Hi there! This is a busy time of year for followers of Arctic sea ice, as we are quickly approaching the annual minimum sea-ice extent. This year’s minimum will probably be set sometime in the next week or so, and I will touch more on it in my blog for next month.
Instead, my blog for August’s ‘climate viz of the month’ will be short and highlight a comparison of the midnight sun in the Arctic and polar night in the Antarctic. Of course, this also relates to the importance of the seasonal cycle in polar regions, like for sea ice and the surface energy budget.
This particular animation is subtle, so watch closely – it shows a view of incoming solar radiation taken at the same time every day (12:00 UTC) from March 21 to September 21. You can clearly see the differences in sunlight for the opposite hemispheres. In fact, we will be approaching the annual maximum sea-ice extent in just a few weeks or less as the austral winter comes to an end. Although most of my graphics focus on extreme events or long-term climate trends, sometimes I think it’s equally as important to step back and just appreciate visualizations showing the seasonal cycles of climate variables. This always helps me better understand the interconnected nature of the Earth system.
While most of my research is related to computer programming – either through climate models, machine learning, or using other statistical tools – I did have the opportunity to visit the Arctic for a summer field school in graduate school. It was by far one of the best experiences of my life, and I will never forget the moment I saw Arctic sea ice for the first time on our icebreaker the R/V Lance. But I must admit, experiencing 24 hours of sunlight was one of the strangest things I’ve ever encountered. I suppose you eventually get used to it, and I am sure it didn’t help that my dorm room had bright red curtains (that were not darkening either) in Tromsø, Norway 🥴. But I can’t wait to go back.
That’s all for now! You can always find my older blogs from this year at https://zacklabe.com/blog-archive-2022/ and the associated climate data rankings at https://zacklabe.com/archive-2022/. Overall, August 2022 was another pretty quiet month in the Arctic compared to some extreme years in the last decade. The largest air temperature anomalies were in the vicinity of the Barents, Kara, and Laptev Seas region, which is likely related to the unusually early sea-ice decline that has become so common anymore in those areas. In fact, in preparing for this year’s Arctic Report Card (which will come out in December 2022), we observed near-record high sea surface temperatures in the Barents Sea this August. Unsurprisingly, the thickness of Arctic sea ice remained well below the 1981-2010 average according to PIOMAS. It will be interesting to extend the new CryoSat-2 summertime observations of sea-ice thickness for this summer. More on this very exciting new research and data product later!
Describing Arctic sea ice can be quite tricky. Scientists have an alphabet soup of terms to describe similar, but different states of the ice. The most common term you are probably used to hearing is “sea-ice extent,” which is also what is displayed on most graphs. Arctic sea-ice extent describes a binary choice for sea-ice cover over a specific region. In other words, if the fraction of a defined box is covered by at least 15% of sea ice then it receives a . This box is now considered completely ice-covered. But if the fraction of ice cover in this box is less than 15%, then it receives a . This box is now considered open ocean water. The area of each  box is then counted up (usually in square kilometers) and the final sum is reported as the total Arctic sea-ice extent. While (by definition) this metric overestimates the actual area of Arctic sea-ice cover – since many boxes are not 100% covered by sea ice – it is a useful, consistent measure for monitoring long-term trends in Arctic sea ice and helps address uncertainties in data like Arctic sea-ice concentration. Some other sea ice terms could include sea-ice volume, sea-ice thickness, sea-ice ice draft, sea-ice area, sea-ice roughness, and sea-ice age, but those are blogs for another day.
Okay, now Arctic sea-ice concentration is actually what I want to highlight for July’s “climate viz of the month.” Sea-ice concentration is that fractional value of ice cover at every grid box that I just described. So it’s totally unitless and usually reported as a percent.
Just as related side note – data derived from satellites are often provided on 2-dimensional spatial grids/maps, where the size of each grid box is dependent on the resolution of the satellite algorithm. Therefore, we can retrieve a fractional sea-ice concentration value at every gridbox (or point) on the map.
I am featuring July’s Arctic sea ice concentration because it provides a clear example on the importance of considering the relationship between local weather conditions and sea-ice variability. While many of us probably think of air temperature as the first thing responsible for changes in Arctic sea ice – warm up, melt down or cool down, freeze up – the mechanisms that affect the variability of Arctic sea ice are much more complicated.
Another side note – that melting could also be coming from the bottom (think warming ocean waters)… More on that later too.
