post discussions about paleo climates and big picture stuff in other threads
Paleo and synoptic have interest per se but are indeed too far afield from the current refreezing season (this forum). The failure of climate models to explain Arctic amplification (despite decades of research and huge longterm data sets) proves that fundamental pieces of the puzzle are not understood. Paleo affirms that previous episodes of relatively warm high northern latitudes ('equable climate') cannot be understood from C02 levels and tropical ocean temperatures alone but we knew that already — it’s in our face every day.
The tipping point for the Arctic occurred at exactly 11 minutes after midnight on a Friday because of a black swan event on 01 Jan 2016. It’s that simple.
Winter storms, large and small, that bring in extra-tropical heat and moisture are understood today as critical contributors to Arctic ice conditions (after reversing earlier gospel about net radiative effects). However these storms are not new — they’re listed by date, duration, and hPa in the refs below — though possibly their frequency or extremity is trending upward. Alternatively, their impact is increasing via synergy with downward trending ice conditions, eg strong winds stir open water to greater depth and cause more mechanical damage to thinner ice.
In any event, it now seems winter is in the driver’s seat. Arctic amplification is timed oppositely from melt season — that’s mostly when we learn the car is in the ditch.
The epic 29-31 Dec 2015 storm event you mention has been discussed here a half dozen times already [Boisvert 2016, Moore 2016] along with six major spring storms unique in their massive in situ documentation (N-ICE 2015). A third paper on that
928 hPa storm has just appeared. Low as that sounds, this was only 4th lowest in the last twenty years of North Atlantic windstorms, though the extremity and duration of its Arctic warming impact was record-setting (58 winter seasons 1958-2015):
Braer 13 Jan 1993 913 hPa
Noname 15 Dec 1986 916 hPa
Dirk 24 Dec 2013 927 hPA
Frank 30 Dec 2015 928 hPa
Vivian 28 Feb 1990 940 hPa
29 Dec 2015 — 06 Feb 2016 40 days
25 Jan 2014 - 17 Feb 2014 24 days
30 Jan 2012 - 20 Feb 2012 22 days
02 Jan 1977 - 20 Jan 1977 19 days
28 Nov 2007 - 16 Dec 2007 19 daysNone of these storms have any discernible connection to sudden stratospheric warming (SSW) events affecting the Polar Vortex; the SSW are listed and animated here:
http://birner.atmos.colostate.edu/ssw.htmlhttp://p-martineau.com/ssw-animations/ It would be interesting however to monitor Arctic effects of the SSW that J Cohen predicts (on 23 Jan 17) for the next two weeks:
https://www.aer.com/science-research/climate-weather/arctic-oscillationMajor cause of unprecedented Arctic warming in January 2016: Critical role of an Atlantic windstorm
BM Kim et al 04 Jan 17
http://www.nature.com/articles/srep40051 free full text, easy read
"In January 2016, the Arctic experienced an extremely anomalous warming event after an extraordinary increase in air temperature at the end of 2015. During this event, a strong intrusion of warm and moist air and an increase in downward longwave radiation, as well as a loss of sea ice in the Barents and Kara seas, were observed.
Observational analyses revealed that the abrupt warming was triggered by the entry of a strong Atlantic windstorm into the Arctic in late December 2015, which brought enormous moist and warm air masses to the Arctic. Although the storm terminated at the eastern coast of Greenland in late December, it was followed by a prolonged blocking period in early 2016 that sustained the extreme Arctic warming.
Numerical experiments indicate that the warming effect of sea ice loss and associated upward turbulent heat fluxes are relatively minor in this event. This result suggests the synoptically driven warm and moist air intrusion into the Arctic was a primary contributing factor of this extreme Arctic warming event....
Despite the importance of the Arctic state for the adjacent mid-latitudes, the major cause of Arctic warming remains a controversial issue. The following factors have been suggested:
1) surface reflectivity of snow and ice
2) oceanic heat loss by surface turbulent heat fluxes
3) incoming longwave radiation emitted by water vapor and clouds
4) surface thermal inversion
5) atmospheric lapse-rate
6) poleward atmospheric energy transport by moisture intrusion
The anomalous warm temperature was maintained during the entire month of January, which produced a record anomalous Arctic-mean temperature. In particular, the SAT locally increased to the extreme value of approximately 30 °C higher than normal in January over the Eurasian Arctic sector.
This event appeared to be super-extreme in the sense that no warming event had developed as rapidly as this event or maintained for such a long period. This case is unprecedented over the available period of modern data...."
Maybe so, but for how long? And how does it compare to cumulative impacts from a steady train of smaller storms bring in extratropical warmth and moisture? How does this storm -- and ones this season -- manifest itself on our favorite products such as nullschool, SMOS, AMSR2, Jaxa, Hycom etc?