Sunday, 8 January 2017

Antarctica Larson C ice shelf close to becoming one of biggest icebergs ever - or not

Really? The entire ice shelf? It must be true, if the Christian Science Monitor says so:
Antarctica's Larson C shelf is about equal to the area to the state of Delaware. Its collapse might be imminent. 
JANUARY 6, 2017 —Scientists with the British Antarctic Survey now believe that the fracturing of the Larson C ice shelf from the polar cap is imminent, after a rift in the shelf grew vertiginously in the last month of 2016. 
The thread connecting Larson C to the rest of Antarctica is now just more than 65,600 feet long, surveyors from the Britain’s Project Midas say. 
Apart from the ice shelf being about equal in area to Delaware, not one of the statements is correct. They're not simply misquotes. The BAS scientists believe nothing of the kind - their article is titled Giant iceberg set to calve from Larsen C Ice Shelf, and that the calving is imminent. Surveyors from Britain’s Project Midas believe nothing of the kind either. They wrote: (my bold)
Larsen C Ice Shelf poised to calve
The Larsen C Ice shelf in Antarctica is primed to shed an area of more than 5000 sq. km following further substantial rift growth. After a few months of steady, incremental advance since the last event, the rift grew suddenly by a further 18 km during the second half of December 2016. Only a final 20 km of ice now connects an iceberg one quarter the size of Wales to its parent ice shelf.
No one but a moron could fail to grasp what those articles stated and meant. CSM author David Iaconangelo clearly isn't a moron, but is what might be euphemistically termed "economical with the truth".

Grist isn't much better - an editor retitles a "cross-post" and reorders images with captions removed to give a very different impression to the linked Climate Central article.

"Antarctica’s fourth biggest ice shelf is on the verge of collapse" shrieks Grist. However, the picture at the top of the page

.... is of the Larsen B disintegration in 2002. There's no caption, nor is it referred to in the text. Below the author's name is stated "Cross-posted from Climate Central". That link is to the article by CC author Andrea Thompson, titled Large Iceberg Poised to Break Off From Antarctica. Does she, or any of her quoted sources think "Antarctica’s fourth biggest ice shelf is on the verge of collapse"? No, this is just Grist once again changing a word or two, or misquoting a link or two, to push its catastrophic view of anything that might be remotely connected to what they think is the coming apocalypse. Also, that picture has been cropped to remove a distance scale at the bottom, as the Larsen B was about the size of the piece splitting from Larsen C. The scale might give the game away.  The one in the CC article, is captioned quite correctly The breakup of Antarctica's Larsen B ice shelf as it looked on Feb. 23, 2002. Click image to enlarge. Credit: NASA
The breakup of Antarctica's Larsen B ice shelf as it looked on Feb. 23, 2002.
Click image to enlarge. Credit: NASA

It's not a "cross-post" - Grist has altered the title, removed image captions, and reordered images from the CC article, to create the impression that the images are of Larsen C. Removing captions, editing images, and showing them out of context to create an impression not intended by the original author is more than breaking the rules of attribution, it's fraud.

Unusually, I find the CC article generally factual, informative, and links back up the text, though there are one or two disputed claims.

Author Andrea Thompson headed her article with this close-up image of part of the rift:
A large rift in Antarctica's Larsen C ice shelf, photographed by NASA's IceBridge mission on Nov. 10, 2016. The rift surged ahead by about 10 miles in late December.
Click image to enlarge. Credit: NASA/John Sonntag


In the Grist "cross-post", that image follows a a paragraph about the disintegration of Larsen B, and has the caption "NASA". The intention is now obvious, and totally unforgivable.

On a more factual note, the rift is about 500m (metres, not miles) wide, 350m deep in the centre, and is currently about 80km long, according to Project MIDAS. Some articles say 80 miles, and if the scale on the graphic below, is accurate, 150 km would be more like it. Not that it matters to you maybe, but I'll check. It's not unusual for genuine mistakes to go unnoticed by authors:
Source: Project MIDAS

The graphic is of more than a little personal significance - I was born just about where the second "s" in Swansea is located top right (although Wales is a little further north, and a lot warmer than its position on that graphic.

I've read a few articles that say words to the effect that the rift has just been discovered (where did they get that?), but it's been monitored since 2011.