The variability of Arctic sea ice is very much affected by the movement of ice across the Arctic Ocean. This motion can be influenced by large-scale processes, such as ocean currents, but it also can be influenced by storm systems that last only a few days. We often call these Arctic cyclones. In addition to their first order effects of wind, precipitation (rain and snow), and high waves, Arctic cyclones can also affect the surface energy budget through changes to cloud cover and humidity in the lower atmosphere. All these processes contribute as competing mechanisms response for causing sea ice to either melt, grow, expand, or contract. Understanding the role of changes to Arctic cyclones and their influences on Arctic sea ice remains a very active and important area of research. There is no clear consensus on this topic. That is unless you want me to become my nitpicky self and start listing all the uncertainties and methodological choices.
Anyways, now FINALLY getting back to July… Looking at the animation you can see that there is a lot going on in a month’s time (click on it to enlarge). Sea ice is clearly moving around. There are also “flashes” of sea-ice concentration. But these are usually data artifacts resulting from some of those satellite uncertainties I mentioned earlier. Basically, things like cloud cover and melt water on top of the sea ice can interfere with the passive microwave satellite instrument algorithms and subsequent estimates of sea-ice concentration. But the interesting area in July was a region of unusually low Arctic sea-ice concentration close to the North Pole. We can double check with imagery from NASA’S MODIS satellite instrument to verify that indeed there were many areas of open water close to the North Pole. This low sea-ice concentration likely resulted from a series of storm systems in that region that contributed to the ice spreading apart (aka sea ice divergence).
So why? How unusual is this? Well, this certainly isn’t the first time we’ve observed low sea-ice concentration near the North Pole. In fact, the amazing MOSAiC team described large areas of open water near the North Pole surrounded by mushy ice in August of 2020. And 2016 was another notable year of ridiculously low concentration in the northernmost portions of the Arctic. However, there is evidence that this is also becoming more common. Long-term trends reveal substantially thinner and younger sea ice across the entire Arctic Ocean. Sea ice that is thinner can often be more fragile and easily moved around by summer cyclones, like the ones we observed in July. This is shown in July’s visualization where the patches of low sea-ice concentration move around in circular-like motions near the North Pole. Notably, this string of stormy activity in July 2022 over the central Arctic did not result in a large loss of sea-ice extent. In fact, current levels of Arctic sea-ice extent are higher than many recent years (currently the 12th lowest on record as I type this blog). But to be very clear, the Arctic does not at all resemble what it would have looked like in the summertime just a few decades ago. The long-term changes are obvious, despite year-to-year variability.
I can’t help but wonder what this imagery may have looked like with a thicker sea-ice cover, like in the 1980s or 1990s? Would the recent stormy weather have had the same influence? This visualization demonstrates the importance of considering influences beyond temperature that result in changes to Arctic sea ice. Understanding changes in summertime Arctic sea ice is tough. We need to think about thermodynamic (like temperature) and dynamic (like its movement) contributions to understanding why some years experience more melt than others.
Yet I still can’t help but feel unease anytime I see larger areas of open water close to the North Pole.
Thanks for reading! You can find my older blogs from this year at https://zacklabe.com/blog-archive-2022/ and the associated climate data rankings at https://zacklabe.com/archive-2022/. Overall, July 2022 was a pretty unremarkable month for Arctic climate statistics, but there’s always something important if you look a bit more closely.
The first ‘climate viz of the month’ highlights the recent anomalous warmth over northwestern Canada and parts of the Canadian Arctic Archipelago, including Banks Island and Victoria Island. This visualization shows the highest temperature set for each location during the 1-9 July 2022 period.
An anomalous ridge of high pressure, abundant sunshine, and dry weather conditions contributed to surface temperatures rising to over 32°C (~90°F) for some locations just along the Beaufort Sea (Arctic Ocean). For the first time on record, Inuvik, Canada (Northwest Territories) reached over 30°C for three consecutive days in a row (2-4 July 2022). Numerous other locations also set high temperature records during this anomalous stretch of weather at well over 30°C. While the unusual warmth (at the surface) primarily stayed southeast of the Beaufort Sea, temperatures in the lower troposphere (850 hPa) reached near record high levels for this time of year. The low-level warmth and humidity has further contributed to an expanding number of melt ponds across the Beaufort Sea into the Northwest Passage, such as around Cambridge Bay. Although sea-ice extent remains near the 1981-2010 average in the Beaufort Sea, partly due to an arm of thicker, multi-year sea ice, it is likely these conditions have acted to precondition the sea ice for accelerated melting later this summer. Smoke from the extensive wildfires in Alaska and northwestern Canada has obscured some of the view of these melt ponds, but the blue shading to the ice is still visible on MODIS Terra.
Even though current levels of sea-ice extent and thickness are not as low as some recent years, regional extremes, including the wildfires and record warmth in the Canadian Arctic, continue to tell the story of a changing Arctic. I discuss the importance of understanding this interannual variability versus long-term trends in a new blog. Lastly, check out my new archive of monthly temperature and sea ice rankings for 2022 at https://zacklabe.com/archive-2022/.