As anticipated in a previous post, Arctic ice extent appears to have peaked under the 15M km2 threshold.  An earlier discussion noted that the wavy Polar Vortex that froze Texas with cold Arctic air in February, allowed warmer southern air into Arctic regions, reducing ice extent.  The ice recovered afterward ( see March 1, 2021 Arctic Ice Recovers from PV Hit ), but 2021 was no longer going to reach 15M km2.  As shown by the graph below, ice extents this year did persist and draw close to the 14 year average, before beginning the melt season this week.

Starting March MASIE 2021 shows Arctic extents were about 400k km2 below average, but for the first 20 days added 200k while the average lost about 100k, reducing the difference to 85k km2 on day 80.  Now in the last 3 days the melt season has erased the gains in 2021 and restored the deficit to nearly 300k km2, 2% of the 14-year average.  SII reported mostly lower extents than MASIE, but presently the two are similar.  The table shows the distribution of ice over the Arctic regions.

Interestingly, both Okhotsk and Barents Seas peaked well above average, and are still in surplus after starting to retreat.  The main deficits are in Bering and Baffin Bay.  The central Arctic, Siberian and Canadian regions remain solidly frozen.

Background previous post Arctic Ice Moment of Truth 2021

For ice extent in the Arctic, the bar is set at 15M km2. The average peak in the last 14 years occurs on day 62 at 15.04M km2 before descending, though the average can still be above 15M at late as day 73.  Nine of the last 14 years were able to clear 15M, but recently only 2016 and 2020 ice extents cleared the bar at 15M km2; the others came up short. The actual annual peak ice extent day varied between day 59 (2016) to day 82 (2012).

The animation shows in two weeks how this year’s ice extents contracted and then regrew greater than before, coincidental with the wavy Polar Vortex (PV) first admitting warmer southern air and then keeping the cold air in.

As reported previously, most of the action was firstly in the Pacific, especially Sea of Okhotsk upper left, ice shrinking one week by 200k km2 and rapidly growing back 210k km2 ice extent the next.  Okhotsk ice is now 1.1M km2, 96% of 2020 max.  On the Atlantic side, Barents sea upper right lost 100k km2 retreating from Svalbard, then gained 120k km2 back.  Greenland Sea ice middle right lost 100k km2, and then gained 150k km2.  Barents now has 3% more ice than 2020 max, while Greenland sea ice is 85% of last year’s max.

Drift ice in Okhotsk Sea at sunrise.

For more on the Pacific basins see post Meet Bering and Okhotsk Seas

As anticipated in the previous post reprinted below, Arctic ice extent appears to have peaked under the 15M km2 threshold.  An earlier discussion at 2020 year end noted that March actually ends up with less ice extent than end of February, so the rest of the month is not likely to add any more ice.  Here is the graph for March including yesterday.

The graph shows this year did recover from a 400k km2 deficit to the 14-year average, to about 100k by day 70, and has now fallen back to almost 300k km2 down (2%).  It is also apparent that extent will likely decline in the next two weeks, by about 300k km2 on average, already matched by 2021.  Climatology uses SII March monthly average as the annual maximum, so that will come out lower as well.

Interestingly, both Okhotsk and Barents Seas peaked well above 2020, and are now starting to retreat, along with other marginal basins.  The central Arctic, Siberian and Canadian regions remain solidly frozen.

Background previous post Arctic Ice Moment of Truth 2021

For ice extent in the Arctic, the bar is set at 15M km2. The average peak in the last 14 years occurs on day 62 at 15.04M km2 before descending, though the average can still be above 15M at late as day 73.  Nine of the last 14 years were able to clear 15M, but recently only 2016 and 2020 ice extents cleared the bar at 15M km2; the others came up short. The actual annual peak ice extent day varied between day 59 (2016) to day 82 (2012).

The animation shows in two weeks how this year’s ice extents contracted and then regrew greater than before, coincidental with the wavy Polar Vortex (PV) first admitting warmer southern air and then keeping the cold air in.

