2018 sea ice area and extent data

[gerontocrat]

JAXA ARCTIC EXTENT 11,871,945 km2（December 28, 2018）

- Extent gain 26k, 32k below average (last 10 years) for the day,
- Extent is 2nd lowest in the satellite record,
- Freezing to date from minimum is 382 k (4.9%) below the 10 year average extent gain,
- On average (last 10 years) 78.3 % of the increase in extent from min to max is done.

An extra line in the table attached based on average extent increase in the last 5 years has been added. This is because extent gain in 2012-13 was so large (rebound from record low minimum) that it distorts the average. The outcome from using the 10 year average extent gain from now is a maximum of 13.95 million km2 (70k > 2017).  Using the previous 5 years's average extent gain, the resulting maximum is 13.79 million km2, (90k < 2017).

Extent gain from minimum on this day greatly below average. On average (last 10 years) three quarters of extent gain from min to max is now done with on average 73 days to maximum.

GFS indicates that overall the Arctic temperature anomaly will be between +1.5 and +4 for the next week or so.
______________________________________________________________________
ps: *The 2010's average figure I use in the attached table excludes 2018. I exclude 2018 (from all JAXA and NSIDC tables and graphs) so that the difference of the current year with the 2010's decade to date average is not modified by the current year data.
______________________________________________________________________

[uniquorn]

<snippage>Greenland Sea - export down the Fram?

amsr2-uhh and jaxa, Greenland Sea, nov9-dec27

[gerontocrat]

NSIDC Total Area as at 28 December (5 day trailing average) =10,890,620 km2

Total Area           10,890,620    km2       -55,867    km2   <    2010's average.  186,802    k   >   2017 -552,570    k   <    2000's average.           Total Gain    6    k    Peripheral Seas    3    k   gain Central Seas__   -16    k   loss Other Seas___    19    k   gain           Peripheral Seas          Bering _______    6    k   gain Baffin  Bay____   -11    k   loss Greenland____    3    k   gain Barents ______    6    k   gain           CAB Seas          Beaufort_____   -9    k   loss CAA_________   -1    k   loss East Siberian__   -1    k   loss Central Arctic_    7    k   gain           Kara_________   -10    k   loss Laptev_______   -2    k   loss Chukchi______    0    k   gain           Other Seas          Okhotsk______    3    k   gain St Lawrence___    1    k   gain Hudson Bay___    15    k   gain

Area gain of 6 k is below average by 40k on this day.
Area is:
- 187k greater than 2017,
- 56k less than the 2010's average,
- 553k less than the 2000's average.

Area gain switched from well above average to extremely low in the last 4 days, mostly due to area losses in the Baffin, Kara and Laptev seas.

Other stuff
GFS indicates that overall the Arctic temperature anomaly will be between +1.5 and +4 for the next week or so.

Regional variations suggest that while the main Arctic freezes solid and the Bering quickly increases in ice area and extent, the Atlantic Front may still resist icing up.

[Stephan]

If one would exclude Hudson from the table the arctic sea ice area would have decreased since Dec 25!

[gerontocrat]

JAXA ARCTIC EXTENT 11,964,034 km2（December 29, 2018）

- Extent gain 92k, 24k above average (last 10 years) for the day,
- Extent is 2nd lowest in the satellite record,
- Freezing to date from minimum is 358 k (4.6%) below the 10 year average extent gain,
- On average (last 10 years) 78.9 % of the increase in extent from min to max is done.

An extra line in the table attached based on average extent increase in the last 5 years has been added. This is because extent gain in 2012-13 was so large (rebound from record low minimum) that it distorts the average. The outcome from using the 10 year average extent gain from now is a maximum of 13.97 million km2 (90k > 2017).  Using the previous 5 years's average extent gain, the resulting maximum is 13.83 million km2, (50k < 2017).