Even the BBC managed to get it right:

Huge Antarctic iceberg poised to break away 
An iceberg expected to be one of the 10 largest ever recorded is ready to break away from Antarctica, scientists say. A long-running rift in the Larsen C ice shelf grew suddenly in December and now just 20km of ice is keeping the 5,000 sq km piece from floating away.
Larsen C is the most northern major ice shelf in Antarctica.
Researchers based in Swansea say the loss of a piece a quarter of the size of Wales will leave the whole shelf vulnerable to future break-up.
Larsen C is about 350m thick and floats on the seas at the edge of West Antarctica, holding back the flow of glaciers that feed into it.
Researchers have been tracking the rift in Larsen C for many years, watching it with some trepidation after the collapse of Larsen A ice shelf in 1995 and the sudden break-up of the Larsen B shelf in 2002.
They even end the piece with
"We are convinced, although others are not, that the remaining ice shelf will be less stable than the present one," said Prof Luckman.
"We would expect in the ensuing months to years further calving events, and maybe an eventual collapse - but it's a very hard thing to predict, and our models say it will be less stable; not that it will immediately collapse or anything like that."
As it floats on the sea, the resulting iceberg from the shelf will not raise sea levels. But if the shelf breaks up even more, it could result in glaciers that flow off the land behind it to speed up their passage towards the ocean. This non-floating ice would have an impact on sea levels.
According to estimates, if all the ice that the Larsen C shelf currently holds back entered the sea, global waters would rise by 10cm.
All that is very much in the future. There are few certainties right now apart from an imminent change to the outline of Antarctica's icy coast.
"The eventual consequences might be the ice shelf collapsing in years to decades," said Prof Luckman,
"Even the sea level contribution of this area is not on anybody's radar; it's just a big geographical event that will change the landscape there."
Prof. Luckman is one of the Project MIDAS team, based in Swansea. I like very much "We are convinced, although others are not...". It shows some humility, the acknowledgement that it's a personal team view. A good note to end on.

UPDATE 10/1/2017

I've been scanning through articles on the British Antarctic Survey website. I've always thought
the BAS to be a reactionary and somewhat alarmist bunch. I had already noticed this, on the page referenced above:
Glaciologist Professor David Vaughan OBE, Director of Science at British Antarctic Survey, said, “The calving of this large iceberg could be the first step of the collapse of Larsen C ice shelf, which would result in the disintegration of a huge area of ice into a number of icebergs and smaller fragments.
“Because of the uncertainty surrounding the stability of the Larsen C ice shelf, we chose not to camp on the ice this season.  Researchers can now only do day trips from our Rothera Research Station with an aircraft nearby on standby.”
In 2015 they said this:
The team, who continue to monitor the ice shelf closely, predict that a collapse could occur within a century, although maybe sooner and with little warning. A crack is forming in the ice which could cause it to retreat back further than previously observed. The ice shelf appears also to be detaching from a small island called Bawden Ice Rise at its northern edge.
"Within a century" - what's changed in the 19 months since that statement? Prof. Vaughan has dramatically changed his view - back in 2015:
Professor David Vaughan, glaciologist and Director of Science at BAS, says:
“When Larsen A and B were lost, the glaciers behind them accelerated and they are now contributing a significant fraction of the sea-level rise from the whole of Antarctica. Larsen C is bigger and if it were to be lost in the next few decades then it would actually add to the projections of sea-level rise by 2100.
On the same page - "within a century" and "the next few decades". However, contradictions like this aren't unusual on the BAS website. Members have very differing views, and careful reading reveals very different "facts" too. The thickness of the Larsen B shelf, which disintegrated in 2002, is given as 200 metres, and on one page a very unlikely and obviously incorrect 1km. That last article I quoted, actually a press release titled New study shows Antarctic ice shelf is thinning from above and below has this lead-in:
The Larsen C Ice Shelf — whose neighbours Larsen A and B, collapsed in 1995 and 2002 — is thinning from both its surface and beneath. For years scientists have been unable to determine whether it is warming air temperatures or warmer ocean currents that were causing the Antarctic Peninsula’s floating ice shelves to lose volume and become more vulnerable to collapse. This new study takes an important step forward in assessing Antarctica’s likely contribution to future sea-level rise. 
The research team combined satellite data and eight radar surveys captured during a 15-year period from 1998–2012. They found that Larsen C Ice Shelf lost an average of 4 metres of ice, and had lowered by an average of one metre at the surface. 
Lead author, Dr Paul Holland from British Antarctic Survey (BAS), says:
“What’s exciting about this study is we now know that two different processes are causing Larsen C to thin and become less stable. Air is being lost from the top layer of snow (called the firn), which is becoming more compacted — probably because of increased melting by a warmer atmosphere. We know also that Larsen C is losing ice, probably from warmer ocean currents or changing ice flow. 
“If this vast ice shelf — which is over two and a half times the size of Wales and 10 times bigger than Larsen B — was to collapse, it would allow the tributary glaciers behind it to flow faster into the sea. This would then contribute to sea-level rise.”
The Antarctic Peninsula is one of the fastest warming regions on Earth, with a temperature rise of 2.5°C over the last 50 years.
"Air is being lost", "probably because of increased melting by a warmer atmosphere". Here's a plot of the "warmer atmosphere" since 1995:
Larsen C - GISS unadjusted data.