As reported previously, most of the action was firstly in the Pacific, especially Sea of Okhotsk upper left, ice shrinking one week by 200k km2 and rapidly growing back 210k km2 ice extent the next.  Okhotsk ice is now 1.1M km2, 96% of 2020 max.  On the Atlantic side, Barents sea upper right lost 100k km2 retreating from Svalbard, then gained 120k km2 back.  Greenland Sea ice middle right lost 100k km2, and then gained 150k km2.  Barents now has 3% more ice than 2020 max, while Greenland sea ice is 85% of last year’s max.

All of this means that 2021 will be hard pressed to pass the 15M km2 threshold.  The graph below shows the situation evolving over the last two weeks anticipating the annual maximum to appear within the fortnight.

Note that Sea Ice Index (SII) went offline day 51 so the MASIE record alone shows the loss of ice extent ending day 56 and climbing up to the present.  The NH ice extent gap is at 244k km2, or 1.6%.  Since the 14 year average has already peaked, further growth will narrow the margin.  (Note that ice extent is affected also by winds piling up drift ice, as well as melting from intrusions of warmer air or water.)

Last year surpassed the average while other recent years were lower.  We shall see what this year does with only 10 days or so to make a difference.

The main deficit to average is in Baffin Bay, partly offset by a surplus in Barents.  Smaller pluses and minuses are found in other regions.

Typically, Arctic ice extent loses 67 to 70% of the March maximum by mid September, before recovering the ice in building toward the next March.

What will the ice do this year?  Where will 2020 rank in the annual Arctic Ice High Jump competition?

Drift ice in Okhotsk Sea at sunrise.

For more on the Pacific basins see post Meet Bering and Okhotsk Seas

For ice extent in the Arctic, the bar is set at 15M km2. The average peak in the last 14 years occurs on day 62 at 15.04M km2 before descending, though the average can still be above 15M at late as day 73.  Nine of the last 14 years were able to clear 15M, but recently only 2016 and 2020 ice extents cleared the bar at 15M km2; the others came up short. The actual annual peak ice extent day varied between day 59 (2016) to day 82 (2012).

The animation shows in two weeks how this year’s ice extents contracted and then regrew greater than before, coincidental with the wavy Polar Vortex (PV) first admitting warmer southern air and then keeping the cold air in.

As reported previously, most of the action was firstly in the Pacific, especially Sea of Okhotsk upper left, ice shrinking one week by 200k km2 and rapidly growing back 210k km2 ice extent the next.  Okhotsk ice is now 1.1M km2, 96% of 2020 max.  On the Atlantic side, Barents sea upper right lost 100k km2 retreating from Svalbard, then gained 120k km2 back.  Greenland Sea ice middle right lost 100k km2, and then gained 150k km2.  Barents now has 3% more ice than 2020 max, while Greenland sea ice is 85% of last year’s max.

All of this means that 2021 will be hard pressed to pass the 15M km2 threshold.  The graph below shows the situation evolving over the last two weeks anticipating the annual maximum to appear within the fortnight.

Note that Sea Ice Index (SII) went offline day 51 so the MASIE record alone shows the loss of ice extent ending day 56 and climbing up to the present.  The NH ice extent gap is at 244k km2, or 1.6%.  Since the 14 year average has already peaked, further growth will narrow the margin.  (Note that ice extent is affected also by winds piling up drift ice, as well as melting from intrusions of warmer air or water.)

Last year surpassed the average while other recent years were lower.  We shall see what this year does with only 10 days or so to make a difference.

The main deficit to average is in Baffin Bay, partly offset by a surplus in Barents.  Smaller pluses and minuses are found in other regions.

Typically, Arctic ice extent loses 67 to 70% of the March maximum by mid September, before recovering the ice in building toward the next March.

What will the ice do this year?  Where will 2020 rank in the annual Arctic Ice High Jump competition?

Drift ice in Okhotsk Sea at sunrise.

For more on the Pacific basins see post Meet Bering and Okhotsk Seas

At this point in the Arctic refreezing phase, LIFO inventory accounting comes into play.  Last-In, First-out is one accepted way to price the value of a company’s inventory.  For Arctic ice, it means that basins that are last to freeze over in winter are the first to melt out in the summer.  For example, in Mid January 2021, total NH ice extent is 91% of last March maximum, so most basins have long been covered with ice.  The last 9% will be added in four places (present % of max is noted):

Bering Sea        62%
Okhotsk Sea     70%
Barents Sea      58%
Baffin Bay         66%

In the Pacific animation above, Bering on the right adds ice extent from 261k km2 to 513k km2 since Jan. 1, while Okhotsk goes from 500k km2 to 800k km2.  Together they will likely add ~650k km2 more by March maximum.  

