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Topics - johnm33

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Arctic sea ice / State of the ice
« on: June 27, 2017, 06:49:57 PM »
First a couple of posts from A-team, from melt season ,1859 june 8  1834.1850
The N-ICE2015 papers have arrived, 22 of them. These papers represent six months of precious at-sea observations coordinated with simultaneous overhead remote sensing. While somewhat dated at 30 months, they remain very relevant to this spring’s melt season along the Arctic Ocean periphery north of Svalbard.

The papers are listed here along with their key points and download status: http://onlinelibrary.wiley.com/10.1002/(ISSN)2169-9291/specialsection/NICE1/

Some of these are currently paywalled, others are open source or available from https://sci-hub.cc/ (or TOR scihub22266oqcxt.onion) using the doi. Clicking then on ⇣ сохранить статью downloads the article or final draft as a pdf. It’s not currently known if US copyright law applies to Russia under self-anointed US exceptionalism — or vice versa under a stronger principle of Russian exceptionalism. Unblocked supplemental is available separately at journal sites.

The question is, do we muddle along without anyone reading these papers? Frankly, that’s not sustainable; we’re not here to promulgate anachronistic misinformation. There’s a definite need for fresh air in our near real-time interpretation of satellite ice products for the Svalbard-FJL periphery. Six months data from the ice changes everything.

I tried below with one of these papers to see if it is feasible to concisely summarize full texts, lessons learned without the length. No, it is not.

Mixing rates and vertical heat fluxes north of Svalbard from Arctic winter to spring
aMeyer, I Fer, A Sundfjord, A Peterson
3 June 2017 DOI: 10.1002/2016JC012441
http://onlinelibrary.wiley.com/doi/10.1002/2016JC012441/full

The observations cover the deep Nansen Basin, the Svalbard continental slope, and the shallow Yermak Plateau from January to June 2015. Average winter heat fluxes during quiet times in the ice-covered Nansen Basin are 2 watts per sq meter at the ice-ocean interface, 3 within the orderly density gradient (pycnocline) below the surface mixed layer and 1 below.

These heat fluxes are dwarfed In late spring over the Yermak Plateau by heat fluxes of 300 close to the surface. The forcing factors here are wind, near-surface warm Atlantic Water, steep shelf topography and above all, storms:

    Wind forcing increases turbulent dissipation seven times in the upper 50 m, and doubles heat fluxes at the ice-ocean interface. The presence of warm Atlantic Water close to the surface increases the temperature gradient in the water column, leading to enhanced heat flux rates within the pycnocline. Steep topography consistently enhances dissipation rates by a factor of four and episodically increases heat flux at depth. It is, however, the combination of storms and shallow Atlantic Water that leads to the highest heat flux rates observed: ice-ocean interface heat fluxes average 100 W m−2 during peak events and are associated with rapid basal sea ice melt, reaching 25 cm per day.


That would be 2 meter thick ice gone in 8 days if the storms lasted that long at peak intensity (which they don’t).

In the Arctic, sea ice at the surface reduces the transfer of wind energy to the ocean, causing turbulent dissipation rates to be an order of magnitude smaller than at lower latitudes. Away from boundaries, mixing of the Arctic water column is dominated by much smaller lateral intrusions and double diffusive fluxes of temperature and salinity gradients.

Without the sea ice cover, energy from winds, ocean tides, currents and breaking internal waves interact with topographic features on the sea floor to bring turbulent vertical mixing of previously stable stratifications. That’s especially pronounced over the rough topography of the Yermak Plateau northwest of Svalbard which has twice-daily strong barotropic tides. At its coriolis latitude, extracted energy cannot propagate away as linear internal waves and so dissipates locally, with rates of sufficient magnitude to greatly enhance impacts of Atlantic Water on regional ice cover. This water is normally isolated from sea ice by intervening cold Polar Surface Water stratification.

    The Atlantic Water inflow is the main source of oceanic heat to the Arctic Ocean but little of that heat actually has reached the sea ice in the past, though that is changing with newly thinner ice, a longer season of open water, and more frequent and extreme storms from the south.

    The RV Lance completed four drifts in the Arctic north of Svalbard anchored to different floes, the most favorable drift track (Floe #3) running from April 18th to June 5th. Their profiler instruments measured turbulent heat flux in the upper 300 m of the water column.

    The depth of the upper boundary of Atlantic Water, different from the depth of the 0°C isotherm, was found as shallow as 30 m depth and as deep as 300 m.

    The large heat flux values observed at the 0°C isotherm can be explained by the fact that the 0°C isotherm is a natural boundary between waters from the Arctic at the surface (Polar Surface Waters and warm Polar Surface Waters) and waters with Atlantic origin at intermediate depths (either Modified Atlantic Water or Atlantic Water). These two families of water masses have such distinct temperature characteristics that this boundary has large temperature gradients.

    The heat flux peaks coincided with periods of large basal sea ice melt. A major melt event took place on 16 February [see 10.1002/2016JC012011,10.1002/2016JC012403, 10.1002/2016JC012195] during a large winter storm but no data were recorded due to foul weather and sea ice conditions.

