The 3rd quarter numbers for ocean heat content are in. Needless to say, the trend continues.Both the 0-700 m region and the 0-2000 m region will very likely set records for the year, which is usually the case these days.
Also, an educational center on Fox Island in the Chesapeake Bay is closing due to sea level rise. The Fox Island Environmental Education Center run by the Chesapeake Bay Foundation has been on the island for 40 years, but due to "sea level rise and erosion" protective salt marshes have washed away; they had reduced the impact of wind and waves on the center. "Over the past 50 years, more than 70 percent of the island’s land area washed away."
Fox Island is only about 5 miles from Tangier Island, which is also being lost despite strong denialism there and the promises of President Trump.
Here's a 25-year comparison:
There is a start contrast in google maps between satellite view and maps view. I wonder whether the satellite photo was taken during high tide?
ReplyDeleteGood catch! It didn't even occur to me that the satellite view would depend on the tide....
ReplyDeleteThe daily tide variations at Chesapeake Bay this time of year appear to be about 2 feet or roughly .5-.7 meters.
ReplyDeleteThat is roughly 15 times the sea rise in the last 25 years.
it is hard to see that the rising sea of global warming is a significant contributor to the problem
Sea level rise means the high tides are higher and the low tides are higher. How isn't the problematic?
ReplyDelete"...coastal Virginia has seen the highest rate of relative sea level rise on the whole Atlantic coast, more than 14 inches since 1930"
Chesepauke Bay Foundation
https://www.cbf.org/issues/climate-change/sea-level-rise.html
That''s obviously true. Of course it's a factor.
ReplyDeletebut coastal Virginia has tidal variations of six feet or more.
it's hard to implicate a roughly one foot rise in nearly a century as the major contributing factor.
Land use and drainage would be a more primary important contribution.
The Fox Island people didn't say it was all due to sea level rise, but due to ""sea level rise and erosion." 14" could be the difference if the educational center was originally built to accommodate the high tide level, so a 6' tide becomes a 7' tide. I only know what they said, and I don't see why you want to reject sea level rise as a contributor.
ReplyDeleteAnd sea level rise has barely gotten started....
The key statement here was "Over the past 50 years, more than 70 percent of the island’s land area washed away."
ReplyDeleteTides don't explain that drastic change in 50 years, unless Mr/Ms Anonymous believes that tides didn't exist in 1969. But Neil Armstrong was walking on the Moon that year, so I'm pretty sure tides existed then, just like today.
Anonymous's other excuses -- "land use and drainage" are nearly as irrelevant as tides. There has been no significant change in land use or drainage at Fox Island in the past 50 years. The entire island was protected as an environmental education center for 43 of those 50 years, and before that it was a private duck hunting preserve. There has been no construction or drainage at all.
The difference is that regional sea level is approx. 22 cm higher today than in 1969. For a flat, low-lying island, that makes a lot of difference. Every vertical cm of SLR translates to a much larger horizontal encroachment on the marsh, due to its low gradient.
The direct impact of SLR would account for approx 10-20% of the land lost. The remainder is due to erosion, but much of that is indirectly driven by SLR as well.
This is happening to coastal marshes worldwide, and will accelerate as SLR accelerates.
Final comment:
ReplyDeleteI don't know why you people want to mischaracterize what I say to make your point stronger.
"I don't see why you want to reject sea level rise as a contributor. "
I said of course its a factor (my exact words)That is not rejecting it.
"The direct impact of SLR would account for approx 10-20% of the land lost."
it's hard to implicate a roughly one foot rise in nearly a century as the major contributing factor. (my words)
So in a sense i agree with you.
But you have some sort of emotional response to the view that it is a multifactorial, not a simple problem of SLR.
And sarcastic cracks about Neil Armstrong. Why are those necessary? Why do you feel compelled to do that?
That does not serve the public well
it's hard to implicate a roughly one foot rise in nearly a century as the major contributing factor. (my words)
ReplyDeleteWhat else changed over the period?
Do we know that winds, natural erosion, natural drainage, tectonic patterns and probably ten other things haven't changed?
ReplyDeleteIs there any evidence for that?
ReplyDelete"The **direct** impact of SLR would account for approx 10-20% of the land lost."
ReplyDeleteit's hard to implicate a roughly one foot rise in nearly a century as the major contributing factor. (my words)
No, it's not, for a low-lying island that is primarily marsh. You seem to not grasp that the impact of SLR includes both the **direct** effect (inundation of the existing pre-SLR topography) and the **indirect** effect (increased erosion caused by SLR). The combined impact of these from a foot of SLR on an island whose maximum elevation was near sea level at the start of the rise would be much larger than you are recognizing
But you have some sort of emotional response to the view that it is a multifactorial, not a simple problem of SLR.
No one has offered any evidence for the existence of any factor other than SLR, and SLR (including both direct and indirect effects) can adequately explain most of the loss of the island.
