Cool Trends Persist

Cooler than normal temperatures have persisted recently in both southern and northern Alaska, and a quick glance at UAF's statewide temperature index confirms the decidedly chilly nature of this month for the state overall.  Indeed, the month-to-date average of the UAF index suggests this is the coolest May since 2012, and it might be the coolest since 2001 when the final numbers come in.

It's rather notable that Utqiaġvik hasn't yet reached 32°F this year, and if it happens today or tomorrow it will be the latest since 2001 or 2000.  If Utqiaġvik manages to get into June without a 32°F reading, it will be the latest since 1955.

Here's a map view of the temperature anomaly in the past 30 days, as estimated by ERA5 and ECMWF model data:

Note that the anomaly is expressed in terms of standard deviations, which gives a good sense of how unusual the situation has been: for example, 1.5-2 standard deviations cooler than normal in the vicinity of Cook Inlet.  The standard deviation is calculated for the same 30-day window as the anomaly calculation.

Here's the 500mb height anomaly from the same perspective:

Here's the link to view these graphics for yourself: it's a page that I put together recently.

https://s2s.worldclimateservice.com/wcs/era5_monitoring/

Clicking on the 2m temperature map near Utqiaġvik produces a similar chart to the first one above (confirming the veracity of the model data), but the chart also appends the latest (00UTC initialized) ECMWF ensemble forecast.  Cooler than normal conditions appear likely to persist on the North Slope in the next week or two.

Interestingly, the forecast suggests the 30-day temperature anomaly is likely to become rather strongly statistically significant to the north of Alaska in the coming days:

A caveat is in order, however: part of this anomaly could reflect a discrepancy between ECMWF's current forecast model and the much older model version that is used for the ERA5 reanalysis (historical baseline).  Many tweaks and upgrades have been made by ECMWF since the ERA5 version was implemented, and the new model may have cooler 2m temperatures over Arctic sea ice at this time of year.  We'll find out in a few weeks when the ERA5 data includes these dates and we can do the apples-to-apples historical comparison.

Nevertheless, the forecast does show a robust trough over the Arctic waters to the north and northeast of Alaska, so persistently below-normal temperatures are certainly plausible.

Arctic Sea Ice Update

Notwithstanding very abundant sea ice in the eastern Bering Sea this winter, Arctic-wide sea ice is now vying with 2019 for record-low extent at this time of year; it has been running near the bottom of the "pack" (pun intended) since November.  The following chart provides a comparison to 2019 (the previous record low at this date), 2012 (the year of the record low in September), and last year.

Deficits relative to the 1981-2010 normal are widespread across the marginal seas of the Arctic:

It's an interesting question as to whether the developing big El Niño episode will have a positive or negative effect on Arctic sea ice this summer.  Several of the strongest El Niño events of recent decades developed in parallel with substantial year-on-year declines in Arctic sea ice extent, so the risk of another major drawdown would seem to be elevated.  Here's a scatterplot of year-on-year change in September ice extent versus the June-August Niño3.4 SST anomaly; the notable recent years are 2023, 2015, 2002, and 1997 (lower right quadrant).

However, it's equally clear that there is actually not much correlation overall between year-on-year ice change and the phase of ENSO during summer.  In particular, pre-1997 El Niño events didn't have a consistent relationship with ice changes, and many stronger La Nina summers show modest ice declines rather than gains.

For a bigger picture, here's the correlation of June-August detrended SSTs with the year-on-year ice change:

The colors indicate the SST anomalies that would normally be associated with an increase of sea ice.  Clearly, the North Atlantic and North Pacific have more correlation than the tropical Pacific, but this doesn't imply causation; the SST patterns revealed here may simply reflect the impact of circulation patterns that affect sea ice extent.  Nevertheless, it's interesting to observe that a negative PDO pattern (like recent years) tends to favor higher sea ice extent, and that's confirmed in a scatterplot - although the correlation is not statistically significant:

The atmospheric anomalies themselves show a greater connection with sea ice change, of course; but those anomalies are relatively unpredictable at seasonal time scales.  A positive Arctic Oscillation, for example, slows the summer ice melt, whereas a negative AO phase tends to bring a reduction in ice extent.

