Now let's turn our attention to the last few months and the effects of the SW-ZD on the MIS itself:
Indeed in the MIS the push towards the front is powerful and the problems start when the shear on one edge is not constant, but acts on precise zones and especially when these zones are no longer followed downstream by other zones with a shear of the same magnitude or even a shear zone at all. These shear differentials indeed determine tensions in the MIS that will create rifts that will extend to its center (remember that shear is not limited to the edge, but extends inside).
Image of 24/09/2019: the rifts R3 (downstream of P1) and mR1 (downstream of P2 do not exist yet)
The brake by the Cork on the downstream part of R2 is almost nil, because of its rotary movement, which no longer opposes the movement of the future Iceberg. Hence the rapid widening of R2. But, still because of its progressive rotation, the brake on P0 (the point downstream of P1) is not strong and will weaken later. This will cause, in October, the opening of mR1 in a first time, followed in a second time by the explosive opening of R3 and the entry into sleep of mR1. We can think that the Crescent/Keystone complex brake on P2 was initially stronger than the Cork2 brake on P1, but that quickly the latter, which is downstream, increased its action and became the main braking point of the MIS.
The result can be seen in the image of 23/12/2019.
In the final image of 16/03/2020 we see that P1 is free in its movement and that the action of the downstream brake is of the Crescent/Keystone complex on P2, which can only lead quickly to the calving of P2, which we have just witnessed, and the reactivation of mR2.
Another point to remember, in order to understand the events of this season, is that the edge of the PIG-fed part of the MIS is a point of resistance to the progression of rifts, which can lead to a temporary halt in their progression, or even to the birth of a separate, seamless extension beyond this point of resistance, and possibly to an extension in another direction as mR1 has recently done (in other words: stopping the extension of a rift may not mean that there is no more tension in progress).
In a next post I will analyze the present and the future, but already I invite you not to observe the SW-ZD with all the attention returned to its calving, but rather in the opposite direction: towards its braking action on the MIS, an action that can be extremely destructive.
Click twice to zoom in.