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Messages - iceman

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1
Arctic sea ice / Re: The 2019 melting season
« on: September 14, 2019, 01:09:52 PM »
A "low bandwidth" animation of Arctic sea ice age since the 2015 minimum:




2
Arctic sea ice / Re: The 2019 melting season
« on: September 04, 2019, 09:40:55 PM »
I've been watching Lingling and Dorian recently, and I'm interested that they both undergo extratropical transition and integrate their momentum into the jet stream around the same time:



Dorian and Lingling are the symmetrically opposite 968mb lows here. Their angular momentum seems to enhance a dipole pattern, and the timing of their momentum transfer will be critical to how it sets up here. Regardless of the exact configuration, it looks like this will split the initiating tropospheric polar vortex into two lobes and allow a major heat/moisture intrusion from the Pacific



As we enter peak hurricane season, it's important to remember that one of the major heat engines that moves heat from equator to pole are tropical cyclones, so watching their activity will be critical to see how the freezing season initiates (or fails to)

This to me indicates that the melting season is not over yet and way may see losses for the next two weeks. I would be stunned if the AO does not go negative again in the next two weeks, but then again I'm just a naive observer and not a pro meteorologist.

Edit: And after looking at this month's PIOMAS, I really wonder if this will push the Sept 15 update into first place.

3
Arctic sea ice / Re: The 2019 melting season
« on: August 04, 2019, 01:15:41 AM »
The cyclone spinning in the Beaufort over the last few days appeared to sit over a lens of warm water at depth. Wonder if Ekman pumping could have brought any of that heat to the surface?

Warming of the interior Arctic Ocean linked to sea ice losses at the basin margins, Aug, 2018
https://advances.sciencemag.org/content/4/8/eaat6773


Maps of heat content in the BG warm halocline. Beaufort Lens

4
Arctic sea ice / Re: 2019 sea ice area and extent data
« on: July 29, 2019, 09:35:55 AM »
Attached is a graph showing cumulative losses from August 1st to the minimum.

Despite starting with a lower extent each decade, the area lost is increasing each decade.  2012 shows up as a real outlier with the difference between 2nd placed 2016 (2.30M) and 2012 (2.90M) almost  matching the difference between 2016  and the 1980's average (1.58 M).

Note that  2008 lost 2.46M so 2016 is actually third, but I'd left  the noughties out  of the graph.

5
Arctic sea ice / Re: The 2019 melting season
« on: July 29, 2019, 04:48:22 AM »
CAA - There is cracking in the landfast ice all the way to the CAB. That's early, but not unprecedented. As near as I can, visibility permitting, the same event happend on these dates in the recent past:

2018 Aug 15
2017 Aug 22
2016 Between July 30 and Aug 04 (thick cloud)
2015 Jul 31
2014 Sept 12
2013 between Aug 11 and Aug 22 (thick cloud)
2012 July 28

6
Arctic sea ice / Re: The 2019 melting season
« on: July 25, 2019, 04:38:16 PM »
First time this month we have 2012 ASI Image for the date. Here is 2007/2012/2016/2019 comparison. I shifted the day since 12 and 16 are leap years.


7
Arctic sea ice / Re: The 2019 melting season
« on: July 23, 2019, 09:11:25 PM »
Insolation at 90 degrees is greater than at the Equator until the first week in August.

Ought to settle this question.
Except that the albedo of the underlying surface is in large part a function of the angle of incidence of the solar radiation. This is true not just for water but also for sea ice.


Source: Hudson, 2011 https://doi.org/10.1029/2011JD015804

At 90°N latitude at this time of year the solar zenith angle is about 70° so that all the time is spent in the high-albedo part of the curve. South of 30°N, once the sun rises, almost all daylight hours have a solar zenith angle less than 70° and for much of the day less it's than 40°; at tropical latitudes it can obviously reach 0° at high noon. The end result is a great deal of time is spent in the low-albedo part of the curve.

I have no idea how to quantify this difference. My point is that it's not as simple as calculating the theoretical 24-hour solar insolation based on latitude alone and calling it a day.

