Glossary ... for newbies and others

[gerontocrat]

CAS = Central Arctic Sea.  Used by NSIDC.  Which gerontocrat tells us is 3.2 km2 less than the CAB.  JAXA uses CAB right?

Whoops - we are talking about the division of the High Arctic into the 7 central seas
- see attached table & maps.

[Steven]

CAS = Central Arctic Sea.  Used by NSIDC.

Where does NSIDC call it "Central Arctic Sea"?  On their website they call it Central Arctic Basin (or briefly Central Arctic), just like everyone else. 

There are different ways to define the CAB (Wipneus uses a different definition than the NSIDC).  But I see no reason to add some non-existent "CAS" terminology that was made up by gerontocrat.  By that logic, you may as well rename Hudson Bay to Hudson Sea...

[Glen Koehler]

   I hear you.  I was just responding to gerontocrat's CAS graphs and trying to clarify "CAS" vs CAB.  But apparently there is no such CAS label, just different definitions for CAB.  So I change that suggestion to a new one -- the glossary should note that CAB has different definitions between NSIDC and others.

[oren]

Gero maybe you can replace CAS with CAB Central Arctic Basin (and Baffin Sea to Baffin Bay) in your publications? This will help clarify things by sticking to the common names.
I will add a clarification to CAB in the glossary regarding its contentious borders.

[Glen Koehler]

   If the ASIF glossary is not limited to acronyms, even though gerontocrat restates the list in his updates, glossary definitions for
Central Arctic Seas (= Chukchi, Beaufort, CAA, East Siberian Sea, Central Arctic Basin, Laptev Sea, Kara Sea)
vs.
Peripheral Arctic Seas (=Okhotsk, Bering, Hudson Bay Baffin  Bay, Gulf of St. Lawernce, Greenland Sea, Barents Sea)
  would be useful to have in the glossary because that is where people are likely to go first when they encounter those terms and are looking for clarification.

    Also worth noting in definition of the CAB that even though the Lincoln Sea is labeled as a separate entity (e.g. NSIDC map), for Extent/Area/Volume stats it is counted as part of the CAB.

[oren]

Added entries for Peripheral Seas and for High Arctic. Edited CAA entry to include list of main waterways. Edited CAB to include mention of the Lincoln Sea - and the Wandel Sea...

[Glen Koehler]

     1st draft glossary entry for "Atlantic Front"  - "An area of what used to be contiguous ice pack between the Fram Strait - Svalbard - Franz Josef Land and the North Pole that fractured into individual floes in 2020-2021."   Feel free to edit.

[Glen Koehler]

     1st draft entry for Transpolar Drift - "The predominant pattern of ice movement in the Arctic Ocean from the Russian side across the North Pole and towards the Fram Strait between Greenland and Svalbard.  The speed and direction vary, but this pattern consistently occurs." 
    I'm sure somebody can do better.

     1st draft entry for Beaufort Gyre - "A loosely defined circular pattern of ice movement from the Beaufrot Sea towards the Russian side of the Arctic Ocean and then toward the Central Arctic Basin and ultimately back to Beaufort Sea.  However, whether such a pattern actually exists is a matter of debate as there is neither a persistent nor consistent specific pattern to the ice movement.  Thus some experts dismiss it as making any number of temporary periods fit under a name that is not really an actual entity.  The concept of a Beaufort Gyre is frequently cited as a source for the creation of multiyear ice because the movement would keep the ice in the regions of the Arctic Ocean for many years allowing ice to accumulate thickness from year to year without exiting the Arctic.  The transition of the areas traversed by a hypothetical Beaufort Gyre into areas of summer ice melt is cited as the reason for the demise of multi-year Arctic sea ice."

     I'm really sure somebody can do better that this.

     I think both terms should be in the glossary so that new people coming to the Forum can get up to speed with the terminology bandied about quickly.

[oren]

Thanks Glen. I will add all these terms to the glossary, but reduce the level of detail to maintain some uniformity. In parallel I have made quite a few edits recently and will continue to somewhat enhance the level of detail in some of the entries.
Also added HYCOM, CDW, AABW, DMI +80N.

[Glen Koehler]

ECS = Equilibrium Climate Sensitivity, increase in average global surface temperature from a doubling of CO2 and decades~century+ for temperatures to stabilize.

[oren]

Added, thanks for your contributions here Glen.

