EnviroLink Forum

Is sea level rise accelerating?

http://www.skepticalscience.com/sea-lev ... ediate.htm

Figure 4: The linear trends in sea level over 20-year periods, with one sigma error on the trend estimates shown by the dotted lines. From 1963 to 1991, there were a series of volcanic eruptions which caused cooling and hence contraction of the upper ocean. This temporarily slowed the rate of sea level rise.

From this figure we can see that has been an increasing rate of sea level rise meaning acceleration.
Sometimes it helps to put numbers on something to get an idea of what our future sea level will be. Out of the general equation that I am going to use there are several other variables to tease out.
http://en.wikipedia.org/wiki/Acceleration



V = u + at
S = ut + ½ at*2


where
= displacement
= initial velocity
= final velocity
= uniform acceleration
T = time


James Hansen had the discussion of a possible 5 meter/century sea level rise rate. Scary number man. The only model I know of to approach understanding this is a wikipedia constant acceleration model. But it will give an overall picture of what could happen for certain scenarios the scientists are talking about.
What would the acceleration have to be for sea level rise of 5 meters by 2100

I am going to go back to 1870 and include that in the sea level rise by 2100. Sea level has risen 20 cm since about 1870 which is slightly under 8 inches. 5meters - .2 meters = 4.8 meters = 480 cm

S = ut +1/2(at*2)
S = 480cm sea level rise
U = initial velocity = .3cm/year
T = 88 years
A = ?

S = (.3cm/year)(88years) +.5 a(88*2) = 480cm
A =[[ 480cm - .3cm/year(88years)] x 2] / 88*2 = .117cm/year acceleration = 1.17mm/year*2 = 11.7mm/decade*2 acceleration average over the next 88 years.

3.28 feet/meter times 5meters = 16.4 feet

Final velocity at the end of the century.

V = U + AT

V = .3cm/year + .117cm/year*2(88years) = 10.596cm/year velocity = 4.17 inches/year = 41.7 in./decade
If we were to get melt conditions similar to meltwater pulse 1a the sea level rise would have a huge velocity.

http://en.wikipedia.org/wiki/Meltwater_pulse_1A

This has happened in the past just before our present holocene.

Personally I don’t think this will reach this kind of acceleration within this century. Down the road, who knows.

Let’s take some low numbers such as Tim the Plumber has been giving us. Let’s go with 24inches sea level rise by 2100.

24inches x 2.54cm/in = 61 cm
61cm – 20cm = 41cm

S = ut +1/2(at*2)

A =(( S – UT) x 2)/T*2

A = ((41cm - .3cm/yr(88yr)) x 2)/ 88*2 = .00377cm/yr*2 = .0377mm/yr*2

To even get to two feet sea level requires acceleration of a little less than .1mm/year or 1mm/decade.

V = u + at
V = .3cm/yr + .00377cm/yr*2(88) = .632cm/yr = 2.5 inches /decade

In order to reach 24 inches sea level rise since about 1870 we would have 2 times the velocity of today’s sea level rise of .3cm/yr. I believe that this will be a very low outcome of today’s carbon emissions. Interesting thing about this one is that IPCC was calling for 59cm while not modeling ice sheet melt and calving and therefore leaving it out completely. This strongly suggests to me that this is going to be low in reality. A lot of projections are higher than this in the 1 to 2 meter range.

1 meter sea level rise

A =(( S – UT) x 2)/T*2

S = 100cm – 20 cm = 80 cm
U = .3cm/yr
T = 88years

A = ((80cm - .3cm/yr x 88yr) x 2)/88*2 = .01382cm/yr*2 acceleration = .1382mm/yr*2 = 1.3mm/decade*2

We were just a little below this in the last two decades of the twentieth century.

V = u + at
V = .3cm/yr + .01382(88) = 1.52 cm/yr = 15.2cm/decade = 6 inches/decade

All sea ports in the world will have to adjust to rising sea levels. What you will build for at the end of the century has to adapt to a higher sea level later.


