Thursday, October 1, 2015

New Type of SLC Detection Model - 6

Fig. 1 a section of the "np" zone
Today I want to discuss some strange tide gauge data from the "np," or north polar zone.

It could mean that gravity loss is like ice sheet loss in the sense that it does not take place uniformly.

For example, if a section of an ice sheet melts or calves into the sea in one area of the ice sheet, that mostly affects the gravity in that area.

Fig. 2 red square is where history/future meet
The example of that scenario I want to talk about today, is the tide gauge in  Reykjavik, Iceland.

First, notice the "np" area east of Greenland, and mostly north of Europe (Fig. 1).

Then glance at the graphs one would likely expect for tide gauges in the "np" zone (Fig. 2 - Fig. 5).
Fig. 3
 These are at latitudes and longitudes in the "np" zone, specifically they generally lie to the north of Europe in Norwegian areas. 
Fig. 4

Areas where sea level fall (SLF) is expected as the Greenland ice sheet melts and calves into the sea.

That notion is shown in Fig. 7 where the ice-sheet-mass loss leads to SLF (dark blue area around Greenland).

But, we must not forget that these are not single events taking place in a vacuum.

Fig. 5
No, all of the ice sheets are melting, calving, and having their own particular impact on sea level change (SLC), whether their impact is sea level rise (SLR), or is SLF instead.

I think the jaggedness of the graph lines is indicative of the push and pull, ebb and flow, between and among the different ice sheet locations.

The big players are, of course, Greenland and Antarctica, however, yesterday we saw that local ice caps and glaciers in Alaska have a large impact on SLC there, even dominating the picture.

That scenario is also likely happening in some of the other ice cap and glacier areas in the "np" zone.

If you will notice Fig. 8, and focus on the bottom graphic, it displays several similar locations for Glacier Bay type activity.
Fig. 6

One such area is Svalbard (Wikipedia), another is Iceland (Wikipedia), and yet another is Norway (Wikipedia).

The take-home from this is "be careful to consider all of the influences" in areas where several local contributors are involved.

Greenland and Antarctica are not the only games in town when we look at local or regional areas.

Again, that was made clear yesterday, in the post showing the strong influence of a local cryosphere area on both SLF and SLR (Proof of Concept - 3).

Fig. 7
Now, with that in mind let's talk about Reykjavik (Fig. 6), noticing first that the red square separates the historical, official record from the software model that projects a conservative future SLC ("Dredd's IPCC clone").

(Probably a wrong projection.)

It is in an area where Greenland, Norway, Svalbard, and its own ice cap and glaciers exert influence.

I put a blue line on the track which begins at the year 1957, where the RLR millimeter scale level was 6996, and extended it over to 1995, when the sea level was 7000 (4 millimeter difference).

I drew another line at the 2014 red square, where the history of that tide gauge ends in this graph, then over to where the millimeter level is 7153 (153 millimeters difference, which is ~4.5 inches).

Contrast that with Skagway's ~4 feet of SLF (Proof of Concept - 3) and we can say that on the local scene, things happen very differently in locations with different significant influences.

Reykjavik is surrounded by influences coming from the north, south, east, and west.

Its jagged and abrupt historical track is indicative of a volatile area:
Michael Mann of Penn State and Stefan Rahmstorf of the Potsdam Institute
Fig. 8
for Climate Impact Research say that to see a pattern like this, in an otherwise record hot year, is a sign that the Atlantic ocean’s so-called “meridional overturning circulation” or AMOC — which is driven by differences in ocean temperature and salinity in the North Atlantic — may be slowing down.

Indeed, they say this fits nicely with a study they published earlier this year, which found an “exceptional” slowdown in the circulation over the course of the last century, and suggested that the dramatic melting of Greenland, by injecting large volumes of freshwater into the ocean, may be the cause.

So are they right?
(Everything you need to know about the surprisingly cold ‘blob’ in the North Atlantic ocean). There is still some uncertainty about the cause or causes of the cold blob up there near the tip of Greenland, south of Reykjavik.

Currents and water temperature also have an effect on SLC, so this current Reykjavik anomaly needs to be looked at from several angles.

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


  1. As usual with system dynamics, "it's complicated." Teasing out the various influences won't be easy, so i appreciate your work on this Dredd. Just being able to see the various trends is most helpful, but i realize that a local weather disruption (like, oh, say, a hurricane or typhoon) can have a momentary impact and make these projections vary somewhat at a particular time.


    1. Tom,


      One thing that adds comprehension to the Reykjavik graph can be deduced from Fig. 8.

      Two of the three graphic scenarios in Fig. 8 put Reykjavik in an SLR zone (as Fig. 6 would have it).

      One is Antarctica's influence (Fig. 8- the topmost graphic scenario), the other (Fig. 8 - bottommost graphic scenario) is ice cap and glacial influence from locations near it (Norway, Svalbard, and Finland).

      Since the Greenland influence is the one that indicates SLF, the eastern part of the ice sheet of Greenland is likely not melting and calving as much as the western part of ice sheet is.

      That is one reason a long history of tide gauges helps to clarify the many dynamics ongoing there.

  2. The big picture is that most seaports, coastal communities, and coastal populations are in the "eq" SLR zone.