I don't think so. What's amazing, is that many glaciologists and climate scientists never keep up-to-date with the latest data, but rely on published papers, many of which are out of date within a few years. I read something a dated a few weeks ago by a glaciologist, publishing regularly in this field, who cited "the continuing warming on the Antarctic Peninsula". An Ostrich is a large flightless bird, claimed to occasionally put its head in the sand. Some scientists are sightless birds, with their heads continually in the sand. More on the "continued warming" (/sarc off) soon.

Saturday, 7 January 2017

"Assessing recent warming" (2017) put in perspective

ScienceMag (AAAS) published a "rebuttal" of the whole idea of any 21st century pause in global temperature increase a few days ago. The Sceptical blogosphere is awash with indignant posts (and comments) claiming data tampering, or "torturing the data until it confesses". I'm reserving my judgement, except to say that the "pause" has been widely acknowledged by climate scientists, referred to in the last IPCC report (AR5), and concerns surface temperature. The Hausfather et. al. article (not AFAIK peer-reviewed, not that that means much these days) concerns sea surface temperature, a wholly different kettle of fish (I really didn't think of that as a pun, honest!).
ABSTRACT 
Sea surface temperature (SST) records are subject to potential biases due to changing instrumentation and measurement practices. Significant differences exist between commonly used composite SST reconstructions from the National Oceanic and Atmospheric Administration’s Extended Reconstruction Sea Surface Temperature (ERSST), the Hadley Centre SST data set (HadSST3), and the Japanese Meteorological Agency’s Centennial Observation-Based Estimates of SSTs (COBE-SST) from 2003 to the present. The update from ERSST version 3b to version 4 resulted in an increase in the operational SST trend estimate during the last 19 years from 0.07° to 0.12°C per decade, indicating a higher rate of warming in recent years. We show that ERSST version 4 trends generally agree with largely independent, near-global, and instrumentally homogeneous SST measurements from floating buoys, Argo floats, and radiometer-based satellite measurements that have been developed and deployed during the past two decades. We find a large cooling bias in ERSST version 3b and smaller but significant cooling biases in HadSST3 and COBE-SST from 2003 to the present, with respect to most series examined. These results suggest that reported rates of SST warming in recent years have been underestimated in these three data sets.
Here's Figure 1 from the article:


Fig. 1 Comparison of the different ERSSTv3b, ERSSTv4, buoy-only, and CCI SST monthly anomalies from January 1997 to December 2015, restricting all series to common coverage. ERSSTv4 is shown as a broad band for visualization purposes; this band does not represent an uncertainty range. The series are aligned on the 1997–2001 period for comparison purposes. Spatial trend maps are also available in fig. S1, and a similar comparison with Argo data is shown in fig. S2.

What it amounts to, is that the authors have found data series which match their agenda, and found reasons to ignore the other data series which don't. Par for the course these days. As it happens, I've been compiling a set of regional temperature records using GISS data (unadjusted of course), since before Christmas. Just to be different, I'm not ignoring data which doesn't match my agenda, I'm concentrating on large areas of the globe which show interesting results on analysis. More in later posts. For the moment, I thought it might be interesting and amusing to look in detail at the temperature record nearest to President Obama's residence (soon to be vacant for a very short period) and NOAA  headquarters at 1401 Constitution Avenue, Washington DC. The thermometer is at Washington National Airport, just 5km across the Potomac river from NOAA, just inside Virginia.

1880-2016

The 11-year Loess filter shows an uptick around the middle 2000s, after a bumpy "plateau" from 1973. No late 20th C warming evident at all. However, the Loess filter works in a way which includes future change (weighted). If the filter range is constrained to 1880-2009, we get:

1960-2016, Loess range to 2009

Warming began in 2010, after a 27-year "pause". Washington itself would undoubtedly show warming, mostly due to the "Urban Heat Island" effect, but the airport is on the west bank of the Potomac, effectively rural and uncontaminated. A little ironic, that a thermometer just across the river from the nation's capital, seat of a president pledged to "halt global warming" shows no 21st C warming until 2010. The plateau runs from 1974, when he was 12yo - he can't claim responsiblity!

