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jdallen

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Re: The 2015 melting season
« Reply #850 on: May 19, 2015, 02:57:52 AM »
It's anomalously anomalous.  ;)

50 years ago, perhaps even 20 years ago, this would be a "7 sigma" event.  Now I think it may be a portent of the future.

Various weather services are posting flood warnings all over Alaska, the Yukon and NWT.  Wish we could get better data from the RU - the area at the western edge of the Kara is almost as anomalous.

Heat's being driven into the arctic from both sides, almost like a noose tightening around a sack, pinching it in the middle.
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Frivolousz21

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Re: The 2015 melting season
« Reply #851 on: May 19, 2015, 03:28:10 AM »
GFS 00Z 2M temps:



Buoy surface temps sometime around 18z to 20z.  Max heating in this part of the arctic is around 0-2Z.

Even so the Buoys show exactly what the models show.






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Re: The 2015 melting season
« Reply #852 on: May 19, 2015, 08:53:52 AM »
Well the latest forecasts still project this to continue out to 7 days and likely beyond. The Beaufort is starting to torch and we'll likely start to see snow melt throughout the days to come no melt ponding yet visible on any of the buoy cameras at least that I've been able to see. 




Obuoy 12 temperature

Frivolousz21

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Re: The 2015 melting season
« Reply #853 on: May 19, 2015, 10:21:17 AM »
00z gfs

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Frivolousz21

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Re: The 2015 melting season
« Reply #854 on: May 19, 2015, 10:56:05 AM »
You can see the extent of the surface melting on these graphics. 






Gfs 9 day forecast:




This is a really weird set up.



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Neven

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Re: The 2015 melting season
« Reply #855 on: May 19, 2015, 11:38:53 AM »
I have posted the first ASI 2015 update over on the blog. Thanks for all the input, everyone.

And as this thread is the most read thread on the ASIF, I'd also like to announce I'll be on a holiday until the end of Melt Pond May. See you again in Junction June.
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Neven

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Re: The 2015 melting season
« Reply #856 on: May 19, 2015, 12:30:32 PM »
Melt ponds have started forming on the Chukchi and Beaufort Seas, according to the ADS sea ice monitor:
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oren

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Re: The 2015 melting season
« Reply #857 on: May 19, 2015, 12:31:44 PM »
See you soon Neven. Enjoy the holiday!

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Re: The 2015 melting season
« Reply #858 on: May 19, 2015, 02:22:46 PM »
Melt ponds have started forming on the Chukchi and Beaufort Seas, according to the ADS sea ice monitor:

And according to Landsat 8 yesterday. More pics at:

http://GreatWhiteCon.info/resources/arctic-sea-ice-images/winter-201415-images/#Beaufort

Have a great holiday Neven! I cannot help but wonder what the Beaufort Sea will look like by the time you get back?
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Re: The 2015 melting season
« Reply #859 on: May 19, 2015, 02:33:06 PM »
The other thing that is apparent to me is that the floes in Beaufort are not 'large floes' but a agglomeration of floes from previous years and are beginning to 'fail' along the fracture lines. It is a kind of Barber-esque 'rotten ice' with floes glued together by FY ice which is obviously beginning to respond to the higher temps in the areas now?

Sadly these 'faults' may well prove an issue if melt water from the floe percolates through the line of least resistance and into the ocean blow leaving high albedo ice above?

That said if these are previous season floes then what kind of condition were they in come re-freeze last year? Are they the type of ice we view from the aloft cam each Sept? If so then the large floes are Sheep in Wolf's clothing and though we may see them as multiyear thick ice they could be swiss cheese ice on its last legs once the FY ice infill melts out?
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Re: The 2015 melting season
« Reply #860 on: May 19, 2015, 02:54:29 PM »

So what's up with 2012 G?  Something weird happened to the air temperature sensor there between the 8th and 10th of Feb that got rid of much of the day-to-day variability and also seems to have kept it colder than expected. It also coincides with a jump in measured barometric pressure that seems pretty unlikely (spiked over 1050 and has been constantly over 1030 for three months).

http://imb.erdc.dren.mil/irid_data/2012G_temp.png

My best guess is that the sensors are buried in snow, either due to drifting at the buoy site, or maybe the sensor itself has fallen off the pole into the surface snow.  That would explain the reduced day-to-day variability, the increased pressure, and also why it's seemingly not measuring the true atmospheric temperature.  The temperatures from the thermistor string seem to be complete gibberish.