GFS indicates that overall the Arctic temperature anomaly will be between +2.5 and +4 for the next week or so.
______________________________________________________________________
ps: *The 2010's average figure I use in the attached table excludes 2018. I exclude 2018 (from all JAXA and NSIDC tables and graphs) so that the difference of the current year with the 2010's decade to date average is not modified by the current year data.
______________________________________________________________________
[/quote]

[gerontocrat]

NSIDC Total Area as at 29 December (5 day trailing average) = 10,927,399 km2

Total Area           10,927,399    km2       -78,509    km2   <    2010's average.  177,915    k   >   2017 -554,244    k   <    2000's average.           Total Gain    37    k    Peripheral Seas    15    k   gain Central Seas__    2    k   gain Other Seas___    20    k   gain           Peripheral Seas          Bering _______    9    k   gain Baffin  Bay____   -1    k   loss Greenland____   -1    k   loss Barents ______    9    k   gain           CAB Seas          Beaufort_____   -5    k   loss CAA_________   -2    k   loss East Siberian__   -3    k   loss Central Arctic_    10    k   gain           Kara_________    1    k   gain Laptev_______   -2    k   loss Chukchi______    2    k   gain           Other Seas          Okhotsk______    2    k   gain St Lawrence___    2    k   gain Hudson Bay___    16    k   gain

Area gain of 37 k is below average by 23k on this day.
Area is:
- 178k greater than 2017,
- 79k less than the 2010's average,
- 554k less than the 2000's average.

Area gain switched from well above average to low in the last 5 days, mostly due to area losses in the Baffin, Kara and Laptev seas, which are now about over..

Other stuff
GFS indicates that overall the Arctic temperature anomaly will be between +2.5 and +4 for the next week or so.

Regional variations suggest that while the main Arctic freezes solid and the Bering quickly increases in ice area and extent, the Atlantic Front may still resist icing up.

[Juan C. García]

[ADS NIPR VISHOP (JAXA)] ASI Extent.

December 30^th, 2018:
     12,053,135 km², an increase of 89,101 km².


P.S.
Hello everybody.
Sorry that I have not being here for several days.
I made a trip to Oaxaca (México) and I was supposed to have a good internet connection. Finally it didn't happen and what it is worst, it end up my subscription with Office 365.
I will try to do the work with Google spreadsheets.

Wish me luck...

[Juan C. García]

[ADS NIPR VISHOP (JAXA)] ASI Extent.

December 30^th, 2018:
     12,053,135 km², an increase of 89,101 km².
     2018 is the 2^nd lowest on record.


P.S. I will be on holiday tomorrow and I will post on January 1st, 2019.
¡Happy new year!

[Tor Bejnar]

P.S. I will be on holiday tomorrow and I will post on January 1st, 2019.
¡Happy new year!

By my calculations, 2019 starts in just under 5 hours.  Until then, Happy Old Year!

Oh yes, Arctic sea ice ... I predict we'll end the year in 2nd place.  (Unlike my vote in another thread)

[gerontocrat]

JAXA ARCTIC EXTENT 12,053,135 km2（December 30, 2018）

- Extent gain 89k, 43k above average (last 10 years) for the day,
- Extent is 2nd lowest in the satellite record,
- Freezing to date from minimum is 315 k (4.0%) below the 10 year average extent gain,
- On average (last 10 years) 79.4 % of the increase in extent from min to max is done.

An extra line in the table attached based on average extent increase in the last 5 years has been added. This is because extent gain in 2012-13 was so large (rebound from record low minimum) that it distorts the average. The outcome from using the 10 year average extent gain from now is a maximum of 14.02 million km2 (180k > 2017).  Using the previous 5 years's average extent gain, the resulting maximum is 13.83 million km2, (0k = 2017).


GFS indicates that overall the Arctic temperature anomaly will be between +3.5 and +4 for the next 3 days and reduce to zero by a few days after that. However, cold and warm pulses continue travelling up the Atlantic Front to north of Novaya Zemla.
______________________________________________________________________
ps: *The 2010's average figure I use in the attached table excludes 2018. I exclude 2018 (from all JAXA and NSIDC tables and graphs) so that the difference of the current year with the 2010's decade to date average is not modified by the current year data.
______________________________________________________________________

[Stephan]

Dear Juan,

I wish you a Happy and Healthy and Successful and Peaceful New Year.
Thanks for updating us almost everyday about the Sea Ice Extent.

Greetings from Germany
Stephan

[ADS NIPR VISHOP (JAXA)] ASI Extent.

December 30^th, 2018:
     12,053,135 km², an increase of 89,101 km².
     2018 is the 2^nd lowest on record.


P.S. I will be on holiday tomorrow and I will post on January 1st, 2019.
¡Happy new year!

[Altai]

Happy new year to everyone and greetings from Russia.!