8
Arctic sea ice / Re: The 2019 melting season
« on: July 23, 2019, 01:55:57 AM »
The Kara/Northern Beaufort dipole is bad for the ice. The actual melt processes can be very complex especially at this time of year and the last few posts have highlighted various elements at play.

We've got sun/ocean/rain/snow/ice all at play. But it is far too simplistic to look at just one measure (such as 850hPa temperatures) and infer that subsidence will melt the ice. That's not how it works.

The ESRL expermiental sea ice pages drill down far more detail. It takes considerable time to tease through and assimilate the wealth of forecasts on that page.

I've had a look through their forecasts on precipitation, top melt, bottom melt and albedo changes over the next 5 or 6 days.

First image below is the top melt at +42. At this time the low over the Laptev increases top melt with wind and most likely, rain.

Next image is of top melt at +126. Now we see a line of considerable top melt spreading up through the centre of the Arctic.

This area of top melt appears just after a belt of precipitation passes through, presumably rain/sleet. This is the boundary between the dipole. A classic frontal zone.

The ice under the centre of the high is showing very little or no top melt.

Meanwhile underneath, bottom melt is slower to change but is slowly spreading into the centre as the arctic ocean is still warming and will be probably for another 2 months. Bottom melt increases especially when onshore (to the ice edge) winds drive the warming open water currents under the ice. Persistent winds attack the Beaufort edge and bottom melt peaks there at about +132 (next image). Later in the forecast winds swing back more northerly in that region as the high moves over towards the centre of the Arctic and bottom melt decreases. 

https://www.esrl.noaa.gov/psd/forecasts/seaice/
 

 

9
Arctic sea ice / Re: The 2019 melting season
« on: July 22, 2019, 11:42:33 PM »
I will update the analysis when June 2019 data from MERRA will be available in late July -when nobody will no longer care as sea ice extent will be many thousands squared kilometers below 2012 and the crash will be beyond obvious XD -. Perhaps MERRA datas are going to show a little miracle, against the reanalysis, but is not really likely.

So without any surprise, MERRA2 data backup NCEP/NCAR reanalysis and confirm that the Arctic suck up energy at an impressive pace in June. The first graph updates the scatter plot of September sea ice extent by the NSIDC, versus the June surface net downward solar flux (with a reverse scale on the left, in blue). As forecasted, Arctic (northward of 70°N) surface solar flux reached 120 W/m², a new record. The second and third graph are a quick comparison of accumulated heat in 2019, 2016, and 2012. And last, the map for June 2019, showing the strong signal in Beaufort, Chukchi and Laptev.

This heat will probably have long lasting consequences. It can be noted that the halocline is showing signs of disruption, even in the Beaufort sea :

https://www.whoi.edu/page.do?pid=163197

And in the Chukchi sea, the warmth is even more impressive and is mixing to great depth (up to 100 meters), with major disruption of the halocline probably going on.

In the immediate future, the strong dipole (with a forecasted 50kt jet at 850 hPa ! https://www.tropicaltidbits.com/analysis/models/gfs/2019072212/gfs_mslp_uv850_namer_17.png )  is probably going to help mixing, and hence melting in connection with the warm sea.

P.S. : From a more aesthetic view of the weather, it can be noted that a shallow low is going to "deepen" (around 1000 hPa) over the northern slopes of Alaska due to interaction of the southerly flow with mountains. This low is going to accelerate the flow, with a funneling effect along the coast. Independently from the mentioned jet over Arctic, a strong gale is going to develop over Beaufort and Chukchi sea. Given the situation, mean wind of up to 40 kt at surface seems almost reasonable, but given that the wind is going to blow over open sea this can become quite an event. https://www.tropicaltidbits.com/analysis/models/gfs/2019072212/gfs_mslp_wind_ak_19.png It does not always need a deep low for winds reaching high values.

10
Arctic sea ice / Re: The 2019 melting season
« on: July 11, 2019, 10:28:17 PM »
You guys are completely overestimating how hard it is for the ice in the cab to melt north of 80 degrees north.

We haven't had that peak Insolation hit the CAB

A new record is unlikely.