Tor Bejnar

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Re: The 2015 melting season
« Reply #861 on: May 19, 2015, 07:12:52 PM »
I recall reading that melt ponds are fairly stable, for when a small crack penetrates an ice floe under a melt pond, the fresh water will freeze upon reaching the cold (-1.7C) sea water (if not before), sealing the crack.
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Re: The 2015 melting season
« Reply #862 on: May 19, 2015, 07:25:52 PM »
DMI modelled temperature map for the Arctic basin at May 19 at 00z shows that the temps are exceeding freeze point in a large parts of Beaufort. Moreover, the temps at (I suppose!) MacKenzie river delta is about 10C... Pretty hot!

http://ocean.dmi.dk/arctic/weather/arcticweather_imagecontainer.php

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Re: The 2015 melting season
« Reply #863 on: May 19, 2015, 08:34:51 PM »
DMI modelled temperature map for the Arctic basin at May 19 at 00z shows that the temps are exceeding freeze point in a large parts of Beaufort. Moreover, the temps at (I suppose!) MacKenzie river delta is about 10C... Pretty hot!

http://ocean.dmi.dk/arctic/weather/arcticweather_imagecontainer.php

//LMV
All the services are reporting a massive influx of heat into the Pacific Arctic.  The temperatures reported by DMI are very much in line with that.
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Re: The 2015 melting season
« Reply #864 on: May 19, 2015, 09:50:39 PM »
12z ECMWF has 850s exceeding -5 C over the entire Arctic Ocean by 168h, which suggests serious snow surface melting and meltpondogenesis (Am I not allowed to make up a word?  ;) )

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Re: The 2015 melting season
« Reply #865 on: May 19, 2015, 10:23:41 PM »
If I understand correctly, this image shows the polar upper low pushed well south into Canada while the upper high from the Yukon ridges due north across the pole. It's a week away, so just a forecast, but...

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Re: The 2015 melting season
« Reply #866 on: May 20, 2015, 12:31:37 AM »
Today's NWS extended discussions for Alaska (Bolded the parts that matter)
Quote
ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
237 PM EDT TUE MAY 19 2015

VALID 12Z SAT MAY 23 2015 - 12Z WED MAY 27 2015

OTHER THAN EARLY INFLUENCES FROM TS DOLPHIN...THE LARGE POSITIVE
ANOMALY OVER NORTHWEST CANADA IS EXPECTED TO PREDOMINANTLY SUPPORT
ABOVE AVERAGE TEMPERATURES AND BELOW NORMAL PRECIPITATION THROUGH
THE PERIOD...WITH THE ASSOCIATED BLOCK AND ACCOMPANYING SOLUTION
SPREAD SUPPORTING SLIGHTLY ABOVE AVERAGE FORECAST CONFIDENCE.


CONCERNING THE DAY-TO-DAY DETAILS...EXCELLENT MODEL AGREEMENT
CONCERNING THE MERGER OF DOLPHIN WITH A LARGER CYCLONE OVER THE
BERING SEA AT THE BEGINNING OF THE PERIOD NOW EXISTS..
.WITH A
BRIEF PERIOD OF WIND AND RAIN ALONG ITS PATH BEFORE DECAYING.  THE
ONE EXCEPTION HOWEVER TO THE AGREEMENT INVOLVES THE 12Z
GFS...WHICH LIES NEAR THE OUTER EDGES OF THE GUIDANCE WITH ITS
MORE WESTWARD LOW TRACK AND DOWNSTREAM UPPER RIDGE OVER NORTHWEST
CANADA.  THEREFORE...THE PREFERENCES GENERALLY CONSIST OF A 3-WAY
BLEND INVOLVING THE 00Z ECMWF ENSEMBLE MEAN/00Z NAEFS BCMEAN/06Z
GEFS MEAN...TO DIVERSIFY THE CORES AND UTILIZE ITS LARGE
ENVELOPE...WITH ABOUT TWO-THIRDS WEIGHTING TOWARD THE HIGHER
RESOLVING ECMWF CORE. 

