The margins are currently set up in the following way:

30000-18000: use the same margin, which is from Ehlers et al (2011).

13000-present: use the same margin, which is simplified from the GLIMS database (Raup et al., 2007).

For the time slices between that, I interpolated between the LGM and modern margin, using Contour Interpolation (https://github.com/evangowan/contour_interpolation). I tried to have it
retreat backwards through deep fjords, so that it is realistic retreat.

I fully intend to replace this with Bethan Davies's margins, as soon as they become available.



Ehlers, J., Ehlers, J., Gibbard, P.L. and Hughes, P.D. eds., 2011. Quaternary glaciations-extent and chronology: a closer look (Vol. 15). Elsevier.

Raup, B., Racoviteanu, A., Khalsa, S.J.S., Helm, C., Armstrong, R. and Arnaud, Y., 2007. The GLIMS geospatial glacier database: a new tool for studying glacier change. Global and Planetary Change, 56(1-2), pp.101-110.

-----------------
2019/05/07
-----------------

For the pre 30000 time slices, I refer to Darvill et al 2017 (QSR). By the sounds of things, the ice sheet remained near maximum through MIS 3, but expanded beyond the MIS 2 limit to reach a maximum extent around 45000-48000 yr BP. In fact, there is no evidence that there was a large extent ice sheet during MIS 4. In New Zealand, there was a maximum about 65000, so it is probable that the ice extent was larger than present.

Note, that it is likely that the ice extent was larger than present throughout MIS 3 due to favourable climatic conditions, so I have used extensive conditions for all of these timesteps. I will likely revise this in far better detail at a later time, especially if Bethan Davies margin reconstructions come out.

Framework:

70000: same as present
67500: same as 15500 margin
65000: same as 17000 margin
62500: same as 17000 margin
60000: same as 16000 margin
57500: There is evidence of an expansion sometime around 56400, I will put it to be equal to the 16500 margin
55000: same as 15500 margin
52500: same as the 15000 margin
50000: same as 15500 margin
47500: same as 17000 margin
45000: In some places in Patagonia (i.e Darvill et al 2015), the last glaciation maximum happened about 45000 yr BP. I set this time to be equal to the LGM margin
42500: same as 17000 margin
40000: same as 17000 margin
37500: there is some evidence that another local maximum happened about 37800, so I use the LGM limit for this time.
35000: same as 17000 margin
32500: same as 17000 margin

-----------------
2019/06/06
-----------------

Added margins for 80000 to 70000, just used the modern outline for this period