2 meters sea level rise

A =(( S – UT) x 2)/T*2

S = 200cm – 20 cm = 180 cm
U = .3cm/yr
T = 88years

A = (180cm - .3cm/yr(88yr) x 2)/ 88*2 = .0397cm/yr*2 = .397mm/yr*2 = 3.97mm/decade*2
V = u + at = .3cm/yr + .0397cm/yr*2(88) = 3.794cm/yr = 37.94cm./decade = 15.9inches/decade

Of course, Hansen only said a 5 meter MSL rise by 2100 was possible, not necessarily probable.
I remember the first book I read on it done by something like 35 scientists in 18 disciplines 1992, had calculated it to be a 23" by 2050. I believe that rise was from the MSL at that time. With the acceleration, that would come out close to Hansen's possibility.
The only adaptation the surviving people can make is to keep moving higher in elevation, whatever the real MSL change is.
It will not be nearly as great a sea level change as at the beginning of this interglacial.
Although there will be plenty of land inundated, it is the lesser of problems from AGW. The effect on food supply will be much greater, along with the effect of aquifers depletion, oil depletion, fisheries depletion, and soil loss.

_________________
"With every decision, think seven generations ahead of the consequences of your actions" Ute rule of life.
“We do not inherit the earth from our ancestors; we borrow it from our children”― Chief Seattle
“Those Who Have the Privilege to Know Have the Duty to Act”…Albert Einstein

If one follows the North Carolina legislature, they may never know. Given the 2010 study that indicated real problems with sea level rise on the coast, they acted quickly and firmly to request the study be repeated and again reported in 2015 to see if there is any change from the 2010 information before they will do anything else. Of course, if one pushes back the decision long enough there is nothing left to do but live with the outcome ... or not.

http://www.ncleg.net/Sessions/2011/Bill ... H819v5.pdf

SECTION 2.(b) The Coastal Resources Commission and the Division of Coastal Management of the Department of Environment and Natural Resources shall not define rates of sea-level change for regulatory purposes prior to July 1, 2016.

_________________
With friends like Guido, you will not have enemies for long.

“Intellect is invisible to the man who has none”
Arthur Schopenhauer

"The difference between genius and stupidity is that genius has its limits."
Albert Einstein

Global warming hasn't even hit its stride yet. I think this is only the beginning. This could get bigger.



http://www.wunderground.com/blog/RickyR ... ourcomment



comment 147

Quoting OldLeatherneck:


It also appears certain that Greenland will have another record melt-year of the Greenland Ice Sheet. If that happens, the models for predicting sea-level rise will have to be adjusted upward. In just the month of June, we have witnessed the following dramatic events on Greenland:

1. Record low levels of the Albedo at all elevations.

http://www.desmogblog.com/black-day-jul ... -ice-sheet

2. Temperatures above freezing for 5 consecutive days at the Summit (Elevation 3200 meters)

http://climatecrocks.com/2012/07/16/gre ... -slightly/

3. Peterman Glacier breaks off an ice island 2X the size of Manhattan. Second major calving event in two years.

4. Major flooding of the Watson River at Kangerlussuag caused extensive damage when melt waters were flowing at 3.5 million liters/sec.

http://blogs.discovermagazine.com/inter ... er-decade/



Sea Level Rise at 20 Inches Per Decade?

by Chris Mooney


According to Joe Romm, blogging a recent Nature study, that’s what’s possible–or at least, it appears to have happened in the planetary past, some 121,000 years ago. The numbers, Romm notes, translate into an 8 foot rise over 50 years.

How could such a quick increase in sea level happen? Well, the collapse of a massive ice sheet might do it. And when might that happen? Nobody knows.

As this discussion underscores, by far the greatest threat from global warming is catastrophic sea level rise. Yet given our current understanding of ice sheet dynamics, it’s also a very poorly understood risk. Still, if there were ever a time to err on the side of caution, this is it. Romm writes:


If sea levels were even 3 feet higher in 2100 (let alone 5 or higher) and rising 1 to 2 inches a year at that point, it would be the single greatest preventable catastrophe in human history.

All those who worry about the risks to the “economy” if we take climate action now, here’s a thought for you: What happens to the economy if coastal cities and major financial centers have to retreat from rising seas?


What surprised me was the sea level rise velocity to get 6 feet by 2100. 6 feet didn't mean much until I put the numbers to it. THis is one of those figures where the reality of a stable society is very difficult, if at all.


2 meters sea level rise

A =(( S – UT) x 2)/T*2

S = 200cm – 20 cm = 180 cm
U = .3cm/yr
T = 88years

A = (180cm - .3cm/yr(88yr) x 2)/ 88*2 = .0397cm/yr*2 = .397mm/yr*2 = 3.97mm/decade*2
V = u + at = .3cm/yr + .0397cm/yr*2(88) = 3.794cm/yr = 37.94cm./decade = 15.9inches/decade