On the Atlantic side, Barents Sea added only ~100k km2 so far in January.  More interesting on the right side is the Baltic Sea quadrupled from 9K km2 to 42k km2.  While the Baltic extent is not large by comparison, it is already 38% greater than last March maximum, so that is surprising.

Normally, ice in the Yellow Sea is insignificant, but this year is different.  Perhaps you saw reports like this one from gcaptain Sea Ice Slows Ships In North China Ports  Excerpts in italics with my bolds.

By Muyu Xu and Chen Aizhu (Reuters) – Chinese ports and marine safety authorities are on high alert as an expansion of sea ice makes it tougher for ships to berth and discharge at key energy product import terminals along the coast of northern Bohai Bay.

A cold wave sweeping the northern hemisphere has plunged temperatures across China to their lowest in decades, boosting demand for power and fuel to historic highs in the world’s largest energy consumer.

Bohai Bay appears in the upper right corner, with Beijing nearby. Yellow Sea extent doubled in January up to 28,000 km2, which is twice the maximum last March.

Background on Okhotsk Sea

NASA describes Okhotsk as a Sea and Ice Factory. Excerpts in italics with my bolds.

The Sea of Okhotsk is what oceanographers call a marginal sea: a region of a larger ocean basin that is partly enclosed by islands and peninsulas hugging a continental coast. With the Kamchatka Peninsula, the Kuril Islands, and Sakhalin Island partly sheltering the sea from the Pacific Ocean, and with prevailing, frigid northwesterly winds blowing out from Siberia, the sea is a winter ice factory and a year-round cloud factory.

The region is the lowest latitude (45 degrees at the southern end) where sea ice regularly forms. Ice cover varies from 50 to 90 percent each winter depending on the weather. Ice often persists for nearly six months, typically from October to March. Aside from the cold winds from the Russian interior, the prodigious flow of fresh water from the Amur River freshens the sea, making the surface less saline and more likely to freeze than other seas and bays.

Map of the Sea of Okhotsk with bottom topography. The 200- and 3000-m isobars are indicated by thin and thick solid lines, respectively. A box denotes the enlarged portion in Figure 5. White shading indicates sea-ice area (ice concentration ⩾30%) in February averaged for 2003–11; blue shading indicates open ocean area. Ice concentration from AMSR-E is used. Color shadings indicate cumulative ice production in coastal polynyas during winter (December–March) averaged from the 2002/03 to 2009/10 seasons (modified from Nihashi and others, 2012, 2017). The amount is indicated by the bar scale. Source: Cambridge Core

Bering Sea Ice is Highly Variable

The animation above shows Bering Sea ice extents at April 2 from 2007 to 2020.  The large fluctuation is evident, much ice in 2012 -13 and almost none in 2018, other years in between.  Given the alarmist bias, it’s no surprise which two years are picked for comparison:

Source: Seattle Times ‘We’ve fallen off a cliff’: Scientists have never seen so little ice in the Bering Sea in spring.

Taking a boat trip from Hokkaido Island to see Okhotsk drift ice is a big tourist attraction, as seen in the short video below.  Al Gore had them worried back then, but not now.

Drift ice in Okhotsk Sea at sunrise.

At  the bottom is a discussion of statistics on year-end Arctic Sea Ice extents.  The values are averages of the last five days of each year.  End of December is a neutral point in the melting-freezing cycle, midway between September minimum and March maximum extents.

Background from Previous Post Updated to Year-End

Some years ago reading a thread on global warming at WUWT, I was struck by one person’s comment: “I’m an actuary with limited knowledge of climate metrics, but it seems to me if you want to understand temperature changes, you should analyze the changes, not the temperatures.” That rang bells for me, and I applied that insight in a series of Temperature Trend Analysis studies of surface station temperature records. Those posts are available under this heading. Climate Compilation Part I Temperatures

This post seeks to understand Arctic Sea Ice fluctuations using a similar approach: Focusing on the rates of extent changes rather than the usual study of the ice extents themselves. Fortunately, Sea Ice Index (SII) from NOAA provides a suitable dataset for this project. As many know, SII relies on satellite passive microwave sensors to produce charts of Arctic Ice extents going back to 1979.  The current Version 3 has become more closely aligned with MASIE, the modern form of Naval ice charting in support of Arctic navigation. The SII User Guide is here.

