Lifting the floor at WUWT, to adapt to sea level rise

Over the last couple of days Anthony Watts has handed his WUWT keys over to Eric "eugenics" Worrall. Eric is giving some advice to people living in coastal areas, particularly those areas where rising sea level is going to have a big impact. (Archived here.)

Eric's advice to WUWT-ers who live on the sea shore, is to raise the floor of your house every twenty years. The WUWT article said that Gavin Schmidt's advice was "whacky".  It's Eric's advice that needs to be "whacked".

Eric read an interview with Gavin Schmidt in the Vancouver Sun and picked out one question to write about. Gavin was asked about the future for waterfront cities like Vancouver. He replied that sea levels aren't going to go down. He also pointed out that there is a huge difference between a rise in sea level of one or two feet a century and a rise of one or two metres a century. Gavin wryly commented that the basement won't be the best place for electrical equipment.

Eric did some arithmetic and discovered that two metres in a century worked out at two centimetres a year. (He's not all dumb.) He figured that it would be okay to just lift the house forty centimetres every two decades.

Two little pigs could do it

I don't know what sort of house Eric had in mind. If the house were made of straw, then lifting it wouldn't be too difficult. If it were made of twigs, then it's a bit more of a challenge but do-able. However, if it were built of bricks, then you'd risk the house cracking and collapsing if you tried to lift it by forty centimetres.

Problems caused by rising seas

One thing that Eric didn't mention was storm surges or sinking shores. It's not just the level of the sea when it's level that causes problems. It's the difference it makes when a high tide coincides with a major storm and washes away beaches, cliffs and buildings.

Eric also assumed that the sea level rise would be steady. It won't. Ice shelves will be eroded and then huge slabs of ice sheets will slip into the sea and melt.

Here's the actual sea level rise since 1992, from U Colorado. It's the average annual rise to 2014:

Data source: U Colorado Sea Level Research Group

Here is what would happen if seas kept rising at the same rate over the next 100 years. It's just the trend extrapolated:

Data source for actual: U Colorado Sea Level Research Group

The chart below compares what Eric Worrall is assuming with the more likely pattern, if seas were to rise by two metres over the next 100 years or so:

Data source for actual: U Colorado Sea Level Research Group

When the ice sheets in Antarctica start shifting into the sea with a vengeance, then it won't happen in a nice steady fashion. There'll be bursts and then a break, then another burst. Probably the same with Greenland - though the big melt from Greenland is expected to start a bit later than that from western Antarctica.

How soon will this happen?

It's hard to say just when the ice sheets in Antarctica will begin to cause a sudden sharp rise in sea levels. As each year passes, there is more evidence that it's not just west Antarctic ice sheets we have to be concerned about. There are signs that eastern Antarctica might start to melt sooner rather than later, too.

There was a new study published in Science a couple of weeks ago, which showed how ice shelves have started melting much more quickly since 2003. The scientists drew a picture to illustrate what is happening:

Schematic diagram of an Antarctic ice shelf showing the processes causing the volume changes measured by satellites. Ice is added to the ice shelf by glaciers flowing off the continent and by snowfall that compresses to form ice. Ice is lost when icebergs break off the ice front, and by melting in some regions as warm water flows into the ocean cavity under the ice shelf. Under some ice shelves, cold and fresh meltwater rises to a point where it refreezes onto the ice shelf. Credit: Helen Amanda Fricker, Professor, Scripps Institution of Oceanography, UC San Diego

In addition to the paper, the authors also wrote an article, because apparently some people got mixed up between sea ice (frozen sea water), ice shelves (floating ice from glaciers sliding into the sea) and ice sheets (on land). The article is very clear, and worth referring people to next time you come across a science denier talking about sea ice in Antarctica.

The paper was about the ice shelves. Ice shelves float on the sea water and are attached to ice sheets on their continental side. They are what slows the ice sheets when they flow into the sea. When they disappear, there's nothing to stop the ice sheets flowing straight into the sea - and that's when the sea level will rise a whole lot more quickly.

The ice shelves are melting faster and faster, most particularly around western Antarctica.  This and other studies also showed how in some areas, the ice sheets themselves are getting more slippery underneath as warm water percolates through them.

In the Amundsen Sea region of West Antarctica:

...Crosson and Getz have lost ~18 and 6% of their thicknesses, respectively, over the 18-year period. If this thinning persists for these two ice shelves, we can expect volume losses of ~100 and 30%, respectively, in the next 100 years. Getz is the single largest contributor to the overall volume loss of Antarctic ice shelves, with an average change of –54 ± 5 km3/year, accounting for ~30% of the total volume loss from the West Antarctic ice shelves (table S1). ...

...For the ice shelves in the AS [Amundsen Sea], observed rates are highest near the deep grounding lines, with lower rates found toward the shallower ice fronts (Fig. 2, table S1, and movie S1). This pattern is consistent with enhanced melting underneath the ice shelf forced by an increased flux of circumpolar deep water (CDW) from across the continental shelf and into the sub–ice-shelf cavity (12, 23, 24). The consequent loss of ice-shelf buttressing from increased ocean-forced melting may have driven the grounding lines inland (25) to a point on a retrograde bed slope at which the marine ice-sheet instability mechanism can take over the dynamics of ice export (7, 26). Hence, observed ice-shelf thinning reflects both ocean-induced basal melting and increased strain rates resulting from faster flows. Our analysis shows that thinning was already under way at a substantial rate at the start of our record in 1994. 

In the Bellinghausen Sea of West Antarctica:

We find the most dramatic thickness reduction on Venable Ice Shelf in the Bellingshausen Sea (BS), with an average (and maximum) thinning rate of 36.1 ± 4.4 (64.4 ± 4.9) m/decade, respectively (fig. S1 and table S1). This ice shelf has lost 18% of its thickness in 18 years, which implies complete disappearance in 100 years.

