But just one event does not a record melting season make. What does make a record melting season, is melting momentum. Here follows a barrage of maps and graphs, with short commentary, to give you an idea of how the 2019 melting season stacks up so far (click on the images for larger versions).

Here's an animation of Uni Bremen Sea Ice Concentration maps showing how it all came about (we even had a great poll on the ASIF to speculate about the date when there would be open water all the way):

Every melting season, the entire North American coast clears of ice at some point, making it possible to sail from Bering Strait to M'Clure Strait (western exit/entrance of the Northwest Passage central route). Back in 2016 , there was a chance of this happening record early, but it didn't pan out. This year it did, four weeks earlier than any other year in the Concentration Maps section of the ASIG. The event was reported by Rick Thoman ( ACCAP ) and Lars Kaleschke ( University of Hamburg ), both providing some great graphs and animations (see here ).

But I want to start off with something else. Almost every melting season is marked by some spectacular event nowadays. From the Great Arctic Cyclone of 2012, the huge cracking event of February 2013, the possibility to sail beyond 85N in September 2014, to the almost circumnavigation of Greenland in August last year. This year, another event has really stood out so far.

Before the latest PIOMAS data are published, somewhere next week, I wanted to present an overview of all the things that have been happening in the Arctic these past couple of weeks, and what they may mean for the outcome of the 2019 melting season. You've guessed it, I'm going to be talking about melting momentum (for those not familiar with the concept, here's the archive ).

We'll have a quick look at May first. May was quite sunny, but at this time of year, clear skies don't contribute as much to melting momentum as one would think. The Sun isn't high in the sky yet, the ice surface is quite white and thus reflective, and temperatures are still relatively low (even if May 2019 was warmest/non-coldest on record for Arctic SAT). In fact, it's cloudy, moist conditions that affect the ice first through melt onset, causing the snow layer on the ice to melt. This then refreezes, but is easier to melt later on, creating the first melt ponds.

The image below shows melt pond fraction for May 2012, 2017, 2018 and this year. These maps are generated by a model that has been developed by David Schröder and other scientists from the University of Reading, and have been a huge help over the years in determining melting momentum:

Caveat: This is a model result, and so the distribution of melt ponds doesn't necessarily reflect reality. Thick lines highlight the region with correlation coefficient (used as weighting factor) larger than 0.1. Reference period is 2005-2014.

One can clearly see that this last May was similar to the previous two years, whereas 2012 already had some melt ponding going on. As always, the big question was whether 2019 would be able to catch up with years like 2007, 2011 and 2012 during this crucial month. This is entirely determined by weather patterns, and so below is a comparison for June, showing surface air temperature (SAT) anomaly and mean sea level pressure (SLP) maps from the NOAA ESRL Daily Mean Composites website (2019 runs up to June 27):

When it comes to air temperatures, 2019 is blowing all the other years out of the water. That relentless heat dome over the Siberian side of the Arctic has simply been merciless, and I would be mightily surprised if June 2019 doesn't turn out to be the warmest on record as well (after May). As for SLP, the other years may show more of a classic Arctic dipole (high pressure over the American side of the Arctic, low pressure over Siberia), but 2019's high pressure area is vast, and coupled with relatively low pressure over the Kara Sea, there's a steep pressure gradient, causing strong winds that a) pull all that warm air over the ice, and b) push the ice towards the North Pole, leaving open water in its wake. This is what we Arctic amateur observers like to call the Laptev Bite.

So, what has been the effect on melt pond formation? Unfortunately, we don't have any direct satellite observations, as melt ponds are hard to assess for sensors. But of course, there's always the good, old eyeball™. When melt ponds start to form, the ice pack slowly turns blue (not everywhere at the same time, of course). 2019 was clearly behind on this front during the first half of the month, but it seems to have caught up by June 29th, as I can't see much of a difference on NASA EOSDIS Worldview images:

We also have two indirect measures that provide some information, relative to other years. The first is SMOS, a satellite that can measure thickness up to 0.5 metres during winter. It can't do so during summer, because wet surfaces confuse the sensor. But wet surfaces are just the thing we want to know about! Over on the ASIF, commenter Steven has created a graph that shows how many beige pixels there are on the Uni Bremen SMOS sea ice thickness distribution map. Beige pixels indicate dry surface, so the lower the trend line, the less dry surface:

This graph is far from perfect, of course, as it is based on measurement errors, but the huge drop around mid-June does corroborate what the eyeball™ had seen: Slow to catch up during the first half of the month, but then a massive discolouration of the ice pack.