There are statistical analyses available, and the one of interest (table below) is called Sea Ice Index Rates of Change (here). As indicated by the title, this spreadsheet consists not of monthly extents, but changes of extents from the previous month. Specifically, a monthly value is calculated by subtracting the average of the last five days of the previous month from this month’s average of final five days. So the value presents the amount of ice gained or lost during the present month.

These monthly rates of change have been compiled into a baseline for the period 1980 to 2010, which shows the fluctuations of Arctic ice extents over the course of a calendar year. Below is a graph of those averages of monthly changes during the baseline period. Those familiar with Arctic Ice studies will not be surprised at the sine wave form. December end is a relatively neutral point in the cycle, midway between the September Minimum and March Maximum.

The graph makes evident the six spring/summer months of melting and the six autumn/winter months of freezing.  Note that June-August produce the bulk of losses, while October-December show the bulk of gains. Also the peak and valley months of March and September show very little change in extent from beginning to end.

The table of monthly data reveals the variability of ice extents over the last 4 decades.

The values in January show changes from the end of the previous December, and by summing twelve consecutive months we can calculate an annual rate of change for the years 1979 to 2019.

As many know, there has been a decline of Arctic ice extent over these 40 years, averaging 40k km2 per year. But year over year, the changes shift constantly between gains and losses.

Moreover, it seems random as to which months are determinative for a given year. For example, much ado has been printed about October 2020 being slower than expected to refreeze and add ice extents. As it happens in this dataset, October has the highest rate of adding ice. The table below shows the variety of monthly rates in the record as anomalies from the 1980-2010 baseline. In this exhibit a red cell is a negative anomaly (less than baseline for that month) and blue is positive (higher than baseline).

Note that the  +/ –  rate anomalies are distributed all across the grid, sequences of different months in different years, with gains and losses offsetting one another.  Yes, October 2020 recorded a lower than average gain, but higher than 2016. The loss in July 2020 was the largest of the year, during the hot Siberian summer.  Note November 2020 ice gain anomaly exceeded the October deficit anomaly by more than twice as much.  December added more surplus so that the anomaly for the year was nothing. The bottom line presents the average anomalies for each month over the period 1979-2020.  Note the rates of gains and losses mostly offset, and the average of all months in the bottom right cell is virtually zero.

A final observation: The graph below shows the Yearend Arctic Ice Extents for the last 30 years.

Note: SII daily extents file does not provide complete values prior to 1988.

Year-end Arctic ice extents (last 5 days of December) show three distinct regimes: 1989-1998, 1998-2010, 2010-2019. The average year-end extent 1989-2010 is 13.4M km2. In the last decade, 2009 was 13.0M km2, and ten years later, 2019 was 12.8M km2. So for all the the fluctuations, the net loss was 200k km2, or 1.5%. Talk of an Arctic ice death spiral is fanciful.

These data show a noisy, highly variable natural phenomenon. Clearly, unpredictable factors are in play, principally water structure and circulation, atmospheric circulation regimes, and also incursions and storms. And in the longer view, today’s extents are not unusual.

Illustration by Eleanor Lutz shows Earth’s seasonal climate changes. If played in full screen, the four corners present views from top, bottom and sides. It is a visual representation of scientific datasets measuring Arctic ice extents.

As noted in a previous post, alarms were raised over slower than average Arctic refreezing in October.  Those fears were laid to rest firstly when ice extents roared back in November, and now with the Arctic freezing fast in December. The image above shows the ice gains over the last two weeks, from Dec. 5 to 17, 2020.  In November, 3.5 Wadhams of sea ice were added during the month.  (The metric 1 Wadham = 1 M km2 comes from the professor’s predictions of an ice-free Arctic, meaning less than 1 M km2 extent). So far in December a further 1.9 Wadhams have been added with another two weeks to go in 2020.