OTHER THAN THE ABOVE DESCRIBED CONDITIONS ASSOCIATED WITH THE
REMNANTS OF DOLPHIN...THE PATTERN GENERALLY SUPPORTS ABOVE NORMAL
TEMPERATURES AND BELOW NORMAL PRECIPITATION...ESPECIALLY FOR
EASTERN ALASKA...WITH THE COASTAL MAINLAND AND ALEUTIANS RECEIVING
SOME VARIABLE CONDITIONS...INCLUDING SLIGHTLY COOLER TEMPERATURES
AND HIGHER CHANCES FOR RAINFALL.

JAMES
http://www.wpc.ncep.noaa.gov/discussions/hpcdiscussions.php?disc=pmdak

And the lower 48
Quote
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1138 AM EDT TUE MAY 19 2015

VALID 12Z FRI MAY 22 2015 - 12Z TUE MAY 26 2015

...GUIDANCE/UNCERTAINTY ASSESSMENT...

THE WPC MEDIUM-RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM WPC
CONTINUITY DAYS 3-5 FRI-SUN. THIS SOLUTION STILL SEEMS REASONABLE
AND IN GENERAL REMAINS NEAR THE COMPOSITE OF THE FULL SUITE OF
MODEL AND ENSEMBLE SOLUTIONS...BUT PROBABLY CLOSEST TO THE 00 UTC
ECMWF ENSEMBLE MEAN AND YESTERDAYS 12 UTC ECMWF.

A COMPOSITE BLEND OF THE REASONABLY COMPATABLE 06 UTC GEFS MEAN
AND 00 UTC NAEFS/ECMWF ENSEMBLE MEANS WAS USED FOR DAYS 6/7 IN A
PERIOD WITH INCREASING EMBEDDED SMALLER SCALE FEATURE
TIMING/EMPHASIS VARIANCE. HOWEVER...THE OVERALL PATTERN OFFERS
BELOW NORMAL FORECAST SPREAD AND UNCERTAINTY.


...OVERALL PATTERN AND SENSIBLE WEATHER HIGHLIGHTS/THREATS...

THE BLOCK ESPECIALLY AT MID-HIGHER LATITUDES OVER ALASKA AND
CANADA REMAINS IN PLACE. THIS BLOCK HAS BEEN FORTIFIED BY INFUSION
OF THE EXTRATROPICAL EFFECTS OF FORMER WRN PACIFIC TYPHOONS NOUL
AND DOLPHIN INTO THE NRN/NERN PACIFIC FL0W.

http://www.wpc.ncep.noaa.gov/discussions/hpcdiscussions.php?disc=pmdepd
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Re: The 2015 melting season
« Reply #867 on: May 20, 2015, 04:42:45 AM »
meltpondogenesis (Am I not allowed to make up a word?  ;) )
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Re: The 2015 melting season
« Reply #868 on: May 20, 2015, 10:52:03 AM »
Changes near the Colville River delta (just along the Alaskan coast from Prudhoe Bay) from 18th to 19th May:

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Re: The 2015 melting season
« Reply #869 on: May 20, 2015, 12:31:06 PM »
Persistence, and darn good agreement.  It's funny, the 500mb pattern over North America looks so similar to the one that set up and remained steadfast over the winter, just displaced like 1500 miles north...

First attachment 8-10 day H5 anomalies
http://mp1.met.psu.edu/~fxg1/CMCNA_0z/hgtcomp.html

Second attachment is the sea ice forecast from the CFSv2 (stands for Can't Forecast Shit)   ;D
Third is also from the CFS, showing the anomalies.  Seems like it expects little Fram export and persistent Russian ice.
http://origin.cpc.ncep.noaa.gov/products/people/wwang/cfsv2fcst/
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Re: The 2015 melting season
« Reply #870 on: May 20, 2015, 01:49:25 PM »
3 record highs in 3 consecutive days for Barrow, Alaska
Quote
RECORD EVENT REPORT
NATIONAL WEATHER SERVICE BARROW AK
517 PM AKDT TUE MAY 19 2015


...RECORD HIGH TEMPERATURE FOR THIRD DAY IN A ROW AT BARROW....