[Glen Koehler]

expanded entries
NOW - North Open Water, aka North Water Polynya.  Largest Arctic polynya (area of year-round open water surrounded by sea ice) between Greenland and Canada in northern Baffin Bay.

OMG - Oceans are Melting Greenland.  5-year NASA mission to understand the role of the ocean in melting Greenland’s glaciers.

More important - Glossary needs entries for Extent, Area, and Volume with regard to what those terms mean when used to describe ASI.
Not disposed to do that right now myself.

[oren]

Will do, thanks.

[KenB]

More important - Glossary needs entries for Extent, Area, and Volume...

And perhaps "concentration" in the ASI-specific sense of "Extent divided by Area"  and it's inverse, "dispersion?"   See, e.g., Gero at:
https://forum.arctic-sea-ice.net/index.php/topic,2975.msg265087.html#msg265087

[Rod]

I believe “compaction” is the term used in these forums for area divided by extent. Gerontocrat created the inverse to represent what he views as “dispersion.”

“Concentration” is determined by the satellites. “Compaction” is an interesting number created in these forums several years ago.  To my knowledge it has never been studied or empirically tested in a scientific journal. Same with the “dispersion” number.

[gerontocrat]

I believe “compaction” is the term used in these forums for extent divided by area.

“Concentration” is determined by the satellites. “Compaction” is an interesting number created in these forums several years ago.  To my knowledge it has never been studied or empirically tested in a scientific journal.

The trouble with using the the word compaction is it implies that when compaction increases the ice is being squashed together, when that may not be happening. It may simply be that widely spaced floes are becoming closer to each other.

Concentration is a better word as it is simply the ratio between area and extent.

I think that compaction is best used to describe a situation where separated ice floes are being squashed together, producing pressure ridges and / or a coherent ice pack / ice sheet structure is emerging.

ps: I started to produce graphs of "dispersion" (extent divided by area) for periods when ice that had been closely compacted started to separate and open water became significant. It seemed also a better way to illustrate how often as minimum approached NSIDC sea ice extent exaggerated the real amount of ice remaining. It also helps to describe how winds forcing sea ice drift can break up a coherent ice pack by dispersion into open water (e.g. the Greenland and  Barents seas).

[Rod]

I had a typo in my original post that I changed while you were in the process of compiling your response. 

I think the important thing is that “concentration” comes from the satellites. On this forum we have made assumptions about that data by dividing area by extent or extent by area to give us clues as to what might be happening.

However, to my knowledge, there is no scientific basis to assume that dividing area or extent gives a real value.

Those numbers should be taken with a grain of salt so to speak.

[oren]

The correct term for extent divided by area is compactness, as defined by Neven years ago, see for example CAPIE in the glossary. Compaction and dispersion are the main phenomena that affect compactness.
Compactness could also be called disperseness, or some other sort of derived ness word.

The opposite is concentration, a well defined term coming off NSIDC measurements.

[oren]

Expanded OMG and NOW, added Polynya, expanded SIC, SIA and SIE, expanded SIT and SIV.

[Rod]

Thank you Oren! 

This is the kind of stuff that takes lots of your time.

We all appreciate your time and devotion to these forums! 

Thank you again, for all of your hard work!

[Glen Koehler]

Ditto, Thanks Oren.

[P-maker]

Since we are entering uncharted territories, we may have to use old words in new meanings, or invent new meanings out of old words.

May I suggest the use of "denseness" and "scantiness" in an attempt to clarify the wording we are discussing.

[oren]

How about diffuseness?

[Steven]

The correct term for extent divided by area is compactness

It's the other way around.  Compactness is sea ice area divided by sea ice extent.  See e.g. https://tc.copernicus.org/articles/12/433/2018, Figure 4.

Or in other words, compactness is the average concentration of sea ice, averaged over all grid points in the Arctic Ocean with a sea ice concentration of at least 15%.

[oren]

Added SWT, a term from Antarctica.

[Glen Koehler]

RE "AMO - Atlantic Multidecadal Oscillation"
     Definition should be updated to add that the guy who originally proposed its existence (Michael Mann) now agrees with critics that have said it is not an actual oscillation but instead was a false artifact of data analysis.

[Glen Koehler]

QEI = Queen Elizabeth Islands.  The northernmost cluster of islands in Canada's Arctic Archipelago: Ellesmere Island, Sverdrup Islands, Parry Islands.

[oren]

Thanks, added.