    The largest heat flux estimates during N-ICE2015 were recorded when the proximity to Atlantic Water was combined with storms. This happened three times: on 16 February, 2–5 June, and 11–13 June 2015. During each of these events, a storm took place, ice drift speeds were larger than 0.4 m s−1, and Atlantic Water was present at less than 100 m depth. Heat fluxes at the ice-ocean interface averaged 106 W m−2 during the last event in June. These enhanced heat fluxes lead to the warming of the water below the sea ice, which in turn triggered large basal sea ice melt. A basal melt of 25 cm/d was recorded from 5 June at the end of Floe 3, and again during Floe 4 after 10 June 2015.

    Ice mass balance buoys also observed rapid sea ice melt during the 16 Feb 15 basal melt event and derived conductive heat fluxes estimates that peaked at 400 W m−2 These extremely large basal melt events led to the decay of the ice, making it more vulnerable to swell and waves, and ultimately to break up events.

    The combination of storms and shallow Atlantic Water both in winter and summer induced large ocean heat flux of order 100 W m−2 in the upper ocean associated with massive basal sea ice melt events. This highlights the importance of predicted increased storm frequency in the Arctic that could erode local stratification and tap into warm subsurface Atlantic Water. In winter, this would lead to reduced growth, weakening, and even melting of the sea ice, while in spring such events would accelerate the melting and breakup of the sea ice. The warming and shoaling of the Atlantic Water inflow north of Svalbard and in the Barents Sea combined with increased storm frequency could lead to a significant reduction in sea ice cover further along the Atlantic Water inflow.


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The rest / 2017 open thread
« on: February 17, 2017, 01:50:12 PM »
If it's about the Arctic and 2017 with no obvious home here's where it belongs.
This paper outlines the area l've been thinking about http://www.nature.com/articles/ncomms2505 illustrated here.
http://www.nature.com/articles/ncomms2505/figures/1
 Whenever i thought tides and turbulence were running high in Baffin/Labrador there'd be streamers emerging from the ocean, there must be a more technical name for them but illustrated here. http://go.nasa.gov/2lpzqDm just by Hudson strait last full moon. So now when i see streamers i suspect vortices, this implies that angular momentum is carried through phase transition, is that possible? c+d in fig 4 from the paper illustrate the current across the north barents sea slope, it's my contention that this is a tidally driven current that is increasing as the resistance of the ice in the Arctic weakens. The weakening has two immediate causes the first is the reduction in the amount of kinetic energy needed to forge a path through the ice, that is when there was thick ice the underside caused huge amounts of turbulence dissipating any coherent stream, like a baffle, the second is that the ice has less mass and moves more readily. This second means that given the right/wrong wind conditions the current will be accelerated or slowed by mass ice movement.   The only analogy that springs to mind is where every turn of a roundabout you add a little to the momentum,and when the current reaches some threshold the fractions within it become organised and an overturning c/w current evolves, so as the tidal forcing continues and the resistance fails the current increases and we may have some way to go before both its flow and vorticity peaks.
In the first image below, despite being long after the full moon some streamers are showing, and possibly some ice is being accelerated away from the front. The second shows some streamers a little closer to Svalbard.


Food for thought.

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Greenland and Arctic Circle / Baffin and Labrador seas
« on: April 20, 2016, 06:33:13 PM »
I think we're going to see a lot more action on the west coast of Greenland much of it caused or enhanced by the changes happening in these seas.
The last few days the warm anomoly in Labrador has slowly disappeared, there's been no equivalent halt to the warm water subducting off the east coast.

http://earth.nullschool.net/#current/ocean/surface/currents/overlay=sea_surface_temp_anomaly/orthographic=-52.54,68.76,736/loc=10.186,74.946 click the < to get it to go back a day. This is a detail from http://polar.ncep.noaa.gov/sst/ophi/color_newdisp_anomaly_north_pole_stereo_ophi0.png
 
There have been powerful north winds in Baffin perhaps moving sufficient volume of ice south to cause the Irminger waters, to rise up from the slope and head north. The latest polarview on DMI of Sisimiut shows turbulence which seems to be an indication that the wgsc is on the move, we'll see soon enough.

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Science / Milankovitch cycles
« on: January 07, 2015, 11:06:12 PM »
I keep seeing references to Milankovitch cycles which completely accept the theory, so this is just to air my scepticism without derailing elsewhere. In this, http://www.binaryresearchinstitute.org/bri/research/papers/ComparisonPaper.pdf , I find the better fit of angular momentum distribution particularly persuasive. In this, http://www.binaryresearchinstitute.org/bri/research/findingit/gravprobeb-update.shtml once again data which doesn't fit the paradigm is presumed compromised. When i have time i'll take a look for a link to my preferred theory.

5
Science / More positive feedback
« on: August 25, 2013, 10:43:46 PM »
Brief link on dimethyl sulphide emmissions. http://phys.org/news/2013-08-science-global-source-sea.html

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Arctic sea ice / How many days earlier than 2012
« on: April 04, 2013, 09:59:53 PM »
With monthly polls it may be interesting to compare the rate of change.
For instance on http://www7320.nrlssc.navy.mil/hycomARC/navo/arc_list_arcticictn.html  the cracks across the thick coastal ice disconnecting it from the coast show up on the 21st March [ignoring those which took place before the melt season] whilst last year the first signs were on the 28th July, thats 129 days indicating a very different arctic this year.
 wanderer posted ijis dropping 200k [re arctic sea ice free (extent)] , when did that first happen last year?

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