ENSO does tend to be inversely correlated with the AO phase in summer, so it's more likely than not that we'll have a negative AO pattern this summer, i.e. more high pressure over the Arctic (and favoring warm and dry conditions in much of Alaska).  This points toward greater sea ice loss, as in other recent El Niño summers; but time will tell if this year fits the same pattern.

Sea Ice Update

The extreme cold over southern Yukon is making headlines at the moment - and deservedly so, given how persistent it is - but for balanced perspective it's also worth considering the remarkable warmth in the Arctic in recent months.  Rick Thoman notes in his latest post that Arctic sea ice extent is running at a record low for the time of year, as it has been since late November:

https://alaskaclimate.substack.com/p/winter-solstice-2025-arctic-sea-ice

Zack Labe's splendid graphic highlights the anomaly:

The largest deficits are found to the east and north of Svalbard, where ice-free waters extend to nearly 85°N, according to the NSIDC analysis.  This is pretty remarkable in late December:

It might be counter-intuitive given the preponderance of cold in Alaska, but Bering Sea ice is also below normal, mostly because of ice deficits in the central and western Bering Sea.  There is pretty good ice cover to the east of St Lawrence Island:

The warm anomaly in the Arctic has been ongoing since the height of summer.  Of course most recent years have been warmer than earlier decades, but the latter half of 2025 has been particularly unusual:

Wind Trends

In last week's post, I noted that Alaska's 10-year running mean precipitation is at a record high, reflecting the fact that the state's climate has become generally wetter in recent decades.  It's common knowledge that temperatures have also increased on a timescale of several decades, especially in the Arctic.  But what about wind?  Are there any notable multi-decadal trends in wind speed for Alaska?

The question of climate trends is not as straightforward for wind, because there is no good long-term "ground truth" data for wind speeds; measurement practices have changed too much over the years.  We have to rely on retrospective estimates from a model, which in my case means the ERA5 reanalysis from the European modeling center.  So take the following results with a pinch of salt.

First we can observe that last year was apparently the windiest year in many decades for Alaska as a whole (according to ERA5); and it was particularly windy over western regions:

This wasn't just caused by one windy month; 6 of 12 months saw statewide winds at least 5% above normal, and January and August were particularly windy.  Only one month - September - was notably calm compared to normal.

Does this reflect a long-term trend towards greater winds?  No: ERA5 data indicates no significant trend over Alaska's land area, and if anything it suggests an absence of windy years in the last 20-30 years.  2024 was quite anomalous compared to the previous couple of decades:

Here's a look at the 75-year change in annual mean wind speed, using a linear trend, and including 2024:

The results in the complex terrain of southern Alaska are highly variable and probably not representative of the actual trends at populated valley-level locations.  (The ~30km horizontal resolution of the ERA5 data is far too coarse to handle complex terrain.)  There's a marginal hint of decreasing wind speeds across parts of the interior, but clearly the model shows increased wind speed across the near-coastal waters of the Bering Sea as well as more widely in the Arctic Ocean.

The seasonal breakdown of the trends shows a few interesting results - see below.  First, the largest percent increase in wind for the Bering, Chukchi, and Beaufort Seas is found in winter, although the Arctic waters have also become more windy in summer and autumn, if the model is to be believed.  The winter trend of increasing wind is also evident across the western land area and the northern interior.  However, it seems that the North Slope and the northern interior have become less windy in autumn, and there is a distinct trend toward less windy summers in the southwestern interior and Bristol Bay region.

The rising wind trends over the Arctic and Bering waters may have more than one cause.  First, there seems to be a trend toward greater storminess over the Bering Sea in winter; the two maps below show the multi-decadal difference of 500mb heights (top) and MSLP (bottom) for 1950-1990 versus 1991-2024.  This is consistent with the December-February wind increase extending inland across northwestern Alaska and the northern interior.