[gerontocrat]

NSIDC Total Area as at 30 December (5 day trailing average) = 10,969,557 km2

Total Area           10,969,557    km2       -94,823    km2   <    2010's average.  168,884    k   >   2017 -549,994    k   <    2000's average.           Total Gain    42    k    Peripheral Seas    24    k   gain Central Seas__    0    k   gain Other Seas___    18    k   gain           Peripheral Seas          Bering _______    10    k   gain Baffin  Bay____    6    k   gain Greenland____    3    k   gain Barents ______    5    k   gain           CAB Seas          Beaufort_____   -2    k   loss CAA_________   -2    k   loss East Siberian__   -5    k   loss Central Arctic_    7    k   gain           Kara_________   -1    k   loss Laptev_______   -3    k   loss Chukchi______    4    k   gain           Other Seas          Okhotsk______    5    k   gain St Lawrence___    0    k   gain Hudson Bay___    12    k   gain

Area gain of 42 k is below average by 16k on this day.
Area is:
- 169k greater than 2017,
- 95k less than the 2010's average,
- 550k less than the 2000's average.

Area gain switched from well above average to low in the last 6 days, mostly due to area losses in the Baffin, Kara and Laptev seas, which are now about over..

Other stuff
GFS indicates that overall the Arctic temperature anomaly will be between +3.5 and +4 for the next 3 days and reduce to zero by a few days after that. However, cold and warm pulses continue travelling up the Atlantic Front to north of Novaya Zemla.

Regional variations suggest that while the main Arctic freezes solid and the Bering quickly increases in ice area and extent, the Atlantic Front may still resist icing up.
[/quote]

[Shared Humanity]

Happy New Year from a truth refugee in Hair Furor's America.

[Alison]

Happy New Year!

[gerontocrat]

JAXA ARCTIC EXTENT 12,164,925 km2（December 31, 2018）

- Extent gain 112k, 89k above average (last 10 years) for the day, the 3rd day of very high gains.
- Extent is 3rd lowest in the satellite record,
- Freezing to date from minimum is 227 k (2.9%) below the 10 year average extent gain,
- On average (last 10 years) 79.6 % of the increase in extent from min to max is done.

An extra line in the table attached based on average extent increase in the last 5 years has been added. This is because extent gain in 2012-13 was so large (rebound from record low minimum) that it distorts the average. The outcome from using the 10 year average extent gain from now is a maximum of 14.11 million km2 (230k > 2017).  Using the previous 5 years's average extent gain, the resulting maximum is 13.97 million km2, (90k > 2017).


GFS indicates that overall the Arctic temperature anomaly will be between +3.5 and +4 for the next 3 days and reduce to zero by a few days after that. However, cold and warm pulses continue travelling up the Atlantic Front to north of Novaya Zemla.
______________________________________________________________________
ps: *The 2010's average figure I use in the attached table excludes 2018. I exclude 2018 (from all JAXA and NSIDC tables and graphs) so that the difference of the current year with the 2010's decade to date average is not modified by the current year data.
______________________________________________________________________

[gerontocrat]

NSIDC Total Area as at 31 December (5 day trailing average) = 11,023,811 km2

Total Area           11,023,811    km2       -98,488    km2   <    2010's average.  181,349    k   >   2017 -541,648    k   <    2000's average.           Total Gain    54    k    Peripheral Seas    29    k   gain Central Seas__    5    k   gain Other Seas___    20    k   gain           Peripheral Seas          Bering _______    7    k   gain Baffin  Bay____    11    k   gain Greenland____    5    k   gain Barents ______    6    k   gain           CAB Seas          Beaufort_____    1    k   gain CAA_________   -2    k   loss East Siberian__   -3    k   loss Central Arctic_    9    k   gain           Kara_________   -1    k   loss Laptev_______   -3    k   loss Chukchi______    5    k   gain           Other Seas          Okhotsk______    8    k   gain St Lawrence___    0    k   gain Hudson Bay___    11    k   gain

Area gain of 54 k is below average by 4k on this day.
Area is:
- 181k greater than 2017,
- 98k less than the 2010's average,
- 541k less than the 2000's average.

Area gain switched from well above average to low in the last 6 days, mostly due to area losses in the Baffin, Kara and Laptev seas, which are now about over..

Other stuff
GFS indicates that overall the Arctic temperature anomaly will be between +3.5 and +4 for the next 3 days and reduce to zero or below by a few days after that. However, cold and warm pulses continue travelling up the Atlantic Front to north of Novaya Zemla.