THE HIGH TEMPERATURE TODAY...MAY 19TH....WAS 46 DEGREES BREAKING THE
OLD RECORD OF 38 DEGREES LAST SET 6 YEARS AGO IN 2009. TODAY IS THE
THIRD DAY IN A ROW WITH RECORD HIGH TEMPERATURES AT BARROW. THE LOW
TEMPERATURE SO FAR FOR THE 19TH IS 33 WHICH TIES THE RECORD HIGH
DAILY MINIMUM FOR THIS DATE ALSO SET IN 2009.

$$
RFL MAY 15
http://www.arh.noaa.gov/textforecasts.php?type=statement
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Re: The 2015 melting season
« Reply #871 on: May 21, 2015, 07:05:43 AM »
So have the weather models backed off on that heat wave spanning much of the central Arctic basin?

Have been watching the Nullschool temperature map...
http://earth.nullschool.net/#current/wind/surface/level/overlay=temp/orthographic=-35.44,93.43,1444

The Beaufort has been above 0 degrees C over the past few days but that hasn't developed much over the past two days. Likewise, there hasn't been much of a high temperature incursion from the Atlantic side.

So interested to see what the weather models are predicting now, if anyone would be nice enough to post that, thanks.

jdallen

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Re: The 2015 melting season
« Reply #872 on: May 21, 2015, 07:17:16 AM »
So have the weather models backed off on that heat wave spanning much of the central Arctic basin?

Have been watching the Nullschool temperature map...
http://earth.nullschool.net/#current/wind/surface/level/overlay=temp/orthographic=-35.44,93.43,1444

The Beaufort has been above 0 degrees C over the past few days but that hasn't developed much over the past two days. Likewise, there hasn't been much of a high temperature incursion from the Atlantic side.

So interested to see what the weather models are predicting now, if anyone would be nice enough to post that, thanks.
Looking out 48 hours or so, it still looks awful bad.  Looking out a full week isn't any better.  If anything, it looks like all the snow has been stripped off of the Siberian coast.

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Re: The 2015 melting season
« Reply #873 on: May 21, 2015, 10:53:49 AM »
So have the weather models backed off on that heat wave spanning much of the central Arctic basin?

Yes, the models have backed down slightly, but only the less reliable longer term forecast I would say (after all it is more that 3 days since the heat looked bound to stay forever). To me the ECMWF looks a bit 2014ish with lots of HP activity in the central basin, but without that much heat intrusion, so it looks a bit strange that GFS is throwing melting temps all over the central basin in the 120h-180h range. I think GFS will back down from that and the melt during the next 2-7 days will mostly be confined to the peripheries, as one would expect to be the case in May.

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Re: The 2015 melting season
« Reply #874 on: May 21, 2015, 11:24:35 AM »
The 00z euro has 3/4th of the basin above 0C after day 6. 


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JayW

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Re: The 2015 melting season
« Reply #875 on: May 21, 2015, 01:24:36 PM »
I think it just takes some time to get melting to take place.  It takes days, if not weeks of above freezing temps for our lakes in Maine to "ice out".  I believe this pattern will have an effect, I think it's cumulative, and patience is key.  The 8-10 day forecasts have been consistent and a quick look at the ECMWF ensembles doesn't dissuade me from thinking that the models are handling the pattern better than average.  That said, I am basing my thoughts on what's going on at 500mb.  Surface temps are very tricky to forecast, especially when you have inversions.  I'm certainly just a novice with this stuff, so grains of salt are likely needed, but I think things are playing out generally as I expected. 

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Re: The 2015 melting season
« Reply #876 on: May 21, 2015, 01:33:36 PM »
I've been spending some time looking at the GFS reanalysis for previous melting seasons. It seems that the surface daily maximum temps in the early part of the season are surprisingly tightly related to both the size and shape of the final September extent. 2007 and 2012 for example both had above-freezing temps widespread and deeply intruding the central Arctic and all sectors by about June 8th or so, with the first huge intrusion occurring by June 5th. 2013 and 2014 were delayed in reaching this mark, and this seems to have led to the higher September extents.

