can toggle back - I just put May 23, 2008 side by side with yesterday's ice thickness - interesting.

No gary. The flat ten year extent minima curve is the result of an increasingly mobile, fragmented, porous and fragile pack sprawling outwards as it is pummeled by increasingly vigorous weather systems. Composed increasingly of porous spongy ice with layers of frozen surface melt interspersed with snow reducing its density, therefore showing more freeboard to satellite sensors. Also wave slosh and wicking drawing salinity upward into the surface layercake.  These factors are making the modeled thickness and volume figures we are being fed overstate the MASS of frozen H2O in the Arctic ocean, as this process is moving much faster than the science burocracy can move to update the modelling algorithms. Particularly as funding and feasibility of boots on the ice direct measurement to calibrate the models has crashed. In no small part due to big business and political corruption, not to mention it now being near impossible to find floes firm or stable enough to land a plane on or camp on.  ::)
Policy: The diversion of NZ aluminum production to build giant space-mirrors to melt the icecaps and destroy the foolish greed-worshiping cities of man. Thereby returning man to the sea, which he should never have left in the first place.
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Aluminium

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Re: The 2018 melting season
« Reply #788 on: May 24, 2018, 11:22:11 PM »
The flat ten year extent minima curve is the result of an increasingly mobile, fragmented, porous and fragile pack sprawling outwards as it is pummeled by increasingly vigorous weather systems.
The horizontal ten-years trend has no statistically significant difference with the decreasing forty-years trend. Appearance of short horizontal trends can be explained by random fluctuations.

Archimid

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Re: The 2018 melting season
« Reply #789 on: May 24, 2018, 11:31:13 PM »
Gary H. First this discussion is off-topic in the Melting Season thread. I suggest we continue this discussion here:

https://forum.arctic-sea-ice.net/index.php/topic,224.0.html


There we have early satellite images of the period you describe as "decades long increasing trend".

However your true lies on this thread must be refuted, risking the ire of the ASIF gods.

Quote
Beginning the analysis in 1979 is cherry picking.

How is taking the whole sattellite data set cherry picking?

Quote
Why did we stop discussing the decades long increasing trend - leading up to 1979 - in Arctic sea ice extent?

What decades long increasing trend?



Quote
Noting that there's been a flat trend here for a decade is simply interesting in the moment. . Does it perhaps suggest that we could be ending one cycle and beginning another?

Surely there has been a hiatus in extent drop and a shorter hiatus in volume loss. The question is how long it will last and what happens next. Given Arctic temperatures I have no clue why you think the the next step change will be up. The next step will be down and may be the last one.



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Also interesting that the Arctic sea ice volume is rather interesting in the moment.

Interesting? I would call it scary compared to the volume of the 20th century. 

Quote
Graph was in the 1990 IPCC report.

Nice cherry. This cherry is typically associated with climate change deceivers. It seems to me like an averaged annual sea ice extent, for a very narrow set of years. I have to imagine the very slight increase at the beginning is due to larger growth of sea ice in the winter averaged with September losses.
I am an energy reservoir seemingly intent on lowering entropy for self preservation.

Daniel B.

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Re: The 2018 melting season
« Reply #790 on: May 24, 2018, 11:31:40 PM »
The flat ten year extent minima curve is the result of an increasingly mobile, fragmented, porous and fragile pack sprawling outwards as it is pummeled by increasingly vigorous weather systems.
The horizontal ten-years trend has no statistically significant difference with the decreasing forty-years trend. Appearance of short horizontal trends can be explained by random fluctuations.
Neither does the 18-year horizontal trend at the start of the dataset.  The reason there is no statistical difference is due to large inter annual variations.  Almost all the ice loss occurred over a 12-year period from 1996-2007. 

Dharma Rupa

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Re: The 2018 melting season
« Reply #791 on: May 24, 2018, 11:33:11 PM »
Beginning the analysis in 1979 is cherry picking....

What does this have to do with this melting season?

A-Team

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Re: The 2018 melting season
« Reply #792 on: May 24, 2018, 11:37:25 PM »
Back on melt season, a nice contribution from subgeo at #780 in the Laptev region of seasonal landfast ice and its frequent flaw polynyas (which have been studied for decades). The proximal cause is wind-driven shift of the ice pack, with not all of it going along.

The question concerns the relatively consistent position of the break-line -- is it ice thickness, local bathymetry, ice shelf breaks, tidal fluxes, river-lowered salinity, ice reformation-driven haloclines or what.

The first order of business is just pulling together data in terms of time series and overlays. The imagery below supplements Modis ice, land edge and bathymetry that subgeo provided with Jaxa RGB radar, literature review diagrams, Osi-Saf two day wind since March, open water AMSR2 and intermediate ice.

This feature (and a similar one next door on the Kara) are not entirely of academic interest but neither are they pivotal to melt season records and the like.