And overall:

We have shown that Antarctic ice-shelf volume loss is accelerating. In the Amundsen Sea, some ice shelves buttressing regions of grounded ice that are prone to instability have experienced sustained rapid thinning for almost two decades. If the present climate forcing is sustained, we expect a drastic reduction in volume of the rapidly thinning ice shelves at decadal to century time scales, resulting in grounding-line retreat and potential ice-shelf collapse. Both of these processes further accelerate the loss of buttressing, with consequent increase of grounded-ice discharge and sea-level rise.

Below is Figure from the paper, showing the rate of melt at different locations:

Fig. 1 Eighteen years of change in thickness and volume of Antarctic ice shelves. Rates of thickness change (meters per decade) are color-coded from –25 (thinning) to +10 (thickening). Circles represent percentage of thickness lost (red) or gained (blue) in 18 years. Only significant values at the 95% confidence level are plotted (table S1). (Bottom left) Time series and polynomial fit of average volume change (cubic kilometers) from 1994 to 2012 for the West (in red) and East (in blue) Antarctic ice shelves. The black curve is the polynomial fit for All Antarctic ice shelves. We divided Antarctica into eight regions (Fig. 3), which are labeled and delimited by line segments in black. Ice-shelf perimeters are shown as a thin black line. The central circle demarcates the area not surveyed by the satellites (south of 81.5°S). Original data were interpolated for mapping purposes (percentage area surveyed of each ice shelf is provided in table S1). Background is the Landsat Image Mosaic of Antarctica (LIMA). Source: Paolo15

From the WUWT comments

I started writing this article last night. Since then there hasn't been another article at WUWT, so this one was where all the deniers vented their denial - with another 160 or so comments added to the 66 from the first time I archived it. A lot of commenters are of the "stupid" category, doing what stupid people often do, claim that it's the Director of NASA GISS who is "stupid". Yeah, right. The agency that first sent men to the moon stupidly appoints a stupid person to head up one of their most important divisions. Others are variously conspiracy theorists, scientifically illiterate or deliberate disinformers.


ferdberple put up a chart, not of sea level anomaly but of the actual depth of the sea - in metres! and wrote:

April 19, 2015 at 9:53 am
And here is a plot of the official Canadian daily average tides for Vancouver. ZERO TREND going back 100 years. Gavin must be using NASA/NOAA’s politically corrected version. Pretty soon NASA will be able to take advantage of their projected sea levels to sail a boat to the moon.

Oh dear. I've marked on Ferd's chart how much a thousand millimetres is. You'd not see a change of a few millimetres by eyeballing. FWIW, here are charts of the sea level change using Ferd's same data, except it's as an anomaly from the 1911 to 1920 mean sea level - in mm not metres. (It's still a bit early to start measuring sea level rise in metres.)

Data Source: Fisheries and Oceans, Canada

otsar has a solution for brick houses and multi-storey buildings:

April 19, 2015 at 2:43 pm
Knowing that hydraulic fractures less than 2500 feet in depth tend to be horizontal, the sea level rise / subsidence problem can be cured by lifting the ground with hydraulic fracturing using concrete, gravel, or anything that can be pumped and used as a permanent propant.
This idea should make the day for a select few. It actually is not a new idea and has been used in the past such as the tower of Pisa.

Donald A. Neill thinks that someone has a time machine and has traveled to the future and measured future sea level. He wrote:

April 19, 2015 at 1:40 pm
Anyone who elevates model outputs over measured data is not a scientist, full stop. 

Charlie is one of the many conspiracy theorists who hang out at WUWT. He wrote:

April 19, 2015 at 1:38 pm
Well you can get hysterical if you forgot to bring tissues on a camping trip. I’m pretty sure you and many future generations will be ok though. This is not about natural climate change. This is about propaganda tactics for a political ruse. There is a saying in Central America when the clouds get dark and ominous in the afternoon. Es azúcar 

tumpy knows that seas are going to rise, quite a lot. But still thinks Gavin is stupid because he talked about existing homes, not future homes. And about Vancouver (in an interview with the Vancouver Sun), not the UK.

April 19, 2015 at 12:49 pm
Gavin must live in a cave, does he honestly think for a second there are not strict planning controls around floor levels in coastal areas and that engineers are not thinking about sea level rise???

Seriously? In the UK for example, houses MUST be built above the 1 in 200 yr tide level plus climate change (say 0.5m) plus a further amount of freeboard (typically 300-600mm depending on uncertainty). That applies to all new houses, so Gavin, you can sleep at night, the mitigation has been going on for years as no one ever seriously thought a carbon tax was going to stop the sea rising! 

References and further reading

Fernando S. Paolo, Helen A. Fricker, and Laurie Padman. Volume loss from Antarctic ice shelves is accelerating. Science, 26 March 2015 DOI: 10.1126/science.aaa0940

Confused about ice shelf decay and sea ice increase? Explaining Antarctic ice types and their different responses to climate changes. An article by Fernando S. Paolo, Helen A. Fricker, and Laurie Padman on the Scripps Glaciology Group website.

Global warming is here to stay, says NASA scientist (with video) - The Vancouver Sun interview with Gavin Schmidt - including a video


From HotWhopper

• Sea level discussion
• Sea level for dummies - two good videos
• Sea levels and global ice volumes over the past 35,000 years
• Not so fast, WUWT! Antarctica could melt quite quickly.
• Unstoppable meltdown in Antarctica - and at WUWT, with a doozy of chart

There are many more, if you search.