Sea Level Rise: U.S. East Coast (IV)

The 2nd region in my set of U.S. east coast areas (as part of the ongoing series) is the Mid-Atlantic North (MAN), from New York City down almost to Cape Hatteras:

I’ll do as before, namely:

  • Align all tide gauge stations within the region since 1950.
  • Form regional average.
  • Test: is it following a straight line trend?
  • Smooth with a lowess fit
  • Fit piecewise-linear model (choose turning point by changepoint analysis).

    As with the New England (NE) region, the MAN is not rising at a steady rate (i.e. following a straight line), there’s more than that going on. Here are the two trend estimates (lowess smooth in red, piecewise linear fit in blue):

    This piecewise linear fit has its turning point in 1989. The rates (of sea level rise) before and after are estimated at 2.8 +/- 0.9 mm/yr and 5.1 +/- 1.3 mm/yr. We can also compare the rate estimates from the lowess smooth (in red) to that from piecewise linear fit (in blue, which is of course just two distinct rates):

    These rates are higher than we found for NE, both pre- and post-1990. The time series of differences between them shows how they have diverged steadily:

    Tests show no evidence of anything but a straight-line increase in the regional difference, with sea level rising in MAN than in NE by 1.2 +/- 0.2 mm/yr.

    Again, we see that there is acceleration in the tide gauge record from the Mid-Atlantic North (MAN), starting around 1989. We also see a consistently faster rise along the MAN, slowest in NE, which is what is expected if the bulk of the difference is because of glacial isostatic adjustment.

    But those are just two of the four U.S. east coast regions. So … more to come …

    This blog is made possible by readers like you; join others by donating at My Wee Dragon.

  • One response to “Sea Level Rise: U.S. East Coast (IV)

    1. An important point to make is that any negative glacial rebound should be a linear change under the time constraints you are using. The step shows changes in the ocean offshore, partly volume change (warmer temperatures), partly circulation change, and partly release of water from ice sheets.