And sarcastic cracks about Neil Armstrong. Why are those necessary? Why do you feel compelled to do that?
Because you mentioned "tides" as an explanation for the loss of 70% of the land area of an island from 1969-present. Tides are caused by the gravitational effect of the Moon, a phenomenon that hasn't changed in the past 50 years while the island has been steadily disappearing.
Do we know that winds, natural erosion, natural drainage, tectonic patterns and probably ten other things haven't changed?
See "Russell's Teapot". You have zero evidence that "winds" have changed in the past 50 years in the central Chesapeake Bay region in ways that would cause an island to lose 70% of its land mass.
And if we're going to play that game, then it's entirely possible that your hypothesized change in winds would be driven by broader-scale changes in circulation since 1970 that would in turn have been influenced by greenhouse gas induced climate change over that period.
This is relevant:
ReplyDelete"Climate warming does not force sea-level rise (SLR) at the same rate everywhere. Rather, there are spatial variations of SLR superimposed on a global average rise. These variations are forced by dynamic processes1,2,3,4, arising from circulation and variations in temperature and/or salinity, and by static equilibrium processes5, arising from mass redistributions changing gravity and the Earth’s rotation and shape. These sea-level variations form unique spatial patterns, yet there are very few observations verifying predicted patterns or fingerprints6. Here, we present evidence of recently accelerated SLR in a unique 1,000-km-long hotspot on the highly populated North American Atlantic coast north of Cape Hatteras and show that it is consistent with a modelled fingerprint of dynamic SLR. Between 1950–1979 and 1980–2009, SLR rate increases in this northeast hotspot were ∼ 3–4 times higher than the global average...."
"Hotspot of accelerated sea-level rise on the Atlantic coast of North America," Asbury H. Sallenger Jr et al, Nature Clim Chg, 2012.
https://www.nature.com/articles/nclimate1597
I downloaded the 2015 lidar elevation data for Fox Island from NOAA Digital Coast.
ReplyDeleteHere is a plot showing the cumulative proportion of the island's land area as a function of elevation (in centimeters) above sea level:
https://i.imgur.com/AUtQGlI.png
The highest point on the island is 60 cm, but 90% of the island's area (as of 2015) is below 25 cm.
Even if there were no acceleration in SLR (spoiler: there will be acceleration), nearly all the island's current topography will be below sea level in 2075.
But that ignores the SLR-driven increase in the erosion rate. I'd like to apply the Bruun Rule here to model the loss of land area as a function of SLR, but it's not a straightforward case.
Based on the 2015 topography, a relative local SLR of 4 mm/yr, and a Bruun value of 17 (on the low end), which I modeled based on local slopes, the island will be down to 3 acres (10% of its current area) in 2050.
So a 90% loss of the remaining land is likely in the next 30 years, due entirely to SLR. If Mr/Ms Anonymous thinks that winds etc. are also contributing to the rate of loss, then that would be additional to what I've calculated here.
tl;dr version -
ReplyDeletePeople (in general, not just Mr/Ms Anonymous) tend to greatly underestimate the impact of sea level rise on flat, low-lying coastal areas.
The loss of 70% of the land at Fox Island over the past 50 years is entirely explainable by sea level rise, and nearly all of the remaining land will disappear in the next 30 years, even with no increase in the rate of SLR.
Just not as simple you make it out be, no matter how you cavil:
ReplyDeletehttps://pubs.usgs.gov/circ/1392/pdf/circ1392.pdf
I downloaded the 2015 lidar elevation data for Fox Island from NOAA Digital Coast.
ReplyDeleteHere is a plot showing the cumulative proportion of the island's land area as a function of elevation (in centimeters) above sea level
That is really cool. What did you use to process the data? Excel?
Layzej, I used QGIS to make a histogram of the island's elevations (but it could easily be done in Matlab, R, Python, or whatever). I then pasted the histogram into Excel to make the chart.
ReplyDeleteLikewise, for estimating and applying the Bruun Rule, I first made a map of what would still be above water level (after a 14-cm rise in 2050) based on the existing topography, then calculated the mean slope and estimated the post-adjustment recession distance R due to erosion, applied that distance as a buffer around the post-inundation land/water interface, and pulled the shoreline inward, then calculated the resulting land area.
Interestingly ... of the 90% of the land that will be lost by 2050, 17% (of that 90%) will be due to the direct inundation, and 83% due to subsequent erosion as the slope adjusts.
That 17% is pretty much in line with my totally off-the-cuff estimate a few posts back that of the 1970-present land loss, "10-20%" would have been due to the direct effect. Not bad!
Interesting. Thanks!
ReplyDeleteYou definitely need to control for tide in photos like this. It's like glacier photos, needing to be all during the same time of year, to compare over the years.
ReplyDelete