But the general warming trend in the Arctic is also a direct cause of rising wind speeds across the Arctic waters, because the surface-based temperature inversion has weakened, allowing more atmospheric momentum to mix down to the surface.  This effect is pronounced in autumn, when sea ice loss has been dramatic (see the Sep-Nov map above).  Here's a paper from last year on this topic:

https://www.nature.com/articles/s43247-024-01428-1

As for the summer wind decrease in southwestern Alaska, this is probably related to increasing high pressure and fair-weather "ridging" over the Bering Sea at that time of year.  In contrast, the Arctic Ocean seems to have become more stormy, especially in the Eastern Hemisphere.

So far this year, we've seen a very windy January - one of the windiest on record statewide (2024 was the windiest) - but February and March were somewhat less windy than normal.  It will be interesting to see if we have another windy summer, following last summer's record high wind statewide.  I see some reasons to believe the high-latitude summer patterns could indeed be similar to last summer - but more on that another time.

Arctic Ice and Temperatures

Last week I mentioned that Bering Sea ice managed to reach near-normal levels this winter despite relatively warm conditions.  The January-March average ice extent was only slightly below the normal of recent decades, continuing the recovery from the very low ice conditions of (especially) 2017-18 and 2018-19.

The Arctic-wide seasonal sea ice maximum was likewise higher than in most recent years, as documented by Rick Thoman on his blog:

https://alaskaclimate.substack.com/p/march-2024-arctic-sea-ice-update

The relatively abundant ice cover is perhaps consistent with the fact that while tropical and mid-latitude temperatures were extremely elevated in recent months, the Arctic did not see quite the same magnitude of warmth that it did during and after the last big El Niño in 2015-16.  Last time around it seemed that the intense El Niño kicked off a several-year period of really excessive warmth in the Arctic, but so far that hasn't happened with the latest (now dissipating) El Niño.

Here's a simple depiction of mid-latitude versus high-latitude temperature trends in December through February, according to the ERA5 reanalysis:

In the mid-latitude sector from 30-60°N, the winter's average temperature was the second highest on record, behind only 2019-20; but for 60-90°N the winter wasn't quite as warm as the three winters from 2015-16 to 2017-18.

Here's a map comparison of this winter (below, top) with the record warmest winters in the mid-latitude (middle) and high-latitude (bottom) sectors.

Clearly the 2017-18 winter had a very strong Arctic focus of unusual warmth, while it was a colder winter in many mid-latitude locations, at least over the continents.  The Arctic was colder in 2019-20 , but there was extreme warmth across Eurasia as a result of a strongly positive Arctic Oscillation (low pressure over the Arctic, and strong circumpolar flow).

In contrast to both of those years, this winter saw very widespread unusual warmth from the tropics to the Arctic.  Below-normal temperatures at high latitudes were largely confined to certain land areas (Greenland, Scandinavia, parts of Russia, and of course some of Alaska), while air temperatures over the Arctic Ocean were significantly above normal.

Given the very modest reduction in the Arctic's warmth this winter, the recovery in sea ice is interesting and, I think, a little surprising.

Kaktovik Wind

Blizzard season is off to an early start in Alaska's capital for that kind of thing: Kaktovik, on Alaska's eastern Arctic coast.  Snow has been flying since Thursday morning, and winds increased to 50 mph yesterday evening (with gusts to 60 mph).  Thanks to reader Mike for bringing this to my attention.

October is rather early for this kind of weather in Kaktovik, and it's been more than 10 years since such high winds were observed in October.  In winter proper it's more common, with more than 5% of days seeing sustained winds over 45 mph in November through February.

Here's the meteorological setup: high pressure over western and central Alaska, and a deep low pressure system over Banks Island (as of 4pm AKST yesterday).  My clumsy annotation shows the direction of the strong pressure gradient, and Barter Island's location is indicated with the red dot: click to enlarge.

Subsea Cable Fixed

Good news this week for many residents of northern and western Alaska: the Arctic undersea fiber optic cable that was damaged back in June has been repaired, allowing internet and phone service to get back to normal.  This is a story I've been following, because the cable was apparently severed by ice scouring on the sea bed about 35 miles north of Oliktok Point, just up the coast from Prudhoe Bay.  Read more here:

https://alaskapublic.org/2023/09/19/northern-alaska-cable-break-repaired-after-14-weeks-of-internet-outages/

https://alaskapublic.org/2023/06/12/cut-cable-causes-weeks-long-north-slope-northwest-alaska-internet-and-cellphone-outages/

The aspect I find interesting here is that the break occurred in water "about 90 feet deep", and it seems remarkable to me that Arctic sea ice could ever reach the ocean floor at that depth.  Frankly I was skeptical to begin with, thinking that either the depth was misquoted, or that the cable was damaged for some other reason.  But Quintillion's webpage confirms "ROV inspection shows 20 meters of accessible cable on the seabed floor. The target is 50-60 meters of accessible cable in order to reach the surface with workable slack for splicing operations. The water depth in the area is ~25 Meters."