Am I misreading one of these two outlooks?


I don't know this isn't like The Great Arctic cyclone but the heat that's in the ice and heat that is around the ice is unprecedented so maybe this week or Vortex will be enough to stir things up to cause some collapse.

2019 is going to come very close to a new record.


11
Arctic sea ice / Re: The 2019 melting season
« on: July 06, 2019, 06:54:21 AM »
Currently it's 21C at the weather station at Niuqsuk Airport, just east of Barrow,  with the dewpoint at 11C, with the breeze blowing straight out onto the sea
Those dewpoints mean the ice will be literally sweating the moisture out of the air even without rainfall, with the attendant transfer of heat.  Same applies to any open water as well, assuming SSTs of around zero.

Windy says that, right now temps are up to 25C on Wrangel Island, with similar maximums each day.

(Like the temperature) the dew point drops once the air gets over the ice(3C at the surface, it rises to 6C at 950hPa and 8C at 925, at the pt indicated), but a large and increasing area will experience dew points of 2-4C in the days(and days) to come.

I've attached bunch of screenshots from Windy to illustrate, of surface dewpoint, temperature and humidity. as well as clouds for daytime on the 8th(ie 2 days out). 3C dewpoint, 4C temp and 98% humidity, which as it turns out is predicted to mark the edge of clouds - a lot of ESS ice will be undrr full sun as well. This is going to be interesting to watch

12
Arctic sea ice / Re: The 2019 melting season
« on: June 24, 2019, 04:05:03 PM »
Arctic wide sea ice area is now lowest for the date in the high resolution AMSR2 record:

http://GreatWhiteCon.info/2019/06/facts-about-the-arctic-in-june-2019/#Jun-23

And if you exclude the peripheral seas the picture is much more stark:

And, as many have mentioned, the distribution of the ice this year is significantly different to previous years, as these NSIDC comparison maps show (comparisons for the June 22 date between 2019 and 2018, 2016 (near record) and 2012.  So there is soooo much uncertainty ahead.

BTW I find these maps to really help with visualizing what is happening to the ice, especially this season and how unusual the situation is.  The comparison tool is really quick and easy to use. 

With the Pacific side so open, and ice pouring into the Atlantic, much may depend on how quickly the rather stubborn ice distribution on the Atlantic side changes in the coming weeks.

Thank you, developers at NSIDC !   http://nsidc.org/arcticseaicenews/sea-ice-comparison-tool/   

13
Arctic sea ice / Re: The 2019 melting season
« on: June 22, 2019, 05:26:54 PM »
Included is a 20 hour loop showing the impressive ridge.  As energy rotates around it, it will go through several anticyclonic wave breaks (evident already).  These often give numerical models difficulty.  As they "break" they generally result in a cyclone downstream, in this case the Beaufort/CAA region.   Again, very hard to predict, and should give anyone pause about buying model runs beyond hour 120, and temper expectations.  Just my two cents.  I'll go back to simple observations of interesting features.

http://rammb-slider.cira.colostate.edu/?sat=jpss&z=1&im=24&ts=1&st=0&et=0&speed=130&motion=loop&map=1&lat=0&opacity%5B0%5D=1&hidden%5B0%5D=0&pause=0&slider=-1&hide_controls=1&mouse_draw=0&follow_feature=0&follow_hide=0&s=rammb-slider&sec=northern_hemisphere&p%5B0%5D=band_m08&x=13964.6669921875&y=16288.22265625

14
Arctic sea ice / Re: The 2019 melting season
« on: June 15, 2019, 12:49:33 AM »
unihamburg amsr2uhh overlaid onto ascat with 100% ice (normally white) set to transparent. The amsr2 overlay is 70% transparent to allow other features of ascat to show through, notably greenland. It also helps to make the 'weather' over open water less distracting.
Similar to last year the wash of warm weather has revealed fractures in the older ice that were not visible previously.
jun1-13
thanks to A-Team for helpful hints, some of which need further work
https://forum.arctic-sea-ice.net/index.php/topic,2558.msg205561.html#msg205561


15
Arctic sea ice / Re: The 2019 melting season
« on: May 26, 2019, 02:27:23 PM »
Dove-tailing with the melt pond and snow cover discussion, here's a couple of screen grabs of the snow cover model from Climate Reanalyzer; the first is today, the second is for June 1st.