This year, these milestones seem to be yesterday (May 20) and six days from today (May 27), respectively.

In 2012 there was a brief warm spell on May 22nd and again on May 27th, but these were short lived and the cold returned.

This year, it looks like the cold is gone for good, until the end of Summer.

Absent a severe, prompt, and extended about-face on the part of Mother Nature, we are well on our way to completely destroying the record low in 2012.

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Re: The 2015 melting season
« Reply #877 on: May 21, 2015, 01:45:02 PM »
I think it just takes some time to get melting to take place.  It takes days, if not weeks of above freezing temps for our lakes in Maine to "ice out".  I believe this pattern will have an effect, I think it's cumulative, and patience is key. 

But once the snow is sufficiently water-logged to reduce the albedo substantially, the melting self-accelerates even when meteorological conditions change.

You probably see this in Maine too, I would venture to say. If you have 3 days in a row early in the season (late March?) with high temps in the 60s or even 70s, so that the snow seriously goes into melting mode and the ice surface gets covered by visible meltwater, the season will have an early ice-out, even if the next week is snowy and cold.

This effect is even more extreme in the Arctic, because the timing of the snowmelt occurs when insolation is higher than anywhere else on Earth - equator included, thus enhancing the snow albedo effect. By contrast, what you see in Maine occurs near the vernal equinox or shortly thereafter, with more modest amounts of insolation.


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Re: The 2015 melting season
« Reply #878 on: May 21, 2015, 06:08:16 PM »
In context with the current discussion, these two images may be relevant - comparison of the current snow cover with that in 2012.

The implications for albedo, and by extension, solar capture are significant.
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Re: The 2015 melting season
« Reply #879 on: May 21, 2015, 06:26:12 PM »
As was observed during this time over the last 3 years running, the jet stream has produced a magical blocking pattern that stretches from near the equator and up through the top of Alaska

http://earth.nullschool.net/#2015/05/21/1800Z/wind/isobaric/250hPa/equirectangular=-142.37,48.31,519

the impacts to the arctic from this are also consistent with previous years.  Significant increases in relative humidity and cold, dark cloudy/hazy and precipitation (snow) assist the preservation of sea ice.

http://earth.nullschool.net/#2015/05/21/1800Z/wind/isobaric/1000hPa/overlay=relative_humidity/equirectangular=-149.88,69.80,1306

the observed effects from today's camera

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Re: The 2015 melting season
« Reply #880 on: May 21, 2015, 06:32:53 PM »
Cross posting from the metrics thread, currently NSIDC (1 & 5 day), JAXA and DMI(30%) extents are all at the lowest value for the date since their respective records began.
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Re: The 2015 melting season
« Reply #881 on: May 21, 2015, 06:40:09 PM »
the impacts to the arctic from this are also consistent with previous years.  Significant increases in relative humidity and cold, dark cloudy/hazy and precipitation (snow) assist the preservation of sea ice.

You are a bit messing something up here. In this early time of the year the cloud cover does not have a straightforward impact on the ice: The albedo in the visible is anyway near 1, so the central question is rather how much downwelling longwave radiation you have over the well-covered portions. In addition the past days had clear skies exactly over the ice-free regions in the Amundsen and Alaska mainland.

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Re: The 2015 melting season
« Reply #882 on: May 21, 2015, 06:50:29 PM »
the impacts to the arctic from this are also consistent with previous years.  Significant increases in relative humidity and cold, dark cloudy/hazy and precipitation (snow) assist the preservation of sea ice.

You are a bit messing something up here. In this early time of the year the cloud cover does not have a straightforward impact on the ice: The albedo in the visible is anyway near 1, so the central question is rather how much downwelling longwave radiation you have over the well-covered portions. In addition the past days had clear skies exactly over the ice-free regions in the Amundsen and Alaska mainland.
I tend to agree with Jai here - it's pretty much what we saw in 2013 and 2014.  Down-welling longwave radiation does have a significant effect, but the direct impact of insolation is reduced massively.