[Freegrass]

Is Frexport an acceptable new term? As in Fram export? 
They did it with Brexit...

I always wanted to invent a new word... 

[oren]

Sorry, no, and please avoid using it on the main thread as not all readers are at the same level of familiarity.

[Glen Koehler]

  High Arctic = CAB, Beaufort, CAA, Chukchi, ESS, Kara, and Laptev.

 Peripheral Arctic = Baffin, Barents, Bering, Greenland, Hudson, Okhotsk, St. Lawrence

[Tor Bejnar]

When I use High Arctic l mean north of 80N and not including land areas.  In other words, a subset of the CAB.

[oren]

Happy to report that High Arctic and Peripheral Seas were already in.

[Glen Koehler]

    Sorry about that.  I thought I looked and did not see them there.  Oy.

[oren]

No problem. Thanks for your continued help expanding the glossary.

[trm1958]

I have recently purchased (on Kindle) a couple new (2022) books on the Climate Crisis. They refer to this as "Climate Breakdown". Not AGW or "climate change" or such. I have updated my personal text on this and humbly suggest we use this term in future.

[KenB]

CAI - Central Arctic Index

As mentioned by Zhang, et al. in "Arctic sea ice motion change and response to atmospheric forcing
between 1979 and 2019" (https://sci-hub.se/https://doi.org/10.1002/joc.7340)

"Vihma et al. (2012) defined a simple index (Central Arctic Index, CAI) to characterize the
meridional wind forcing that parallels the TDS. The CAI denotes the east–west gradient of
the SLP across the central Arctic Ocean, which is approximately perpendicular to the TDS
(Vihma et al., 2012)."

E.g.:  "We examined the correlation between changes in ice drift speed and in various atmospheric circulation indices, and found that the correlation was highest between ice speed and the CAI, suggesting that the strength of the TDS is of great significance to the sea ice circulation for the entire Arctic basin."

[Glen Koehler]

And the "weighted SMOS" chart, indicating the amount of Arctic sea ice pixels which have escaped surface wetness, as calculated and produced by Steven in https://sites.google.com/view/arctic-sea-ice/home/surface-melt.

Binntho is telling it true, of course. SMOS is a great tool for indicating surface wetness in summer (and thin ice thickness in winter). In fact we have a chart that tracks the number of pixels that are not wet, we had this going on in the past few years thanks to the data wizard Steven.
See my quoted post above, I will post this chart every week during summer when the data is updated. Steven's site now says "No data available since 15 June 2023".

     The need for the  "Don't use SMOS during melt season" corrective keeps recurring.  Perhaps we need a sticky "glossary" for interpretive guidelines for various data products.  Such as:

1.  The "Do NOT use SMOS thickness estimates" during the melt season.

2.  The transitory dark patches in Aluminium's B&W animations (forget the source for those) do NOT mean open water.  It might indicate water vapor in the air above the ice.

3,  Indication in HYCOM images of garlic press movement across the CAB-CAA border is not accurate.  (But why do they look that way?)

4.  The Nico Sun differential Arctic albedo charts assume 100% clear sky which is rarely if ever completely true.

5.  Melt pond draining has a strong and dramatically rapid effect on images that show surface wetness.  e.g. "When the melt ponds drain apparent compaction goes up because the satellite sees ice, not water in ponds." - FOoW

There must be others.

     <<<edit  Oren basically answered the question below with Steven's beige pixel chart.  Is that method confirmed to be accurate?  What is the basis for the weighting?  Differential area per pixel? >>>
      Going back to SMOS.  Those images are worthless as thickness indicators during melt season, but do they convey useful information about the degree of surface wetness during melt season?  If so, as Binntho noted it is pretty interesting to see most of the ASI with some degree of surface melt, and much of it quite strong. 

     That may not be a correct interpretation, but I doubt it, given that I have never actually made a mistake.  I thought I did once, but it turned out later I was wrong. 

[oren]

Great idea, I will edit your list and insert it into the beginning of the glossary when I have time, although not sure those not knowing would actually read it. But in any case it's good to have some official version listing the caveats and known issues of each major tool/data source.

[Glen Koehler]

     Instead of a separate list of caveats, it might be better to add the caveats to the definitions of the different data product acronyms.  E.g. add the SMOS caveat to the SMOS entry in the glossary, HYCOM caveat to the HYCOM entry etc.

[oren]

I'll think of that, when I get to it. Just need time which is quite the rarity these days.