Some years ago reading a thread on global warming at WUWT, I was struck by one person’s comment: “I’m an actuary with limited knowledge of climate metrics, but it seems to me if you want to understand temperature changes, you should analyze the changes, not the temperatures.” That rang bells for me, and I applied that insight in a series of Temperature Trend Analysis studies of surface station temperature records. Those posts are available under this heading. Climate Compilation Part I Temperatures

This post seeks to understand Arctic Sea Ice fluctuations using a similar approach: Focusing on the rates of extent changes rather than the usual study of the ice extents themselves. Fortunately, Sea Ice Index (SII) from NOAA provides a suitable dataset for this project. As many know, SII relies on satellite passive microwave sensors to produce charts of Arctic Ice extents going back to 1979.  The current Version 3 has become more closely aligned with MASIE, the modern form of Naval ice charting in support of Arctic navigation. The SII User Guide is here.

There are statistical analyses available, and the one of interest (table below) is called Sea Ice Index Rates of Change (here). As indicated by the title, this spreadsheet consists not of monthly extents, but changes of extents from the previous month. Specifically, a monthly value is calculated by subtracting the average of the last five days of the previous month from this month’s average of final five days. So the value presents the amount of ice gained or lost during the present month.

These monthly rates of change have been compiled into a baseline for the period 1980 to 2010, which shows the fluctuations of Arctic ice extents over the course of a calendar year. Below is a graph of those averages of monthly changes during the baseline period. Those familiar with Arctic Ice studies will not be surprised at the sine wave form. December end is a relatively neutral point in the cycle, midway between the September Minimum and March Maximum.

The graph makes evident the six spring/summer months of melting and the six autumn/winter months of freezing.  Note that June-August produce the bulk of losses, while October-December show the bulk of gains. Also the peak and valley months of March and September show very little change in extent from beginning to end.

The table of monthly data reveals the variability of ice extents over the last 4 decades.

The values in January show changes from the end of the previous December, and by summing twelve consecutive months we can calculate an annual rate of change for the years 1979 to 2019.

As many know, there has been a decline of Arctic ice extent over these 40 years, averaging 40k km2 per year. But year over year, the changes shift constantly between gains and losses.

Moreover, it seems random as to which months are determinative for a given year. For example, much ado has been printed about October 2020 being slower than expected to refreeze and add ice extents. As it happens in this dataset, October has the highest rate of adding ice. The table below shows the variety of monthly rates in the record as anomalies from the 1980-2010 baseline. In this exhibit a red cell is a negative anomaly (less than baseline for that month) and blue is positive (higher than baseline).

Note that the  +/ –  rate anomalies are distributed all across the grid, sequences of different months in different years, with gains and losses offsetting one another.  Yes, October 2020 recorded a lower than average gain, but higher than 2016. The loss in July 2020 was the largest of the year, during the hot Siberian summer.  Note November 2020 ice gain anomaly exceeded the October deficit anomaly by more than twice as much.  The bottom line presents the average anomalies for each month over the period 1979-2020.  Note the rates of gains and losses mostly offset, and the average of all months in the bottom right cell is virtually zero.

Combining the months of October and November shows 2020 828k km2 more ice than baseline for the two months and matching 2019 ice recovery.

The average December adds 2M km2 of sea ice according to SII dataset, and in the first 17 days of December 2020 ice increased by 1.9M km2, with 2 weeks of futher freezing to come.

A final observation: The graph below shows the Yearend Arctic Ice Extents for the last 30 years.

Note: SII daily extents file does not provide complete values prior to 1988.

Year-end Arctic ice extents (last 5 days of December) show three distinct regimes: 1989-1998, 1998-2010, 2010-2019. The average year-end extent 1989-2010 is 13.4M km2. In the last decade, 2009 was 13.0M km2, and ten years later, 2019 was 12.8M km2. So for all the the fluctuations, the net loss was 200k km2, or 1.5%. Talk of an Arctic ice death spiral is fanciful.

These data show a noisy, highly variable natural phenomenon. Clearly, unpredictable factors are in play, principally water structure and circulation, atmospheric circulation regimes, and also incursions and storms. And in the longer view, today’s extents are not unusual.

Illustration by Eleanor Lutz shows Earth’s seasonal climate changes. If played in full screen, the four corners present views from top, bottom and sides. It is a visual representation of scientific datasets measuring Arctic ice extents.