Regional variations suggest that while the main Arctic freezes solid and the Bering quickly increases in ice area and extent, the Atlantic Front may still resist icing up part of the time.

[Juan C. García]

Seems that ADS-NIPR-VISHOP will need time to start the 2019 data.
Here are the values for the end of the year.

[ADS NIPR VISHOP (JAXA)] ASI Extent.

December 31^st, 2018:
     12,164,925 km², an increase of 111,790 km².
     2018 is the 3^rd lowest on record.

[gerontocrat]

2018 has been 'n gone.
What happened?

An occasional series of graphs commences.

Attached are the total arctic area and extent graphs for 2018. They do show the low max last March and the slow freeze in late sept /oct. They also conceal the great variation in individual Arctic Seas.

[Phil42]

Back from holidays as well. Happy new year everyone from Switzerland.

I'll do some posts about things I observed this past month / year. Since this is my first year of following the cryosphere this closely and most people in this forum know a lot more than me, I'll try to focus on data and do as little interpretation as possible.

To start off, ASI Extent has passed the 12M km² mark on 30^th December. This is the second latest date of this happening with the latest being 2017 (2018) on 2^nd January.

The timeframe around the minimum of 2018 (15.3.2018 - 15.3.2019) had 234 days of Arctic Sea Ice Extent below 12'000'000 km2, which is:

 - 2^nd highest on record
 - 8 days more than the 2010's (2010-2018) average
 - 4 days more than 2017
 - 3 days less than the record year 2016

A lot of statistics covering Arctic sea ice extent show a slowing (some say even a halting) of decline since 2012. The "days below 12M km² extent" shows the exact opposite. Maybe a sign of continued winter ice loss or maybe just a 4-year-long fluctuation, we will know more in the future. But at the moment it seems like the days of high extent numbers are getting fewer and fewer each year.

[Phil42]

December 2018 had an average Arctic Sea Ice Extent of 11'378'371 km². This is:

 - 4^th lowest on record
 - 85'479 km² less than the 2010's (2010-2018) average
 - 96'038 km² more than 2017
 - 377'435 km² more than the record year 2016

The second image shows the ranks of average extent per month in the last 15 years. Read it as "March 2018 had the second lowest average Arctic sea ice extent in recorded history".

As you can see, there is a clear trend here of average extent declining, moreso in winter than in summer months in recent years.

[Phil42]

Now onto some statistics regarding the day rankings in 2018. I'm really not sure if those have any significance, but I think they are interesting to look at nontheless.

The first "table" shows the average rank a day holds in that year. Read it as "A day in 2015 is ranked as 6.2 lowest in average".

2018 stands at 4.1, which is higher than the two previous years, but lower than all other years. So 2018 fits the trend of overall decline really well.


The second "table" shows the average rank a day held that year at the end of that year. Read it as "At the end of 2015, a day in 2015 was ranked as 3.8 lowest in average".

My interpretation of this statistics is that it should show whether the speed of ice decline is slowing or accelerating. 2018 is slightly above average, but this is mainly caused by the very high extent numbers in July, so I don't know it that tells us anything about the overall trend.

[Phil42]

Now a straight-forward statistics showing how many records were broken or nearly broken in 2018.

This year had:
- 68 days of lowest Arctic sea ice extent.
- 203 days where Arctic sea ice extent was ranked in lowest 3.
- 269 days where Arctic sea ice extent was ranked in lowest 5.

Out of the 68 records:
- 25 were in Juanuary
- 25 in February
- 7 in March
- 9 in April
- 2 in October

[Phil42]

To conclude I'd like to take a look at the 365-day trailing average of Arctic sea ice extent.

The average extent of 2018 was 9'919'855 km², this is:
- 2^nd lowest on record
- 203'876 km² higher than the record year 2016
- 35'785 km² lower than the 3^rd-placed-year 2017
*- All years except 2012/2016/2017/2018 stand above 10'000'000 km².


The first graph shows the 365-day trailing average in the last 5 years. While there is some fluctuation in the past 2-3 years, the linear trend shows a clear decline. The lowest 365-day-average of Arctic sea ice extent was 30^th March 2017 with 9'683'735 km².

The second graph shows the development of the 365-day-average in 2018. I think the timeframe is too small for it to have any significance, but the trend slightly downward as well.

[oren]

An excellent chain of posts Phil. Wonderful stats. Thank you.
I would expect the 365-day average to rise in the next two months, as 2018 was lowest on record in Jan and Feb, and for now it seems 2019 may be higher.

