What this thread has named the zone of destruction, ZOD, and the second destruction zone, SDZ, might better be considered as the southern shear margin for the PIIS between the southern ice shelf, SIS and the main ice shelf, MIS, as shown by the first attached image from Shean et al. (2019). Furthermore, it seems to me that the majority of the icebergs in the ZOD came from the calving of the green area in the SIS surrounded by blue basal channel carved by the water circulation beneath the SIS shown in the second attached image, and I believe that the calving of the icebergs from this green area of the SIS is well illustrated by the third gif clip (requiring a click to start) assembled by paolo. Also, I believe that the fourth image (also from paolo) of the SIS-SWT rift can also be seen in the first image, and that as this SIS-SWT rift widens both the SIS and the ice shelf for the SWT will be further destabilized
Shean, D. E., Joughin, I. R., Dutrieux, P., Smith, B. E., and Berthier, E.: Ice shelf basal melt rates from a high-resolution digital elevation model (DEM) record for Pine Island Glacier, Antarctica, The Cryosphere, 13, 2633–2656,
https://doi.org/10.5194/tc-13-2633-2019, 2019.
https://www.the-cryosphere.net/13/2633/2019/Finally, I note that the following linked AGU December 2019 presentation by Karen Alley et al. confirms that basal channels are frequently found beneath the shear margins of fast-flowing ice shelves like the PIIS.
Karen Alley et al (from a presentation at the December 2019 AGU Fall Meeting) discuss how basal channels in Antarctic ice shelves can work to destabilize such ice shelves leading to the type of accelerated calving as we have recently witness for the Pine Island Ice Shelf, PIIS. In my opinion this behavior does not bode well for the stability of either the PIIS or the Thwaites Ice Tongue in coming decades.
C53C-1361 - Direct and indirect impacts of basal channels on ice-shelf stability
https://agu.confex.com/agu/fm19/meetingapp.cgi/Paper/509049AbstractBasal channels are frequently found beneath the shear margins of fast-flowing ice shelves, where thinning due to channel formation likely contributes to reduced buttressing and decreased ice-shelf stability. Basal channels are also commonly found in the middle of ice shelves, particularly in areas where warm water is present. In either case, indirect effects on ice-shelf stability related to changes in buttressing and controls on basal melt rates are combined with direct effects, as stresses imparted by basal channels cause fractures, which may initiate calving events. We show that fractures form in association with basal channels on ice shelves throughout Antarctica, both at shear margins and at mid-shelf channels. Upstream channel growth is associated with channel deepening and the upstream propagation of channel-associated fractures on the Getz Ice Shelf. Because basal channels are widespread on Antarctic ice shelves, it is important to ascertain the balance of direct and indirect basal channel influences on ice-shelf stability and the capacity for basal channel change under evolving oceanic conditions.
PS: I find the posts offered recently in this thread to be helpful in better understanding just how rapidly the PIIS is currently being destabilized.
