GW: a paper out on the persistent Arctic Cyclone of 2016 that noted its feeding on other warm core lows that entered the basin
That would be:
Extreme Arctic cyclone in August 2016
A Yamagami et al 12 July 2017
http://onlinelibrary.wiley.com/doi/10.1002/asl.757/fullhttp://neven1.typepad.com/blog/2016/08/2016-arctic-cyclone-update-1.html#more http://journals.ametsoc.org/doi/10.1175/JCLI-D-15-0755.1 on summer Arctic Frontal Zone
http://onlinelibrary.wiley.com/doi/10.1029/2012GL054259/full classic GAC 2012 account
"An extremely strong Arctic cyclone (AC) developed in August 2016. The AC exhibited a minimum sea level pressure (SLP) of 967.2 hPa and covered the entire Pacific sector of the Arctic Ocean on 16 August. At this time, the AC was comparable to the strong AC observed in August 2012, in terms of horizontal extent, position, and intensity as measured by SLP.
Two processes contributed to the explosive development of the AC: growth due to baroclinic instability, similar to extratropical cyclones, during the early phase of the development stage, and later nonlinear development via the merging of upper warm cores. The AC was maintained for more than 1 month through multiple mergings with cyclones both generated in the Arctic and migrating northward from lower latitudes, as a result of the high cyclone activity in summer 2016.
The Great Arctic Cyclone of August 2012 is well analyzed as a remarkable summer AC (Simmonds and Rudeva, 2012). They showed that this AC had the lowest central pressure and largest size of any summer AC from 1979 to 2012. Summer ACs have longer lifetimes, are more numerous, and are weaker than those in winter.
Most cyclones in the Arctic during summer are generated over the Arctic Ocean, and most of the remainder is generated over the northern Eurasian continent. In the context of these previous studies, the intensification of AC in August 2016 was unusual for summer.
ACs have warm (cold) core at upper (lower) level and barotropic vorticity in the troposphere. Previous studies showed that the baroclinicity over the Arctic frontal zone was one of the main factors for generation and intensification of ACs. Recently, Crawford and Serreze (2016) indicated that the baroclinicity affected only on an intensification of ACs. The coupling with lower and upper cyclones was also important for the development of ACs....
Features and mechanisms behind the development of the extreme AC of August 2016: The AC16 arose over the Laptev Sea on 4 August and was maintained for more than 1 month through repeated mergings with other cyclones. The AC16 recorded a minimum SLP of 967.2 hPa and covered the entire Pacific sector of the Arctic Ocean.
In addition, the AC16 experienced two notable periods of development after its initial development:
On 15 August, the AC16 merged with a cyclone that originated to the west of the trough over the Scandinavian Peninsula on 11 August. The combined cyclone moved along the northern coast of Eurasia and developed rapidly from 13 to 16 August, with a decrease in central pressure of ∼30 hPa.
The extreme development of the cyclone occurred via two processes: a baroclinic process, as occurs in extratropical cyclones, in the early phase of the development stage and a nonlinear process caused by the merging of the upper-level warm cores in the later phase of the development stage (on 15 August). Simmonds and Rudeva (2012) concluded that not only baroclinicity but also the establishment of a connection with the tropopause polar vortex were important to the development of the AC12. Both processes were also seen during the rapid development of the AC16. Furthermore, our results confirm that a merging of warm cores accelerates the development of the AC16.
The lifetime of the AC16 was much longer than that of the AC12 due to multiple merging events. The merging process is essential to ACs, and it may correspond to the connection between an upper polar vortex and a surface vortex. However, when the cyclones were as strong as the AC16, two vortices were merged with in some cases and not in the other cases. Thus, it is suggested that the occurrence of merging for ACs is not determined by only length scale or strength of cyclones."