Tuesday, March 17, 2015

Will This Float Your Boat - 7

Fig. 1 Antarctica melt zones (click to enlarge)
Following some new research, I have expanded the scope of the C++ Sea Level Calculation Program.

It now includes all of Antarctica, not just W. Antarctica, as you can see from the graphic to the left.

For consistency I have also updated the dimensions of the four zones of melt for both Greenland (Fig. 3) and Antarctica (Fig. 1).

Since Greenland is the location of 75% of current ice melt that contributes to Global Sea Level Rise (SLR), and since Antarctica is only responsible for 25% currently (primarily from W. Antarctica), E. Antarctica can seem insignificant.

That will change over time, as the graphs later on in this post will show, because, among other things E. Antarctica contains enough ice that if it all melted, it would cause SLR of 212.58 feet all by itself (see Fig. 4).

Lucky for us it is not melting much now, so we focus on W. Antarctica and Greenland in terms of ongoing SLR.

The updates to the software are for not only improved accuracy, but for long term
Fig 2. Detail (click to enlarge)
projections to prove some long term points.

Furthermore, "W. Antarctica" and "E. Antarctica" are somewhat arbitrary descriptions for this context.

For example, W. Antarctica in reality includes the Antarctic Peninsula, however, SLR is often calculated separately for the two.

Add to that the fact that some ice shelfs currently melting cross the E. W. boundary, such as the Ross Ice Shelf and the Fimbulisen Ice Shelf --are technically located in both W. Antarctica and E. Antarctica (see Fig. 2).

So, I use the designations "coastal, inland 1, inland 2, and no melt" (in the software design) to describe melt zones of ice (see Fig. 1 and Fig. 2).
Fig. 3 Greenland (click to enlarge)

After all, the concern is ice melt going into the oceans over a given span of time, and the SLR results of that melt.

The zones have been unified (coastal, inland 1, inland 2, no melt) as have the colors (blue, cyan, yellow, red-orange).

Now, all ice melt on the planet is included in the SLR calculations.

The difficult issues include determining the percentages of ice in each zone of Greenland and Antarctica.

Add to that the difficulty in determining the rate of acceleration of melt in each of those zones over time.

Those difficulties are exacerbated by the fact that those values (amount of ice in each zone and percentage of acceleration of melt) are in constant upward flux.
Fig. 4 USGS Data (click to enlarge)

That is, they are naturally constantly changing from year to year.

So, some of the numeric assumptions in the software must change from time to time, to keep up with real world change.

The volume of ice, potential SLR, and percentages are (see Fig. 4) figures which change too, although the major percentages in "no melt" zones are changing very little at this time.

Fig. 5  (click graph to enlarge)
Fig. 5 is the latest graph using the ~21 cm. SLR since 1750 value, so the graph begins at about a foot of SLR already existing in 2015, which makes the subsequent values much higher, so, for that reason alone they may not match prior graphs.

But more than that, when any melt zone reaches "No Melt" the graph line stops, and that zone no longer contributes any more elevation to SLR.

At least out to 2100 (both Greenland and "Other" non-polar zones do that on this graph).

As a result of using the 1750 to 2014 SLR (~21 cm.) by adding it to the CryoSat-2 data (2014 ice melt in Greenland and Antarctica), the 3ft. SLR projection of the IPCC ("~3ft. SLR by 2100") are passed much quicker now, as noted on the graph.

Notice also that after ~2068 Greenland enters the "No Melt" zone, and therefore adds no more to SLR in this century.

The following interactive map (Fig. 6) shows substantial agreement with the graph (Fig. 5) at the year 2100:

Fig. 6 Interactive Map courtesy of Climate Central.

The next post in this series is here, the previous post in this series is here.

No comments:

Post a Comment