The second article linked above cites Quintillion's president with the following explanation:

“It’s in an area where the land-fast ice and the sea ice kind of meet,” he said. “And so ice scour – which is essentially moving ice hitting the land ice and then (sinking) kind of like a tectonic plate – I suppose that it scarred the seabed floor, and then went down below the depth where we were buried.

(end quote)

It seems that a large wind stress event would be needed to drive sea ice down to such a great depth, so it's worth looking at the weather data.  As it happens, there is some evidence of high winds on June 11, the date the damage occurred.  The following chart shows hourly 10m wind speed from the ERA5 reanalysis at 71°N, 150°W, which is very close to the stated location of the event:

According to the ERA5 data, the wind speed peaked on the afternoon and early evening of June 10, from a direction just slightly north of easterly.  The peak sustained wind speed is not particularly high - less than 30mph - but the ERA5 wind speeds can't necessarily be taken at face value.  The Deadhorse ASOS reported sustained winds of 30-35mph, with higher gusts, at the same time, so the winds may have been somewhat higher over the ice (and there was still 100% ice cover at that time).

To put the peak ERA5 wind in context, I pulled out ERA5's maximum hourly wind speed for the month of June in past years at the same location.  Since 2000, nearly half of all years have seen a June wind speed higher than this year's event, so it really doesn't stand out as an unusual event.

Here's the surface analysis chart for the same time, 4pm AKDT on June 10, courtesy of Environment Canada; click to enlarge.  There's a modest pressure gradient across the near-coastal waters north of Alaska, consistent with brisk easterly winds, but again nothing especially unusual.

It seems that further analysis of the event would require information about ice thickness and motion in the area, and perhaps satellite imagery would reveal the ice subduction process described by Quintillion.

Any sea ice experts care to weigh in?

Arctic Sea Ice Loss Revisited

An interesting study was published last week on the topic of Arctic sea ice loss, led by Igor Polyakov of UAF.  Here's a write-up from the Geophysical Institute:

https://www.gi.alaska.edu/news/new-research-points-mechanisms-atlantification-arctic-ocean

The thrust of the paper is that a change in the Arctic atmospheric circulation has contributed to the lack of sea ice loss since 2007, when the seasonal minimum reached its first dramatic record low.  Since then, Arctic sea ice has been relatively stable, and the new work suggests this is because the new wind patterns have been transporting more fresh water into the Pacific side of the basin.  Fresh water is less dense than salt water and resides immediately under the sea ice, and it serves to insulate the ice from warmer ocean water that would otherwise tend to melt the ice from below.

The following figure from the paper shows the rather surprising hiatus in sea ice loss (based on September ice extent), and the inset map shows the change in upper ocean "available potential energy", which signifies the quantity of fresh water at the surface.  The change to more fresh water and more stable conditions is largely found in the Beaufort and northern Chukchi Seas.

The paper presents a variety of oceanographic analyses to support the hypothesis about redistribution of fresh water into the Pacific sector, and the basic idea seems plausible to me.  However, to throw in my own two cents, I also think it's likely that a portion of the fresh water volume increase has arisen because of greater precipitation and greater river inflows in the past 15 years.