[HapHazard]

Great posts, Phil - thanks for that.

Also, congrats on the Swiss team in the World Juniors so far! 

[gerontocrat]

A look at groups of seas.
First - The "pacific gateway" - the Bering and Chukchi Seas in 2018

The Bering Sea melted early and froze late. But then the December freeze was well above average. At the end of the year both extent and area were close to the March 2018 maximum. This is a reversal of recent year trends. Many of us were thinking that maybe the Bering had become a basically maritime climate sea that occasionally had some ice in it.

Apart from the late Feb to early March dip (the SSW event?)The Chukchi melt was pretty much average until late September. Then the melt season extended  to the second week in October followed by a rapid freeze.

The next post will look at long-term trends in these seas

[gerontocrat]

The "pacific gateway" - the Bering and Chukchi Seas in 2018 - trends since 1979

The measure I used for this is the number of days sea ice area is less than n% of the 1980's sea ice extent maximum, where n is <5% (= 95% or more ice-free), <15% (which for an NSIDC pixel = zero), and <50% (more than 50% means more ice than not).

The three graphs attached show that in both seas there is a clear upward trend, but less pronounced for the <50% measure. Of note is that the Chukchi was never 95% ice-free until 2007.

[gerontocrat]

The "pacific gateway" - the Bering and Chukchi Seas in 2018 - Climate Change - towards maritime seas vs icy deserts.

As each sea loses ice the climate must trend to maritime (milder, wetter)  from an icy desert (cold, dry). The measure I used for this is to plot the change in the percentage of open water compared with the total sea area.  I did this for the maximum ice month, the minimum ice month, the three minimum ice months, and for the entire calendar year.

The graphs attached show that in both seas there is a clear upward trend. The Bering Sea is a maritime sea for most of the year. In recent years it has been losing its winter ice. The Chukchi is still more an ice desert than not. But in summer the percentage of open water is consistently increasing, while the maximum ice month of March shows little change.

[Klondike Kat]

Phil,
Yes, the linear trend shows a decline.  But is it the best fit?

[oren]

The "pacific gateway" - the Bering and Chukchi Seas in 2018 - trends since 1979

The measure I used for this is the number of days sea ice area is less than n% of the 1980's sea ice extent maximum, where n is <5% (= 95% or more ice-free), <15% (which for an NSIDC pixel = zero), and <50% (more than 50% means more ice than not).

The three graphs attached show that in both seas there is a clear upward trend, but less pronounced for the <50% measure. Of note is that the Chukchi was never 95% ice-free until 2007.

A great set of posts. Thanks Gerontocrat.
May I suggest another of these charts, a n<90%, which will capture the phenomena of early melt onset and late final freeze in the Chukchi. I think there are many more days where the Chukchi is not at full ice capacity, compared to previous decades.

[gerontocrat]

Now my technology is operational gain (fingers crossed) another look at groups of seas.

Second Group - Canadian Seas - Hudson bay, Baffin Bay, the Canadian Archipelago.

All these seas showed a recovery in sea ice extent and area. I attach the extent graphs for 2018.
The next posts will look at long-term trends in these seas.

[gerontocrat]

Second Group - Canadian Seas - Hudson Bay, Baffin Bay, the Canadian Archipelago.
Longer-term trends

Ice-Free days. The measure I used for this is the number of days sea ice area is less than n% of the 1980's sea ice extent maximum, where n is <5% (= 95% or more ice-free), <15% (which for an NSIDC pixel = zero), and <50% (more than 50% means more ice than not).

The three graphs attached show that for Baffin Bay and the Canadian Archipelago there is a clear but modest upward trend. The upward trend for Hudson bay may not be statistically significant.

The Canadian Archipelago is very much an icy desert for the whole year, while the Baffin in some years is more than 50% ice-free for more than half the year.

[gerontocrat]

Second Group - Canadian Seas - Hudson Bay, Baffin Bay, the Canadian Archipelago.
Longer-term trends

Open Water percentage Climate Change - towards maritime seas vs icy deserts.

As each sea loses ice the climate must trend to maritime (milder, wetter)  from an icy desert (cold, dry). The last measure I used for this is to plot the change in the percentage of open water compared with the total area of each sea.  I did this for the maximum ice month, the minimum ice month, the three minimum ice months, and for the entire calendar year.