Technical note: the animation in #780 doesn't play initially because its height of 760 pixels exceeds forum limits. Modis ice images use very little of color space and benefit from contrast tightening.
« Last Edit: May 24, 2018, 11:48:02 PM by A-Team »

Chuck Yokota

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Re: The 2018 melting season
« Reply #793 on: May 24, 2018, 11:45:00 PM »
Beginning the data series in 1979 is in no way cherry picking. It was in fact the first year that satellites made possible the direct observation of the entire Arctic ocean on a daily basis. Prior to that time, data was spotty at best, with vast stretches of the Arctic going unobserved for weeks or months at a time. Prior to 1979, the Arctic sea ice extent numbers were only estimates and extrapolations from sparse observations.

In the decades since 1979, research has endeavored to get a better picture of the Arctic sea ice extent from earlier times. More than a one and a half centuries of whaling ships' logs of the edge of the ice pack, compilation of observations of Arctic expeditions, and proxy information such as examination of sea floor sediments have provided a better picture of the sea ice extent in earlier decades.

They show that the sea ice extent has consistently been larger than the current time, with much more older and thicker sea ice. There is no trace of a 40 year cycle; that is a myth that deniers have invented to cast doubt on the importance of the decline in sea ice during the past 4 decades.

Edit: Sorry for off-topic response.
« Last Edit: May 25, 2018, 12:38:54 AM by Chuck Yokota »

Neven

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Re: The 2018 melting season
« Reply #794 on: May 25, 2018, 12:20:29 AM »
Gary H. First this discussion is off-topic in the Melting Season thread. I suggest we continue this discussion here:

https://forum.arctic-sea-ice.net/index.php/topic,224.0.html

Thanks, Archimid. Let's stay on-topic (2018 melting season, ie now and short term). I would also advise people to not go the Steven Goddard route. I see where it leads to every day before flushing and it ain't pretty.  ;)
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numerobis

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Re: The 2018 melting season
« Reply #795 on: May 25, 2018, 12:26:26 AM »
Back from troll-smashing: man it's been grey and cool (-5C to -10C when the norm is about 0C) in Iqaluit this May -- quite the opposite of April when it was sunny and warm (-5C to -10C when the norm is -10C to -15C).

For about two weeks, Environment Canada has been forecasting temperatures above freezing at the end of 3-5 days. Much like nuclear fusion being just around the corner, temperatures above freezing remain tantalizingly close. The floe edge opened up much closer than usual back in April, but I haven't seen chatter of any unusual melting -- quite the opposite.

Of course, that's balanced by warm and sunny conditions in the high Arctic which actually matters for the ice minimum.

Ken Feldman

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Re: The 2018 melting season
« Reply #796 on: May 25, 2018, 12:39:21 AM »
Beginning the analysis in 1979 is cherry picking. Why did we stop discussing the decades long increasing trend - leading up to 1979 - in Arctic sea ice extent? Noting that there's been a flat trend here for a decade is simply interesting in the moment. Does it perhaps suggest that we could be ending one cycle and beginning another? Also interesting that the Arctic sea ice volume is rather interesting in the moment.  http://ocean.dmi.dk/arctic/icethickness/thk.uk.php

One can toggle back - I just put May 23, 2008 side by side with yesterday's ice thickness - interesting.

 Graph was in the 1990 IPCC report.

Seems to me that the cherry pick is to go back to the 1990 report.  The most recent IPCC report was published in 2013.  Here is the comparable graphic from the current report:

http://www.climatechange2013.org/images/figures/WGI_AR5_Fig4-3.jpg

There is no "decades long increasing trend" that you refer to.  Interestly, after 1990 (you left all of that data off in your post), the trend is clearly downward.

Shared Humanity

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Re: The 2018 melting season
« Reply #797 on: May 25, 2018, 02:24:27 AM »
Will the rather flat trend for the Sept min sea ice extent of the last decade, continue in 2018?

Very likely.

litesong

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Re: The 2018 melting season
« Reply #798 on: May 25, 2018, 04:34:03 AM »
The horizontal ten-years trend has no statistically significant difference with the decreasing forty-years trend.
Including the information that the solar TSI has been low for 11+ years(including a 3+ year period setting a 100 year record low)., may cause the flat Arctic sea ice trend to BE statistically significant.

Lord M Vader

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Re: The 2018 melting season
« Reply #799 on: May 25, 2018, 09:12:46 AM »
As we now are approaching June it's highly interesting to see if the current high pressure dome is going to remain in place over the Beaufort Sea and adjacent areas. Latest ECMWF 00z op run suggests that the HP will be in charge over the next 10 days. That should continue to bring warm and sunny weather conditions that should give an upshoot to melting momentum. And if that HP stays over Arctic for another 2-3 weeks it should render some serious damage to the sea ice at the Pacific side.

The only thing that would be worse than the current forecast is if we would see a Greenland Blocking High emerge in June. That would be a disaster!

At this moment we should be very grateful that this is 2018 and not 2013 or 2017!