Let's illustrate these two additional factors.  First, it's well-known that the Arctic hydrological cycle is intensifying in response to rapid warming, and the 2021 NOAA Arctic Report Card highlighted the increase in Arctic river discharge, particularly for Eurasian rivers (providing the bulk of Arctic Ocean inflows):

Here's the link:

https://arctic.noaa.gov/report-card/report-card-2021/river-discharge/

The total discharge of all rivers to the Arctic Ocean is estimated to be approximately 5000 km³/year, which is equivalent to about 35 cm of fresh water depth over the entire Arctic Ocean area - but much of this water will reside close to the continents or be transported into the Pacific sector and the Beaufort Gyre, where salinity is low:

It seems plain that an increase in discharge will tend to fortify the fresh water layer in the Pacific/Canada sector of the ocean, especially with the more favorable wind circulation of recent years.  The percentage change in river flows evidently isn't large, but the recent effect may have been magnified by the change in transport patterns.  Here's a diagram of ocean and ice transport around the basin, from Polyakov et al:

The other factor may be increased precipitation.  Ground-truth precipitation measurements are very scarce and uncertain, of course, so here's the ERA5 reanalysis estimate of annual precipitation change between the two 15-year periods that are compared in Polyakov et al.

An increase of 5-15% is widespread across the Asian side of the Arctic Ocean, according to the model.  How much does this amount to?  The annual mean precipitation is very low, only about 250-300 mm (10-12 inches) across much of the area where the increase has occurred:

But in the northern Barents Sea, where annual precipitation is higher and the percentage increase has been large, the absolute increase amounts to 50-100 mm/year.

Interestingly, the total Arctic Ocean fresh water input appears to be roughly evenly split between the average ~35cm depth of river discharge and the average precipitation of about 20-50 cm.  (Some of the snow will evaporate, of course, but some of it melts in summer and feeds the surface fresh water layer.)  With both fresh water sources producing higher volume in recent years, it seems this has probably contributed to the build-up of fresh water and thereby to the longevity of Arctic sea ice.

The question remaining in my mind is how long can sea ice melt be postponed by these mechanisms in the face of rapid atmospheric (and presumably ocean subsurface) warming?  Polyakov et al suggest that the atmospheric circulation regime of the last 15 years is likely to reverse back to the opposite phase very soon, which would be unfavorable for sea ice and perhaps bring about another rapid decline.  It does seem unlikely that sea ice will hold on much longer, unless something very unexpected happens.  Courtesy of Zack Labe's website, Arctic temperatures are on a steep uptrend, including since 2007:

But time will tell, and I imagine that a few more surprises lie ahead.

July Climate Data

August is rapidly advancing, but for the sake of posterity, here's a look back at July.  The high-latitude circulation pattern was dramatically different from earlier in the summer, and Alaska was primarily influenced by a strong ridge to the east and northeast rather than a persistent trough over the Bering Sea.

The big ridge over Arctic Canada produced some extraordinary warmth, including by far the warmest calendar month on record at Inuvik.  Utqiaġvik also had its warmest month on record, narrowly beating July 2019, and on the other side of the pole it was the warmest month ever measured at Barentsburg on Svalbard.  The maps below show monthly mean departures from normal in absolute terms (top) and in standard deviations (bottom).

The monthly ERA5 and NOAA/NCEI data sets both show the very unusual (locally record) warmth across eastern Alaska and the North Slope.  The ERA5 reanalysis indicates that it was significantly cooler than normal for the southwestern mainland and northwest Gulf coast, but this isn't supported by the NCEI data.  Checking in on data from Bethel and Anchorage, the month was in fact cool enough to fall into the lower third of the 30-year climate distribution at both locations, so ERA5 seems preferable.

The state as a whole eked out another month of above-normal precipitation overall, but not by much, and there were big contrasts between wet in the southwest/west/northwest versus dry in the central interior and Southeast Alaska.  The dry conditions in the interior set the stage for the late-season uptick in fire activity; Rick Thoman notes that Delta Junction had its driest June-July period on record, and evidently this trend is still persisting.

As for wind in July, the high-latitude blocking produced a much more stagnant pattern than in June, with relatively light winds across the North Slope and northern interior, but it was windier than normal in the southwest.  And sunshine was yet again lacking for the southwestern mainland and south-central Alaska: it's been a miserable time for sun-seekers down there this summer.

And in a comment for later elaboration: El Niño continues to develop in the tropical Pacific.  The SST pattern looks very El Niño-like already, but the atmospheric component of the phenomenon is having a difficult time getting its act together.  It will be interesting to see if this dichotomy continues.