The Canadian Archipelago has on average only 20 to 30% open water - i.e. predominantly and ice desert.
Baffin Bay has on average only 70% open water - i.e. more ice free than not which must increase the maritime climate influence for a good part of the year.
Hudson Bay is more or less an icy desert for half the year and an open sea for half the year.

The graphs attached also show that there is no clear upward trend. AGW seems to have passed them by, which is a bit of a contrast with elsewhere in the Arctic.

[Stephan]

Second Group - Canadian Seas - Hudson Bay, Baffin Bay, the Canadian Archipelago.
Longer-term trends

[...]

The graphs attached also show that there is no clear upward trend. AGW seems to have passed them by, which is a bit of a contrast with elsewhere in the Arctic.

Is this probably a cause of the general wind and drift direction that a lot of sea ice is pushed from the CAB towards the Canadian Archipelago and then pressed through the channels southwards, so that a possible melting effect due to climate change is made up by new and more fragmented ice that is coming down from the CAB?

[Phil.]

I think this makes sense, the flow through some of the northern channels is much more mobile in the summers now.  The very thick ice to the north of the archipelago is much depleted now.

[gerontocrat]

GROUP 3 - "Atlantic Front" - The Greenland, Barents, Kara & Laptev Seas (4.2 million km2)

Extent graphs 2018

The Greenland Sea showed the continued strong decline in ice content. This may be partly due to reduced flow of sea ice down the Fram Strait in recent years.

The Barents Sea was a bit late is commencing the melt but the Autumn refreeze was late and slow.

The Kara Sea was late is commencing the melt and then melted out extremely fast. The nearly ice-free period was extended, the Autumn refreeze was late and extremely fast.

The Laptev Sea melted out early and extremely fast, the virtually ice-free period was much longer than usual, and the Autumn refreeze was late and extremely fast.

The next posts will look at long-term trends in these seas.

[gerontocrat]

GROUP 3 - "Atlantic Front" - The Greenland, Barents, Kara & Laptev Seas (4.2 million km2)
Longer-term trends

Ice-Free days. The measure I use for this is the number of days sea ice area is less than n% of the 1980's sea ice extent maximum, where n is <5% (= 95% or more ice-free), <15% (which for an NSIDC pixel = zero), and <50% (more than 50% means more ice than not).

The three graphs attached show that all seas are showing an upward trend in days when ice area is less than each percentage (5, 15 and 50 %).
It is the Barents Sea that is showing the greatest change and is now more than 50% ice-free for most of the year.
Without sea ice flowing down the Fram Strait, it is possible that the Greenland Sea would also show much more ice loss.

[gerontocrat]

GROUP 3 - "Atlantic Front" - The Greenland, Barents, Kara & Laptev Seas (4.2 million km2)

Open Water percentage Climate Change - towards maritime seas vs icy deserts since 1979.

As each sea loses ice the climate must trend to maritime (milder, wetter)  from an icy desert (cold, dry). The measure I use for this is to plot the change in the percentage of open water compared with the total area of each sea.  I have done this for the maximum ice month, the minimum ice month, the three minimum ice months, and for the entire calendar year.

The Barents Sea is now nearly ice-free for at least 3 months of the year. Of more significance is that open water has increased from around 30% to 60% in the maximum ice area month of March.
The Greenland Sea open water percentage  has increased from around 80% to 90% in the 3 minimum ice months, and in the maximum ice month of March open water has increased to  60% from 40%.
It is a summer story for both the Kara and Laptev Seas. While in winter the seas are frozen over, in the three minimum ice months in the Kara Sea open water has increased from around 60-70% to over 90% and in the Laptev Sea from around 50% to over 80%.

This process of "Atlantification" has significantly moved these seas towards becoming climatically part of the Atlantic Ocean as opposed to the icy desert of the Central Arctic.

[gerontocrat]

GROUP 4 - The 3 Central Arctic Seas - Beaufort, East Siberian and Central Arctic Seas (5.5 million km2)

Extent graphs 2018

The Beaufort Sea melted late, minimum well above 2010's average, and refroze early

The East Siberian Sea melted late, minimum well below 2010's average, and refroze late.

The Central Arctic Sea melt was early, minimum well below 2010's average, and refroze late.


The next posts will look at longer-term trends in these seas.

[echoughton]

Well Done, Geron!!
Very informative and thorough. I am going ask Neven to double your salary!! 