That said, quantity has its own quality.  With that moisture, we get heat, and while direct thermal transfer of heat from atmosphere to ice is a small fraction of what is delivered by sea water, in sufficient persistent quantity, it will make a difference.

We've also been seeing a lot of rainfall over the pack in the Chukchi and Beaufort.  This is a departure from 2013/2014, and it reflects the fact that unlike those years, where the sources of the moisture frequently were local, this time we're looking at it being imported directly from the tropics.  QED, the fog and cloudiness are less heat leaving the local ocean, and much more heat being imported into the region from further south.

That's part of what I'm speaking to with the posting of the snow cover maps.  I think the positive feedbacks to increase heat being input in the Arctic are starting to stack up so significantly the negative ones won't be able to hold back the heat.  The climate no longer has enough fingers to stick into the holes in the dike.
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Re: The 2015 melting season
« Reply #883 on: May 21, 2015, 07:00:06 PM »
It seems very clear to me that albedo-driven melt effects of meltponds in early June is the most significant factor of Sea Ice loss.  But that is just me.  I absolutely disagree that insolation is a weaker effect at this time in this region.

On this date today, the insolation off this region is higher than that found in north Florida, the Canary Islands or New Delhi, India

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folke_kelm

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Re: The 2015 melting season
« Reply #884 on: May 21, 2015, 07:02:34 PM »
"The climate no longer has enough fingers to stick into the holes in the dike."
Like Scrat in Ice Age 3?

jdallen

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Re: The 2015 melting season
« Reply #885 on: May 21, 2015, 08:01:55 PM »
It seems very clear to me that albedo-driven melt effects of meltponds in early June is the most significant factor of Sea Ice loss.  But that is just me.  I absolutely disagree that insolation is a weaker effect at this time in this region.

On this date today, the insolation off this region is higher than that found in north Florida, the Canary Islands or New Delhi, India


Oh, don't mistake me Jai (if I was the target of your comment) - I completely agree with you - insolation is stronger rather than weaker now.

I'm still not fully on board with you regarding melt ponds.  A top 5 factor, but not sure *the* top factor.  Not sure what *is* the top factor yet, either.
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cesium62

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Re: The 2015 melting season
« Reply #886 on: May 21, 2015, 08:15:59 PM »
It seems very clear to me that albedo-driven melt effects of meltponds in early June is the most significant factor of Sea Ice loss.  But that is just me.  I absolutely disagree that insolation is a weaker effect at this time in this region.

On this date today, the insolation off this region is higher than that found in north Florida, the Canary Islands or New Delhi, India

Oh, don't mistake me Jai (if I was the target of your comment) - I completely agree with you - insolation is stronger rather than weaker now.

I'm still not fully on board with you regarding melt ponds.  A top 5 factor, but not sure *the* top factor.  Not sure what *is* the top factor yet, either.

2012 suggests that a late season cyclone chewing through the remnants of the ice may be important.  Strong warm winds from the south would seem likely to help.  Rough water on the periphery of the ice from long fetches would also seem a candidate for removing ice.  Water currents up from the Atlantic and through the Bering Strait might be most significant.

One thing we can observe is that the insolation on top of the northern Archipelago mimics the insolation at other locations, but the archipelago ice is more persistent than those other locations.  Archipelago ice is sitting on sub-zero temperature land, suggesting that water temperature  is important, but whether by currents or by absorption of the insolation is beyond my ken.  Melt ponds don't seem to explain the persistence of Archipelago ice.

jai mitchell

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Re: The 2015 melting season
« Reply #887 on: May 21, 2015, 08:31:03 PM »
I was simply clarifying that insolation is massive right now.  This is a primary component of my ECS critique of potential early sea ice and arctic amplification feedbacks on consequences threads.

