csnavywx

SMB doesn't account for calving and discharge at the periphery, which is significant. Despite the cooler conditions, this surface melt season is still above the 1981-2010 average and with the oncoming melt in the next week or two, it will probably remain so for this season. The 2012 melt season was exceptional and doesn't (yet) represent the norm. When we get to the point where SMB can't crack positive (as it almost did that year), it'll represent the non-viability of the ice sheet in the long term and a permanent shift to widespread net ablation. I suspect that will happen consistently when we lose sea ice in the late summer.

Bluewave, You posted this paper earlier and the post is gone: https://www.nature.com/articles/ncomms14375 I meant to comment on it earlier but ran out of time that day. It's definitely an interesting and concerning paper. I've read it a couple of times before. I'm not sure that's what's going on here, as it seems that most of the cooling was from diabatic heat loss, but the mechanisms mentioned in the paper are definitely a concern down the road. It looks like most of the ones that predict deep ocean convection collapse in the SPG target right around mid-century. The SPG collapse happens almost regardless of emissions path too (happens in 2.6 and 8.5). The fact that only the higher skill models do it and it happens regardless of emissions scenario does set off an alarm bell that they might be on to something. The authors obviously thought so as well. It's interesting that the earlier paper you linked (from 2012) showed some SPG instability that the authors dismissed as a 'freak occurrence'. Perhaps not?

The flip side to this is the fact that the record +AO still isn't enough to get a recovery to pre-2007 levels -- only enough to mostly cover for the higher winter temps. You may be right that when we look back, 2007 may have been the most important point in the entire sequence. I'm sure we'll get to some point where extent drops out rapidly towards zero in late Aug in the future, but the biggest change was probably the Beaufort gyre turning from a nursery for ice to a MYI graveyard. That change looks irreversible at this point.

After digging further, it looks like 2013's SST pattern had more in common with 2009 (i.e. cooler interludes in an otherwise warm phase). The real shift appears to have taken place over the following winter: https://link.springer.com/article/10.1007%2Fs00382-015-2819-3 http://iopscience.iop.org/article/10.1088/1748-9326/11/7/074004 Leads to this paper (both previous papers cited in this one): https://www.nature.com/articles/s41598-017-11046-x The particularly interesting part of that last paper (from 2017) is how deep the strong OHC anomalies extend (down past 1000m). As the paper mentions, it's going to take a lot to erase that:

Also of interest -- the CANSIPS, which showed a slow melt season (via MSLP anomalies) many months ago is showing the same pattern next season already -- with a strong -AO pattern in spring transitioning into another strong +AO summer. It has cold SPG/NATL temps staying in place as it did this year.

The EPS and GEFS out to 10 days show some hefty cold anomalies as well and a pole-centered TPV. This year could certainly make a run at 2013 or even 2009 at this point.

EOSDIS Worldview supports this. The pack looks visually much closer to 2009/2013. There's more ponding than those two years, but less than every other year back to '07. With the upcoming TPV pattern setting in again, this year has a good shot of ending up around 5M, despite the low starting volume. The HADGEM1 paper linked earlier is pretty interesting. They state that they think the SPG weakening is a freak occurrence in the model, but the higher skill-score models tend towards SPG convection collapse a lot more than the CMIP5 median. The result is a stronger version of what we're seeing now, which is a very strong cold SST anomaly south of Greenland. This year has been especially impressive, with -2 to -4C anomalies over the entire SPG region and surrounding areas. Interestingly, the CESM4 shows this stall in temperature in the summer through the late 2020s as well, followed by a relatively rapid increase thereafter. In addition to some of the mechanisms listed in the paper(s) above., I think some of this is also related to increases in snow depth in the surrounding land areas, especially on the Siberian side. These past few much warmer winters have resulted in unusual amounts of snowfall, which have helped retard early season melt-out and peripheral ponding. This is all fairly temporary of course. As long as external forcing continues to increase at the current rate (3-4ppm CO2e/yr), it will eventually overwhelm these other factors and cause the pack to collapse regardless. Still on target for the 2030s, imo, even with a stall through the 2020s.

Strong -AD at the moment with colder temps towards the CAA/Beaufort and blowtorch conditions on the Russian half of the basin. Ponding is getting widespread over there on the latest worldview imagery showing strong melting penetrating pretty deep into the snow-covered areas of the basin. Dprog/dt is characteristically high for this time of the year, but a strong rex block near/over the CAA appears likely to develop soon in conjunction with the Laptev block. Depending on placement, there may or may not be some penetration of strong melt conditions into the heart of the central basin in the next week. The upside is the lack of strong export and relatively cold conditions for the Beaufort and Chukchi (which need a break given the extremely weak ice front in the Chukchi atm).