The second indirect measure for melt pond formation is compactness. Compactness tells us how compact the ice pack is, in other words, how much open water there is within the ice pack. This open water can really be open water, known as leads. But it can also actually be water on top of the ice, or melt ponds, fooling the sensors into thinking it's open water. All of this open water is counted for area, but usually not for extent, because of the 15% threshold (anything above it is counted as 100% ice for extent). If we divide sea ice area numbers with sea ice extent numbers, we get a percentage. During June most of the open water within the ice pack is caused by melt ponds, so a lower percentage, usually means more melt ponds.

The graph below is made using NSIDC area and extent numbers, provided by Wipneus:

Here too, there's a massive drop, around the time when winds started blowing warm air from Siberia over the ice pack. We see the same on Wipneus' collection of compactness measures (Uni Hamburg, JAXA and NSIDC):

We can safely say that 2019 is in the process of building up enough melting momentum to keep it in the game. In fact, I would dare say that it's going to take some really cold and cloudy weather during July and August to keep 2019 out of the top 3. Because other measures also provide evidence that this melting season is a serious contender.

Take for instance, Albedo Warming Potential, that is closely monitored on the CryosphereComputing website (run by Nico Sun, also known as Tealight on the ASIF). It shows how much heat can potentially be soaked up by open water under clear skies. The upper graph shows the daily anomaly, where 2019 is close to melting momentum champion 2012. The graph below it shows accumulated AWP anomaly, and here 2019 is leading at the moment:

And then, of course, there is SST (sea surface temperature). Let's not forget about SST. Here's a comparison, showing DMI SST anomaly distribution maps around this date, for 2012, 2016, 2018 and 2019. This year is basically leading everywhere, except on the Atlantic front (where PIOMAS says the thickest ice is, relative to other years). Look at all of that heat within the nascent Laptev Bite, and also note how in other years there was still ice along the Alaskan coast. There is none there this year, which means ocean currents can more easily transport heat from the Bering Strait towards the western Beaufort (where multi-year ice goes to die nowadays):

Again, it's going to take some really cold and cloudy weather during July and August to keep 2019 out of the top 3. It happened in 2017 and 2018, when things weren't looking all that great either, but less bad than now. It happened in 2015 and 2016 as well. The following animation of Zack Labe's temperature rank by month shows the spanners in the works of those melting seasons, effectively saving the ice:

The last thing we can do, is have a look at the weather forecast and get an idea of what the first quarter of July has in store. Unfortunately, the weather is not letting up. What we see below in the ECMWF forecast for the coming 6 days (via Tropical Tidbits), is a dipole, albeit not the classic set-up. The good news is that the Laptev Bite may slow down a bit, but the dispersed ice in the Beaufort Sea is going to be pushed back towards the pole, and a tight cluster of isobars on the Atlantic side indicate strong winds that will take care of the sea ice in the Kara Sea, and push more ice towards the Atlantic:

The forecast beyond D6 looks somewhat better, but forecasts in the longer range are very volatile right now. We'll have to see whether this relatively sunny and warm weather continues, or whether cyclones come to disperse the weakened ice pack. Either way, it's not looking too good right now.

In recent years, the Arctic has dodged bullets and cannonballs. It looks like this year, it may have to dodge a nuclear bomb.

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The animation at the top of this blog post is based on this painting by James Tissot, with a hat-tip to A-Team for starting to combine the Arctic with art in symbolic ways, back in 2013. I'll be reporting on PIOMAS next week, as soon as data is updated, but I can't promise I'll be writing a lot beyond that, so be sure to keep an eye on the 2019 melting season thread on the Arctic Sea Ice Forum for near real-time coverage by the community there.