The takeaway is, GFS predicts snow cover over the next 6 days will be hammered, seriously.

A lot of that melt - 6-10CM worth - will be on the snowpack in the CAB.


I'm wary of the *raw* GFS data and its handling of snowmelt, especially on the ice.  The GFS is not coupled to sea ice, and also has issues dealing with boundary layer (the part that interacts with earth's surface) temperatures.

First attachment
The plots provided by the NOAA/ESRL Physical Sciences Division, Boulder, CO from their Web site at https://www.esrl.noaa.gov/psd/ , which are forced by the GFS forecast, but with a markedly different result. Note that the upper right panel, "GFS ice area", remains unchanged through the 7 day forecast, as its un-coupled"

Second attachment (Requires a click) is the 10 day sea ice forecast from the ECMWF, available at https://weather.us/model-charts/euro/north-pole-zoom1/ice-ocean-lake/20190605-0000z.html , this is a coupled model.

16
Arctic sea ice / Re: HYCOM vs ASMR2 Imagery
« on: May 26, 2019, 11:54:07 AM »
Bumping this thread to point out that the ACNFS/NOGAPS section of the US Navy's web site seems to have disappeared. However ACNFS/NAVGEM can still be found at:

http://www7320.nrlssc.navy.mil/hycomARC/arctic.html

GOFS 3.0 is at: https://www7320.nrlssc.navy.mil/GLBhycom1-12/POLAR.html

and the current GOFS 3.1 is at: http://www7320.nrlssc.navy.mil/GLBhycomcice1-12/POLAR.html

The GOFS 3.1 reanalysis goes back to 2014.

Comparing MODIS, AMSR2 and GOFS 3.1 for yesterday reveals:





17
Arctic sea ice / Re: The 2019 melting season
« on: May 22, 2019, 03:59:51 AM »
Quote
be cause: can only guestimate area that heads out of the basin but it is a lot
Right. Wind-driven ice motion has been extraordinary this freeze/melt season. By translocating thicker, older ice into zones that will melt out later in the summer, or exporting ice altogether out of the basin via the Fram, Nares and Svalbard-FJL chain plus blocking Kara Sea ice on the import side, wind-driven ice motion may challenge conventional bottom and top melt this year as the leading ice volume loss mechanism.

The first image below shows  on mid-basin Atlantic-side feature drift (boundary between old and new ice) over the the last 195 days using twenty-day contours.

A similar area of ice ahead of the front has been (or will be if wind patterns keeps up) irreversibly displaced out of the basin. This area can be measured, not adjusting for compression or extension, by lifting geo-referenced Ascat images onto Google Earth Pro for its ellipsoidal (WGS84) area and length calculations (2nd image shows the 7.109 million sq km polygon of relevant Arctic Ocean.

Wx predictions are the proverbial drunk looking for her car keys under the street lamp because the light is better there -- winds thousands of meters above the ice are easier to predict than the 0m winds, yet only the latter actually move the ice pack (by coupling to pressure ridges and floe edges rather than flat pan).

You can see this on any given day by comparing ice motion vectors observed by OSISAF/NSIDC to winds GFS or ECMWF are showing, before or after reanalysis (3rd image). Surface currents are negligible (or as oceanographer R Woodward notes, induced by ice keels) outside the intake funnels of the Nares and Fram and inconsistent Bering Strait flows to/from the Chukchi. Note the ice pack has a certain amount of mechanical rigidity, leading to cohesive motion despite a heterogeneous stress field.

The Arctic Ocean is seriously 'under-instrumented', meaning models have never had sufficient calibration or feedback guidance. On the rare instances an instrumented ship has been out there in May (eg N-ICE spring 2015), measurements departed markedly even from nearby land stations like Ny-Ålesund. However nobody ever fixed a weather model or reanalysis based on a basin instrument account.