I know you understand this!   ;D

I know there are other factors, what really got me thinking was the rate of surface ice melt observed by one of the obuoys in 2013 when it was covered by a 2 week meltpond but lost a full foot of surface ice during that period.  This was (I believe) in late july.  So the insolation values are similar to what we would experience today if it was clear and there was snowmelt/meltpond formation.

but there are competing theories to be sure  8)
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jdallen

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Re: The 2015 melting season
« Reply #888 on: May 21, 2015, 09:11:49 PM »
Time to trot this out again.  An excellent and old paper by someone trying to model, understand and quantify the effect of water temperature on ice melt.  Jai, the temps here would apply to your melt ponds, as the approximation for sea water should apply to the heating in the melt ponds, which could become quite a bit warmer than the ice they are sitting on.  Two weeks of melt pond water at ~3C would be about right for your observation.

http://www.igsoc.org:8080/annals/1/igs_annals_vol01_year1980_pg119-122.pdf

The gist of the article can be summarized by this equation:

approximate sea ice melt rate (cm/day) =

.018 * ( H2O temp + 1.8 ) raised to the 1.5th power

A quick table (check my math... I could have munged the computations):

Water TempMelt rate/CM/Day
-1.50.03
-10.13
-0.50.27
00.43
0.50.63
10.84
1.51.08
21.33
2.51.61
31.89
3.52.20
42.51
4.52.85
53.19
5.53.55
63.92
   
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Greenbelt

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Re: The 2015 melting season
« Reply #889 on: May 21, 2015, 09:28:46 PM »
Latest EC forecast looks pretty warm from the Pacific to the pole in the 5+ day time frame.

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Re: The 2015 melting season
« Reply #890 on: May 21, 2015, 09:29:35 PM »
In context with the current discussion, these two images may be relevant - comparison of the current snow cover with that in 2012.

The implications for albedo, and by extension, solar capture are significant.

You are comparing apples to oranges - a GFS map compared to a CFSv2 map. The latter is much more aggressive than the former when it comes to snowmelt, so this comparison really says virtually nothing.

You should compare GFS to GFS and CFSv2 to CFSv2.

plinius

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Re: The 2015 melting season
« Reply #891 on: May 21, 2015, 10:53:29 PM »
Well, I prefer to look at the numbers instead of doing wild theories.

http://www.the-cryosphere.net/8/2219/2014/tc-8-2219-2014.pdf

Fig. 3 shows you that solar insolation does VERY little in April and May. That's because ice is covered with snow at albedo values of 0.8-0.9, probably rather close to 0.9. Hence your 300 Watts/m^2 diminish to a miniscule 30W/m^2.
Transmitted solar heat input into the layer beneath is then quite exactly 0, until at least the snow is gone.
A ten degree difference on top gives you of order 50Watts/m^2, just for comparison...

Csnavywx

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Re: The 2015 melting season
« Reply #892 on: May 21, 2015, 10:59:54 PM »
12Z ECMWF went nuclear after D4 over the Pacific side.

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Re: The 2015 melting season
« Reply #893 on: May 21, 2015, 11:02:42 PM »
Solar insolation does VERY little in April and May. That's because ice is covered with snow at albedo values of 0.8-0.9, probably rather close to 0.9

You have seen the satellite images of melt ponds in May this year I take it?
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jai mitchell

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Re: The 2015 melting season
« Reply #894 on: May 21, 2015, 11:22:07 PM »
Well, I prefer to look at the numbers instead of doing wild theories.

http://www.the-cryosphere.net/8/2219/2014/tc-8-2219-2014.pdf

Fig. 3 shows you that solar insolation does VERY little in April and May. That's because ice is covered with snow at albedo values of 0.8-0.9, probably rather close to 0.9. Hence your 300 Watts/m^2 diminish to a miniscule 30W/m^2.
Transmitted solar heat input into the layer beneath is then quite exactly 0, until at least the snow is gone.
A ten degree difference on top gives you of order 50Watts/m^2, just for comparison...

In your paper the Early Melt Onset (EMO) is the initiation of "wet snow" which is a precursor for melt pond formation and the time when the surface becomes "optically deep" causing more snow melt.  However,  the melt of snow has little effect on sea ice" not until melt pond formation during Melt Onset (MO) is the ice impacted significantly.

In your paper, during 2011 this did not occur until May 30.

