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Messages - Rod

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Arctic sea ice / Re: The 2019 melting season
« on: July 23, 2019, 10:19:44 PM »
A while back we had a section where various thoughts were presented on the dark ice bands in the ESS and elsewhere. A few competing ideas were presented with no conclusions, but the white in this image is probably more intact flows of ice with a bit greater thickness than the surrounding rubble.

The dark ice may have active algae growth, sea floor sediment, river sediment, particulate deposits from smoke, or simply be thin enough/fragmented enough to be absorbing more light/passing it through to the ocean below.

The sediment above would have been integrated into the ice either by wave action while it formed in shallow water, or picked up when the ice froze to the river delta/ocean floor.

Fundamentally, there are a lot of ways to make ice dark. There are considerably fewer ways to make ice white. More or less, it comes down to two options: relics of older ice embedded in a weaker matrix (such that they retain albedo while the surrounding material goes to slush) or the weathered remains of pressure ridges (for much the same reason). Or both.

The pattern of fairly small linear features in that ice near the New Siberian Islands suggests the latter.

Since we're on the topic... Pressure ridges are an extremely important aspect of Arctic sea ice, but don't get much discussion here because the large-scale models gloss over them. Basically, where floes are forced together by currents or winds, the ice shatters into blocks. Some of these blocks are pushed upward, in a small-scale equivalent of orogeny, to form visible ridges that can peak several meters above the floes' "ground level". But more importantly in many regards, this process also forces ice blocks below sea level, somewhat akin to the keel of an iceberg writ large. Leppäranta (2005) argued that these pressure ridges, in total, amounted for about half of ASI volume. We can quibble about that number, but the ridging process unquestionably provides for hidden stores of ice.

Also, these large pressure-ridge keels help to stabilize the pack against wind and current. The apparent cryosphere-scale rotation strongly suggests that there has been widespread erosion of this hidden volume store. In areas where sea ice abuts fast ice, the shallow water depth can allow pressure ridges to actually anchor to the sea floor. These structures are called stamukha; I suspect that the persistence of stamukha immediately north of the Sverdrup Islands is what has protected the Prince Gustav Adolf Sea and nearby channels from melt ... but that the shearing off of the sea ice from these anchors is what as allowed the CAA/CAB crack to torque open.

It's hard to back up any of my suspicions about pressure ridge keel behavior because these structures, despite historically being huge volume reserves, are individually too small-scale to be easily identified in the pack, and certainly too small-scale to be represented by most models. I suspect that, system-wide, most of that hidden volume is now gone, and the self-evident increases in motility and dispersion are the consequence.

Lots of melting today, July 20.
I played around with the color balance to try to make this look more natural.

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.
thanks to A-Team for helpful hints, some of which need further work,2558.msg205561.html#msg205561

Arctic sea ice / Re: The 2019 melting season
« on: June 07, 2019, 02:08:20 AM »
    A friend and colleague who is a PhD climate scientist, and whose work is regularly cited in this forum ... (but I'll leave his name out of it, even though Sean said it was OK to cite him... ooops)

    ....and who has watched Arctic weather for many years, brought the subject up at the end of a day-job phone conversation earlier this week.  He said it's hair raising, that he's never seen anything like what (as of Tue. June 4), was forecast for the next 10 days, esp. the latter part of that forecast as we head into mid-June.  One that I was not previously aware of was the amount of precipitable water in the air masses flowing into the Arctic.  e.g.

  And the story is not limited to the Arctic sea ice.

    One striking example as he walked me through a hall of horrors of forecast images was an image of the infamous ~97% Greenland surface-melt day (edit: days in July & August 2012.  The one that was so bizarre that NASA seriously thought the satellite sensor must have gone bad because such a reading was unprecedented and unfathomable.  (And which my friend on the phone said GFS foresaw at least a week in advance, just to defend the underloved GFS a bit.  BTW - GFS is getting the FV3 upgrade June 24!). 

     Then he took me to the 10-day 10th day Greenland surface temp image for this JUNE   And while not covering the almost the entire GIS as happened in the 2012 blasts, the 2019 forecast image was for a 10-day average, not a single day, and the 2019 image was for mid-June, not July or August.

    Another striking image was the projected very early 2019 timing for loss of ice/snow cover north of Greenland.

    While I'm a long time climate hawk and ASIB watcher, not being a climate scientist and being only a recent ASIF lurker with a post count even smaller then Trump's tiny little extremities (I'm talking about his hands, jeesh, get your mind out of the gutter!), it's been difficult for me to interpret the "contextual significance" for all the recent hubub about the 2019 melt season. 

     So for others of you watching the discussion from that perspective, the point of this post is that a PhD climate scientist with expertise and experience in Arctic weather (while acknowledging that forecasts can change, that June is not the whole summer, and that the Arctic is fickle) is having his own "Holy Cow" moments this week, to put it politely.  Stay tuned.  And vote climate. 

Science / Re: Comparison: forcings from CO2, CH4, N2O
« on: September 03, 2018, 03:47:39 AM »
I very much enjoy seeing your opinions AbruptSLR.  Please don't stop posting them. 

...snip …

The first thing I always want to know about an expert is his/her formal education.


Thank you for your thoughtful words.  Good judgement requires hard work to develop and constant effort to maintain.

Personally, I have been impressed by James Hansen's good judgement; and hopefully policymakers will take his advice to heart before it is too late to avoid too severe of consequences.

In this vain of thought I remain readers that AR5 Chapter 8 advises policymakers that the radiative forcing, RF, attributed to methane emissions is more than twice the RF attributed to increases in methane concentration:

Extract from AR5: "The RF attributed to methane emissions is very likely to be much larger (~1.0 W m–2) than that attributed to methane concentration increases (~0.5 W m–2) as concentration changes result from the partially offsetting impact of emissions of multiple species and subsequent chemical reactions."

Edit, for your information I have a  BS, MEng & PhD all from UC Berkeley.

Arctic sea ice / Re: Arctic Image of the Day
« on: August 30, 2018, 04:11:09 AM »
Just to clarify, I am happy you deconstructed the wrong claim of a collapsed ice shelf, I am unhappy with the high and mighty tone you used.

Arctic sea ice / Re: Arctic Image of the Day
« on: August 28, 2018, 02:55:21 PM »
I made the original observation, based on a very clear image, I have been observing this shelf regularly for some 10 years. No I can’t go out and walk on it to verify. But still looks to me that it is in some sort of disintegrating shape. Certainly worst I have seen, time will tell if bits float away. But never intended as fake news or anything similar. It was intended to make people aware and get discussion going, for if this is the case it’s a very significant even. It does need the observation and experience to come to a balance of judgement from an esteemed group like this.

Consequences / Re: 2018 ENSO
« on: August 24, 2018, 04:00:00 AM »
I came across this introduction to el Nino and in particular Modoki el Nino's

The two images below compare temperatures during El Nino events, and during El Nino Modoki events. Notice how the extremes are stronger (darker blue means colder) during the Modoki type events. The first thing you may notice is that the Western U.S. is much warmer and drier in a Modoki event than in a regular El Nino.

The opposite is true over the Eastern U.S., with cooler and wetter conditions than normal and cooler and wetter than a regular El Nino.

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