Help is in sight (with a 2-3 year delay?): this Sept, AWI's Polarstern will drift for a full year on a thick Siberian-side floe (lol !) to collect "direct in-situ observations of the climate processes that couple the atmosphere, ocean, sea ice, bio-geochemistry and ecosystem ... to enhance understanding of the regional and global consequences of Arctic climate change and sea-ice loss and improve weather and climate predictions. https://www.mosaic-expedition.org

This won't be meagre point weather and ice properties because they are going out to a 50 km swath radius on both sides of the drift track. The 4th image shows a hypothetic drift trajectory. They'd have been home early this year whereas in 2017/18 the ship would hardly have moved in the hoped-for direction:

233 days of anti-transpolar drift 2017-2018.mp4
https://forum.arctic-sea-ice.net/index.php/topic,2278.msg155398.html#msg155398

The Oden made a remarkable observation of open water at the north pole on 25 Aug 18, photographing a walrus there, messing with a research sled. Ask yourself how much open water there had to be regionally for a walrus to swim to the NP on that date and when it last ate: the water is 4,087 m deep whereas the deepest walrus dive ever recorded is 500m.

This and a few little things like ice thickness went seriously under-reported (except by Jim Hunt and twitter). This has really got to change -- scientists chewing on their cud for years (buffing their journal articles) while leaving everyone else in the dark.

I had an identical experience trying to get even the most mundane CTD casts from the Polarstern when by great good fortune they were able to reach the Weddell Sea during that unprecedented reversal of the Fram in Feb 18 attributed to a sudden stratospheric warming. A cr*ppy article by another research group ensued who also couldn't get the data. Where is the public benefit in  hoarding?

18
Arctic sea ice / Re: The 2019 melting season
« on: May 15, 2019, 08:24:24 PM »
Minor correction, the water vapour is always in the air absorbing long wave radiation. At the dew point it condenses, and makes mist, that is absorbent to the visible spectra, insulating against short wave radiation.

19
Arctic sea ice / Re: The 2019 melting season
« on: May 14, 2019, 12:15:11 AM »
Yes, Frivolous, this is what I was concerned about 2 weeks ago when the end stratospheric warming went crazy. It set up a pattern of spin down from the stratosphere intensifying blocking patterns in the high north. The strong Scandinavian blocking led to very intense upward wave energy transfer that caused the powerful end warming in the stratosphere. Over the next several months the stratospheric spin down will repeatedly couple with blocks in the troposphere which also rotate clockwise. Upward energy transfer into the stratosphere is over for the summer but downward effects are possible when there's high pressure over the Arctic because the clockwise spins may align. You wrote:

For those who are not aware:


Meteorology speaking this setup is essentially the Holy Grail of having a record-setting Arctic sea ice loss during the summer.

Solar energy right now is booming over the arctic.  The best way to set up things for huge loses of sea ice is sprawling upper level atmospheric ridges of high pressure that exist from top down.

This is the path to dry sinking air and wall to wall sunny skies.

We have never had a May 20-30th GARGANTUAN RIDGE that preconditioned the ice for huge June and July loses.


Stay tuned


Over the weekend I reviewed the stratospheric patterns for summers for the past 20 years and found that the stratospheric end warming conditions increase the odds of the Arctic oscillation being positive or negative - in this case high pressure means negative - but there are many other things going on.

What's starting to happen in May looks like the worst case set up for Arctic ice melt. The figures I looked at showed variability that give me very low confidence in a July forecast based on the end warming patterns by themselves. However, we can use the end stratospheric warming information to evaluate the likelihood that a global model such as the CFS model is making a decent forecast. The CFS model struggles with ocean upwelling, melting snow and ice, and the evolution over time of SSTs, but, based on my experience it may have a good handle on large scale stratospheric tropospheric coupling in the summer.

If it does, were going to witness a new record low in sea ice extent, area and volume this year. The latest CFS runs predict the high pressure and subsidence over the pole and Greenland will persist into July. This CFS model forecast makes sense because of the intense late end season stratospheric warming at the end of April.

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