Tuesday, March 15, 2016

The Battle of the Bulge

Fig. 1
The Earth bulges at the equator.

It does so to the degree that the planet is twenty six and a half miles bigger-around at the equator than it is at the poles (Equatorial Bulge).

It is like that because the planet is rotating (spinning) at about 1,040 mph, which pulls or pushes ocean water, among other things, toward the equator to produce a bulge (Earth's Rotation).
Fig. 2

Evidently it is not widely known that this rotational dynamic impacts upon sea level change.

For today's post I did some graphs based on sea level change records at or near the equator.

The graphs at Fig. 2, Fig. 3, and Fig. 4 show that significant sea level dynamics take place there.

But, like other places it is not a perfectly smooth globe there, so as graphs in Dredd Blog posts show, sea level change varies from place to place.
Fig. 3

The melt water entering the ocean, and the ghost-water already in the ocean at Greenland, Antarctica, and Glacier Bay for example, are pulled or pushed toward the equator, i.e., toward the bulge.

Not many people know that when melt water and ghost-water leave those areas, the sea level there falls as that water flows in the direction of the Earth's bulge as indicated in Fig. 1 (The Ghost-Water Constant, 2, 3, 4).

In other words, there is a tension between the rotational pull and ice sheet gravity pull that is rarely considered (ibid).

The "point" where the two conflicting pulls equalize is called the "hinge point" or hinge line (The Evolution and Migration of Sea Level Hinge Points).

As the ice sheet loses mass it also axiomatically loses a directly related amount of its gravitational power.

Thus, as the Earth's rotational power becomes predominant and pulls the ghost-water away from the ice sheet area, the sea level falls around the land mass upon which the ice sheet rests (The Gravity of Sea Level Change).

It is quite clear to me that thermal expansion, land subsidence, and the like, are not major players in the sea level change scenario.

They are all minor players in sea level change.

The graphs at Fig. 3 and Fig. 4 show my hypothesis as to what the origins of sea level change are (after fossil fuels are burned).

The primary factor is displacement caused by ice sheet melt and calving as the ice sheet relocates from a land mass and flows into the ocean.

Next in significance is the release of ghost-water which had been held up close to the land mass by ice-sheet gravity.

Last and least is thermal expansion, etc. which is erroneously considered to be a or the major player by many who are unaware of all of the forces at play.

It is about time for the warming science commentariat to get modern.

As soon as they realize that they have been spreading a myth or two around the globe, and stop doing so, we will all be better off for it  (The Warming Science Commentariat, 2).

Their bathtub model myth is not doing anyone any good (The Bathtub Model Doesn't Hold Water).

In the next post or so of this series I intend to use major seaport zones and Antarctica zones (if those zones have tide gauge and other required data) in those zones as readers have requested.


  1. Thanks Dredd!
    Fascinating just to ponder all this. Have also been thinking about the moon /sun influence on tides on top of the displacement of melt water towards the equator; seems likely that latitudes well above and below the zero line will experience sharp SLR too.
    Note: The tides are affected by many things including 'depth' of seas and still the best ways to 'forecast' the tides are through long term record keeping of observations as astronomical measures are imprecise. As my old man used to say, " notes in faded pencil are superior to the best memory."

    1. Mark,

      The Earth's gravity is the moderator that works to spread the ocean water around and about, as it flows toward the bulge. Some of it is relocated all along the way. Not all of it at all gets to the bulge.

      In terms of large areas like zones, SLR happens everywhere SLF does not.

      At individual tide gauge stations both happen with regularity, so the big picture, the truth if you will, is in the trend line.

      Remember too, that like the tides you mentioned, SLR and SLF overcome each other at times.

      Greenland one year might cause 1 mm of SLF while Antarctica might cause 1 mm of SLR at the same site.

      The long term trend presented in the historical record shows clearly this tug and pull, like the tug and pull of tides.

      The SLR and SLF ups and downs are not noticable to the naked eye on a daily basis, compared to the tides.

      But the SLR trend is quite noticeable at high tide in more and more locations every year.

    2. Many thanks Dredd!
      "The SLR 'trend' is quite noticeable at high tide in more and more locations every year."
      Does it ever!
      10 trillion tons of ice coming off Greenland in the last decade and melt rate is 'increasing!'
      Really appreciate your terrific work and share it widely.

  2. Good analysis, Dredd.


    1. That one area had an average of 10.5mm yr for about half a century (Fig. 2).

      They say we have about 3mm yr global average now since about a decade.

      They are missing some ghost-water in the bathtub eh?