any buttressing effect between the north side and the main glacier? If so, then its receding could help the calving front retreat further.
Yes, depending on the thickness and velocity (~ momentum) of the ice coming roughly orthogonally off the north side, the effect would be to compress the main ice stream to its walls and surface rocks on other side, tending to inhibit motion and calving. The main north branch at one time played this role as did a pinning point mid-fjord. The large bend upstream would have a similar effect. Whether these add up to anything quantitatively is questionable. Really it is the north side that has become uncorked.
Next to nothing is known observationally about the Jakobshavn calving front below the water line (eg, is it vertical to bedrock, inclined, or hollowed out?). Radar has issues in heavily crevassed thick ice by salt water, no one has been able to get close with sonar, seals or submersibles, no disposable probes have been dropped, no drilling is feasible, gravity measurements lack sufficient resolution and unique invertibility, the ice temperature profile cannot be measured, and no helicopter sampling has been done of calved pieces. It's fair to say though that ocean and meltwater are well-mixed by calving turbulence.
Rignot's group tried last August to get a ship into the less active calving fronts of nearby Epiq and Store, pushing small bergs off the half-million dollar sonar with hand-held poles but never got there.
http://news.uci.edu/greenland/Jakobshavn may no longer 'trending' in terms of journal articles per year -- perhaps little more can be done, leaving us in predictive limbo. There are far more papers these days on other West Greenland glaciers, mostly on meltwater effects. I could only locate 3 Jakobshavn articles in the last six months:
Seasonal and interannual variations in ice melange and its impact on terminus stability, Jakobshavn Isbræ
R Cassotto et al.
http://www.igsoc.org:8080/journal/61/225/j13j235.pdf free full
"We used satellite-derived surface temperatures and time-lapse photography to infer temporal variations in the proglacial ice melange at Jakobshavn Isbræ. Freezing of the melange-covered fjord surface during winter is indicated by a decrease in fjord surface temperatures and is associated with (1) a decrease in ice melange mobility and (2) a drastic reduction in iceberg production. Vigorous calving resumes in spring, typically abruptly, following the steady up-fjord retreat of the sea-ice/ice-melange margin. An analysis of pixel displacement from time-lapse imagery demonstrates that melange motion increases prior to calving..."
Oceanic Boundary Conditions for Jakobshavn Glacier. Part I: Variability and Renewal of Ilulissat Icefjord Waters, 2001–14
CV Gladish et al
http://journals.ametsoc.org/doi/abs/10.1175/JPO-D-14-0044.1 free full
"Jakobshavn Glacier, west Greenland, has responded to temperature changes in Ilulissat Icefjord, into which it terminates. This study collected hydrographic observations inside Ilulissat Icefjord and from adjacent Disko Bay between 2001 and 2014. The warmest deep Disko Bay waters were blocked by the entrance sill and did not reach Jakobshavn Glacier. In the fjord basin, the summer mean temperature was 2.8ºC from 2009 to 2013, excluding 2010, when it was 1ºC cooler."
Oceanic Boundary Conditions for Jakobshavn Glacier. Part II: Provenance and Sources of Variability of Disko Bay and Ilulissat Icefjord Waters, 1990–2011
CV Gladish et al free full at ResearchGate
"Jakobshavn Glacier, west Greenland, has responded to temperature changes in Ilulissat Icefjord, into which it terminates. Basin waters in this fjord exchange with neighboring Disko Bay waters of a particular density at least once per year. This study determined the provenance of this isopycnic layer for 1990–2011 using hydrographic data from Cape Farewell to Baffin Bay. The warm Atlantic-origin core of the West Greenland Current never filled deep Disko Bay or entered the fjord basin because of bathymetric impediments on the west Greenland shelf. Instead, equal parts of Atlantic water and less-saline polar water filled the fjord basin and bathed Jakobshavn Glacier...."