PDO is neutral this year and may go slightly negative, so I don't think that's going to be as big of an influence. That Atlantic SST pattern is really something else and points towards what bluewave is talking about. Although, that SST pattern is also favorable for periodic rex blocking over or just east of Greenland (towards Iceland) and an enhanced storm track south of Greenland overall (which we may incidentally see some of in the coming week). That also favors keeping troughing near the Kara/Barents area. While this doesn't translate into a 2007/2012 or a mega-dipole type pattern it is warmer than the past few years, contingent on how the Pacific behaves. We'll have to see what kind of ponding the upcoming event on the Pacific side will generate as we're entering the critical period for that area. https://worldview.earthdata.nasa.gov/ is a great tool for looking for the general progress of melt ponding. Last year, the CAB remained snow-covered late into the season, which limited the melt.

Yes, a winter like the last two plus a 2012 or 2007-style melt season would get us pretty close to ice-free conditions by the end of Aug. Need a jump start to the melt season to get it going and we just might get that this year given the forecast over the next two weeks.

This May is shaping up to be much different than anything in the in the last several years. Going to get some early snowmelt and melt pond formation if the D4-10 EPS and GEFS and wk. 1-2 CFS are right. Last year, snowmelt didn't start in earnest in the CAB until early July, which left that sector pretty well protected.

KNHK at 33, Leonardtown at 32. Your thermometer might be a tad high, considering KNHK's sensor is very close to the water.

CC on radar shows pretty steady progress of the snow/sleet line. Should clear the western shores here in the next 60-90 minutes and progress across the bay. Some shallow convection showing up in echo tops already.

Are you getting accretion from that freezing drizzle in Easton? I've noticed the obs have fallen to freezing with some wind there.

To be fair, there's still some uncertainty there (and thus bust potential). It's a fragile setup, though it's getting harder to ignore the chorus of a low tucked in 50mi e of WAL and decent convectively-enhanced banding tomorrow. Only additional problem I see on further analysis is the potential for a later changeover closer to the eastern shore. That warm nose will be resilient for a while until heights crash and lift can act robustly on that layer.

After further review of this morning's satellite, radar and guidance, it's time to bump those totals way up. I'll re-post here in a few, but 6+ looks to be on the table for SoMD and the Ern Shore for sure. There were some hints yesterday about the possibility of the track trending closer and a clean transfer. That seems to be the preferred outcome this morning. In particular, there's now agreement that the H5 and H7 lows will develop just southwest and track just south of the area, with southeasterly and easterly winds at those levels, unlike yesterday, which showed messy and weak flow at that level.

Looks reasonable to me. Better to hedge lower until some of the mesoscale details can be worked out.

Our snowfall down here is going to be completely dependent on how quickly and cleanly the coastal low can spin up. Strong CAA in the PBL will help switch p-types over eventually on Wed. morning, but in order to get decent totals, we're going to have to get into the CCB and deformation zone snows. That's certainly possible in a 12Z Euro or 18Z GFS type setup where the surface low rapidly develops and the mid-level low quickly closes off overhead or just south and allows decently strong lift gets going in the DGZ. However, with marginal surface temps and March sun, we're going to need the rates to produce. If that doesn't happen, it'll be a grass and car topper.

The last two years have seen some pretty stunning winter anomalies. The negative feedback from ice thickness growth hasn't really shown up as a result. There's a recent paper that's somewhat related to this by Cvijanovic and Santer (https://www.nature.com/articles/s41467-017-01907-4), Though the abstract focuses on California rainfall, it shows important global changes as well. It even goes into Antarctic sea ice and responses to that as well. TLDR is while the Antarctic response to AGW has been slow (outside the oceans), the Arctic has not, and the downstream effects as a result have been fairly large. There's an opportunity (as outlined in the paper) for future Antarctic sea ice losses to dampen the Arctic-to-tropical response, but since the Antarctic is (a) slower to react and (b) has less ice to lose overall, we should probably expect more of the same in the future, if not at the same magnitude every year.

Solid storm all around. This storm heralds a pattern change (as the big ones often do) to warmer weather in a few days. The warm-up looks fairly brief, however as the strong -AO pattern looks to rebuild out mid-month. Should bring more chances late this month.

Estimated 6" here as best as I can tell, maybe a bit more, maybe a bit less. Had a solid 3" when I went to bed at 3:00 am before it started blowing around a ton. Have 1-2' snow drifts everywhere. Got fairly close to blizzard conditions at NHK at times (a few obs near gale force sustained and 1/4 mi vis.). Still getting light accumulating snow (occasionally moderate) with good flake size. All dendrites.

2.5" here. Steady moderate to occasionally heavy snow. Getting increasingly wind-whipped and blown. Small to medium sized aggregates (mostly dendrites). Low looks to be tied almost entirely to the coastal front, putting it on the far western side of the envelope. Should keep the snow around longer since it will take longer for the northern stream shortwave to kick this thing out to sea.

Getting a few larger aggregates. Snow is mainly dendrites and stellar plates, with a few columns mixed in. Looks like most of the lift is in the DGZ tonight, which should result in some good snow growth, albeit dry, given the low column temps.

Getting blasted under this new f-gen band. <1/4sm. Small flakes, but tons of them. It's headed up your way, Prince.

Lift associated with coastal front is headed in to the eastern shore. Should be seeing some localized rippage with that.