[Glen Koehler]

     The terms "Extent", "Area", "Thickness", and "Concentration" are central to ASIF discussions, but the glossary does not have definitions for those terms.  Here are suggested versions.  They are longer than the other glossary entries.  But given the centrality of these terms, I think the word counts are justified.  If shorter definitions are required, so be it.  Less complete but more concise versions would be better than nothing. 

Extent = area of the Arcitc ocean where at least 15 percent of the surface is frozen. This threshold was chosen because scientists have found that it gives the best approximation of the edge of the ice.
Source: https://www.epa.gov/climate-indicators/climate-change-indicators-arctic-sea-ice#:~:text=Sea%20ice%20extent%20is%20defined,the%20edge%20of%20the%20ice.

Area = area covered by each grid cell by the percentage of sea ice it contains, provided it has at least 15 percent concentration.
    Here is an example using three equal-sized grid cells of satellite observation.  The three cells have ice cover on 5%, 50%, and 100% of their respective area. 
     Area =  0 for the 1st cell (since it is <15%). 
                 0.5 * 1 km2 for the 2nd cell = 0.5
                 1 * 1 km2 for the 3rd cell = 1
                 Total AREA for the 3 cells = 0 + 0.5 + 1 = 1.5 km2
    By contrast, the Extent values for these same cells would be
                 0 for the 1st cell (since it is <15%). 
                 1 * 1 km2 for the 2nd cell = 1 (because 0.5 is >15% it counts as 1 for Extent)
                 1 * 1 km2 for the 3rd cell = 1
                 Total EXTENT for the 3 cells = 0 + 1 + 1 = 2 km2
     Because of the way Exent and Area are defined, Extent is always greater than Area.
     Extent describes the size of the ocean area defined by the perimeter of the Arctic sea ice.
     Area describes the area within that perimeter covered by ice.
Source:  https://nsidc.org/learn/ask-scientist/what-difference-between-sea-ice-area-and-extent#:~:text=Sea%20ice%20area%20is%20the,gives%20higher%20values%20than%20area.

Thickness - Freshly formed sea ice can be as thin as a few sheets of paper or as thick as a one-story house, depending on how long it has existed. Measuring sea ice thickness is harder than measuring how much sea ice covers the ocean surface. No current technology enables scientists to directly and continuously measure sea ice thickness over a broad area. Instead, they use multiple approaches to estimate sea ice thickness: surface measurements, submarine surveys, remote sensing, and computer models.  Every method currently employed to measure sea ice thickness has its limitations, and methods differ in the details.
Source:  https://nsidc.org/learn/ask-scientist/how-thick-is-sea-ice

Concentration - Area divided by Extent.

[oren]

I will write shorter definitions for the glossary top post, and link to your post for further info.
When I have time, and no I haven't forgotten my previous promise upthread. Just swamped.

[KenB]

Hi Oren,
   Someone in the current freezing thread was asking what "Fram export" meant, so maybe an addition here would be good?  Also, in the top post above all the glossary entries, there's a link to "NSIDC's glossary" that resolves to  http://nsidc.org/cgi-bin/words/glossary.pl but that's a 404.  I found their glossary at https://nsidc.org/learn/cryosphere-glossary so maybe we could link to that instead?  Thanks for everything!

[oren]

Thank you KenB, I have updated the broken link.
I have several other corrections needed as well, following Glen's suggestions above and your suggestion as well. I have been busy and distracted and it's only getting worse but eventually I will handle all.

[KenB]

Hi Oren,
   A posting by Niall in the 2024 melting season thread (https://forum.arctic-sea-ice.net/index.php/topic,4176.msg396186.html#msg396186) includes an image and graph with several items that might be useful additions to the glossary:

MOC  -  meridional overturning circulation
AMOC - Atlantic meridional overturning circulation (we already have this)

Sv - In oceanography, the Sverdrup (Sv) is a non-SI metric unit used to measure the volumetric flow rate of ocean currents. One Sv is equal to one million cubic meters per second, or 264,172,052 US gallons per second.

and maybe:

MOCHA - Meridional Overturning Circulation and Heat-flux Array
OSNAP - Overturning in the Subpolar North Atlantic Program

Rapid Climate Change (RAPID) is a £20 million, six-year (2001-2007) programme of the Natural Environment Research Council. The programme aims to improve our ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.

[oren]

Nice suggestions, will do.