Quote
This increase in solar irradiance was linked to the beginning of the melt phase (mean MO on 30 May 2011) and the associated rapid snow melt

I believe this is consistent with my previous statement:

Quote
It seems very clear to me that albedo-driven melt effects of meltponds in early June is the most significant factor of Sea Ice loss

so what, exactly, do you think it "wild" about my theory?

 ???

Addendum,
your assertion that the presence of snow is a strong analog to ice albedo is not quite right.  Snowmelt fractions determine albedo in the mixed-state phase.  Extremely wet snow is nearly as absorptive as melt ponds, with admittedly little impact on sea ice as your paper shows, the impact on sea ice comes later as the snow melt is accelerated under clear sky insolation and hampered by dark cloudy and (and snowy!) conditions that increased precipitable water brings.

note 400% increase in TPW over Chukchi Seas today

http://earth.nullschool.net/#2015/05/21/1800Z/wind/isobaric/1000hPa/overlay=total_precipitable_water/equirectangular=-149.88,69.80,1306



« Last Edit: May 21, 2015, 11:52:27 PM by jai mitchell »
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jdallen

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Re: The 2015 melting season
« Reply #895 on: May 21, 2015, 11:36:30 PM »
In context with the current discussion, these two images may be relevant - comparison of the current snow cover with that in 2012.

The implications for albedo, and by extension, solar capture are significant.

You are comparing apples to oranges - a GFS map compared to a CFSv2 map. The latter is much more aggressive than the former when it comes to snowmelt, so this comparison really says virtually nothing.

You should compare GFS to GFS and CFSv2 to CFSv2.
Thank you for the criticism; How might I find the correct items?  I expect my comparison will still bear out my argument.  I will do some digging as well.
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Csnavywx

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Re: The 2015 melting season
« Reply #896 on: May 21, 2015, 11:57:45 PM »
0.8-0.9 only works for fresh snow (<2 days old). Antarctica holds albedo factors over 0.8 due to relatively pristine airmasses and extreme cold.

This isn't really applicable to a pack that's been hit by a day or two of solid warm air advection. The initial push of WAA and skin/surface melting drops albedo quite fast.

sedziobs

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Re: The 2015 melting season
« Reply #897 on: May 22, 2015, 12:48:56 AM »
According to the images posted earlier today by jdallen, there is virtually no snow across the Beaufort and Chukchi.  Whether actually free of snow or covered in melting snow, these regions would have an albedo of 0.3 to 0.4.

Nightvid Cole

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Re: The 2015 melting season
« Reply #898 on: May 22, 2015, 02:03:33 AM »
In context with the current discussion, these two images may be relevant - comparison of the current snow cover with that in 2012.

The implications for albedo, and by extension, solar capture are significant.

You are comparing apples to oranges - a GFS map compared to a CFSv2 map. The latter is much more aggressive than the former when it comes to snowmelt, so this comparison really says virtually nothing.

You should compare GFS to GFS and CFSv2 to CFSv2.
Thank you for the criticism; How might I find the correct items?  I expect my comparison will still bear out my argument.  I will do some digging as well.

I wish I knew where to find them. For now it remains elusive.

You can of course use a daily mean surface air temperature > 0C as a proxy for surface melt and look at NCEP/NCAR reanalysis.




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Re: The 2015 melting season
« Reply #899 on: May 22, 2015, 05:56:19 AM »
...http://earth.nullschool.net/#2015/05/21/1800Z/wind/isobaric/1000hPa/overlay=total_precipitable_water/equirectangular=-149.88,69.80,1306
You seem knowledgeable on these marvellous nullschool maps.

If you would be so kind as to help me out, is this "total precipitable water" overlay the best one for estimating cloud cover vs if the sun is shining on the ice? For example:
http://earth.nullschool.net/#current/wind/surface/level/overlay=total_precipitable_water/orthographic=-35.44,93.43,1444

(I looked at http://earth.nullschool.net/about.html and also tried "total_cloud_water" as an overlay but it didn't work.)

Also want to know if it is raining/snowing.
So "temp" overlay would suggest rain rather than snow for T~>0?
And then the "relative_humidity" overlay would need to be close to 100%? But then how to distinguish rain from fog?

Any tips would be appreciated, thanks.