[gerontocrat]

GROUP 4 - The 3 Central Arctic Seas - Beaufort, East Siberian and Central Arctic Seas (5.5 million km2)
Longer-term trends

Ice-Free days. The measure I use for this is the number of days sea ice area is less than n% of the 1980's sea ice extent maximum, where n is <5% (= 95% or more ice-free), <15% (which for an NSIDC pixel = zero), and <50% (more than 50% means more ice than not).

The graphs for the Beaufort and East Siberian Seas attached show an upward trend in days when ice area is less than each percentage (5, 15 and 50 %). The 5% and 15% graphs show clearly how the reduction in sea ice really became apparent from 2007 onwards . At no time is the Central Arctic ice area less than 50% of total sea area. When n=80% is used, the same change in 2007 is observed.

Perhaps the 2007 extraordinary summer melt did make or highlight a permanent change in these seas at least.

[gerontocrat]

GROUP 4 - The 3 Central Arctic Seas - Beaufort, East Siberian and Central Arctic Seas (5.5 million km2) Longer-term trends

Open Water percentage Climate Change - towards maritime seas vs icy deserts since 1979.

As each sea loses ice the climate must trend to maritime (milder, wetter)  from an icy desert (cold, dry). The measure I use for this is to plot the change in the percentage of open water compared with the total area of each sea.  I have done this for the maximum ice month, the minimum ice month, the three minimum ice months, and for the entire calendar year.
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It is essentially a summer story for these seas. Solidly frozen in winter, in summer the percentage of open water for the three minimum months of August, September and October is increasing:-
- in the Beaufort Sea from 30% to approaching 70%,
- in the East Siberian from 30% to well over 70%,
- in the Central Arctic Sea from 10% to over 25%,
- for the average of these three seas from 20% to over 40%.

These seas are in essence still icy deserts.

Overall

[gerontocrat]

GROUP 5 - "Non-Arctic Seas" - St Lawrence & Okhotsk (1.9 million Km2)

Extent graphs 2018

The maximum in both seas was well above the 2010s and 200s average. The melt to zero ice, the length of time at zero ice, and the December start of refreeze were all at around average

The next posts will look at longer-term trends in these seas.

[gerontocrat]

GROUP 5 - "Non-Arctic Seas" - St Lawrence & Okhotsk (1.9 million Km2)
Longer-term trends

Ice-Free days. The measure I use for this is the number of days sea ice area is less than n% of the 1980's sea ice extent maximum, where n is <5% (= 95% or more ice-free), <15% (which for an NSIDC pixel = zero), and <50% (more than 50% means more ice than not).

The number of ice-free days on all the measures for the Okhotsk and for the 15% and 50% measures for the St Lawrence varies muchly from year to year. inserting a trend line makes it clear that there is an upward trend in ice-free days.

In contrast, the 5% (95 % ice free) measure for the St Lawrence is very stable from year to year. The reason for this difference from the 15% and 50% measure is a total mystery to me.

[gerontocrat]

GROUP 5 - "Non-Arctic Seas" - St Lawrence & Okhotsk (1.9 million Km2)
Longer-term trends

Open Water percentage Climate Change - towards maritime seas vs icy deserts since 1979.

As each sea loses ice the climate must trend to maritime (milder, wetter)  from an icy desert (cold, dry). The measure I use for this is to plot the change in the percentage of open water compared with the total area of each sea.  I have done this for the maximum ice month, the minimum ice month, the three minimum ice months, and for the entire calendar year.
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Volatility from year to year is high, adding trend lines has helped.

It is essentially a winter story for these seas. Always ice-free in summer, the percentage of open water for the three maximum months of February March and April is increasing:-
- in the Okhotsk Sea from just under 40% to approaching 70%,
- in the St Lawrence Sea from around 70% to around 80%,
- for the average of these two seas from just over 40% to just under 70%.

These seas are in essence now around 90% ice-free on a yearly average .

[gerontocrat]

And here are the graphs for the total of the 14 Arctic Seas as provided by NSIDC.

Analysis - gradual movement towards ice-free.

[Stephan]

It is time to compare December 2018 Arctic Sea Ice Extent in the context of the long term trend.
The average December (1979-2018) had 12,71 M km². December 2018 was less (11,86 M km²). If you add the long-term linear trend (see red line in the graph) December 2018 "should have had" 11,53 M km². This makes December 2018 lie above the trend line (like November 2018, but unlike October 2018).
See attached graph.