More soon, beginning with Pacific islands. Watch this space.


Thursday, 29 December 2016

"Hotspot of accelerated sea-level rise on the Atlantic coast of North America" - final reality check

Last year I shredded the Sallenger et al. paper "Hotspot of accelerated sea-level rise on the Atlantic coast of North America" here. Now, with updated CGPS data from SONEL, I can finally place the headstone on its grave. South of Boston, the coast is subsiding, and subsiding at a generally increasing rate all the way south to Florida. Sandy Hook, a rather inconsequential spot, which all boat traffic in and out of New York harbour pass with barely a glance, had the honour of being one of the few sites along the NW coast with published GPS data. I say had, because SONEL has carried out a massive update of sites worldwide, adding fairly up-to-date data to many. Sandy Hook now has a downloadable record from 1995 to 2013. The record shows that the downward rate has been increasing from less than 2 mm/year in the late 1990s to over 3 mm/year in the three years 2011-2013. I've used the entire record for station SHK5, 2007-2013, which plots at -2.57 mm/year. The SONEL analysis shows -2.65 mm/year, but I've taken account of a few short-term gaps in the data; I assume they didn't. Here's the SONEL plot:


And mine:

Sandy Hook 1993-2015 (Sea-level satellite era):

The relative rate (relative to the tide-gauge/land) is 5.36 mm/year. Absolute rate (relative to the Earth/Geoid) is 2.79 mm/year. The subsidence rate is almost half the relative rate.

The SONEL plot for New York Battery Park, where both tide-gauge and GPS pillar are located:


The rate during the late 1990s was around -1 mm/year. My analysis:

The chart for New York (Battery Park) 1993-2015:

Relative rate is 3.92 mm/year; absolute rate, allowing for subsidence of 1.93 mm/year is 1.99. The "Hotspot" isn't one of sea-level rise, but one of subsidence. Sallenger et al. were also being somewhat disingenuous when they claimed that the rates of subsidence along the coast "were almost constant", and therefore didn't affect their complex analysis or results. They weren't constant when the paper was written, and the rates are generally increasing over the last 20 years; some very little, some like New York and Sandy Hook, significantly increasing. The "Hotspot" was an artefact of questionable and almost impenetrable analysis, ignoring the inconvenient past, and coastal subsidence.

Note also the obvious cycles which appeared in the record after 1970 - large and small alternating. Sallenger et al. used PSMSL annual average data, and so they wouldn't have been obvious. Take some data and torture it using complex and (to me, impenetrable) statistical techniques I imagine most sea-level experts and authors couldn't fathom, and get the answer you want. What I do know is that those techniques aren't suited to relatively small datasets, which is what you have if you use annual average data. Also PSMSL omit years from annual data, even if just one month is missing. The annual data Sallenger et al. used had quite a few years missing, shrinking their database even further.

Something else Sallenger et al. failed to mention is that a comparable rate of rise occurred before the mid-1950s. Somehow their "long-term" analysis wasn't quite that long:
Trend, in mm/year for 30-year sliding window, end year on x-axis.



The red circle marks 2009, the end year for the "Hot-spot" analysis. It's easy to see the rate of increase was much higher prior to 1953. If the whole record shows an inconvenient truth, just analyse part of it.

Tuesday, 27 December 2016

Vanuatu - something unusual and somehow encouraging

I'm busy updating spreadsheets for Pacific islands, mainly those in the Pacific Sea Level Project of the Australian National Tidal Unit - the straight-up and factual branch of the BOM. I updated Vanuatu last of all, as I'm working in alphabetical order. Here's the chart for the full record from 1993 to last month (November 2016):

The level has dropped to almost exactly what it was in 1993, from a peak in 2008-9. It seems to be a combination of SOI dropping from its high in 2009-10, a drop in sea temperature from 2008, and a rise in barometric pressure after 2011. A change of 1 hPa (=millibar) results in a change of 1cm in sea-level. Higher pressure, lower sea-level, and vice-versa. "Storm-surge" is due to low pressure (and high onshore winds) in a storm system. This is SOI to November 2016:

I'm checking on nearby (well, relatively) stations to see if there's anything remotely similar. I've already checked CGPS station data; here's that for Port Vila; the tide gauge is about 1 km away at the Cruise-ship port.

Source: SONEL

Although the red velocity analysis on the left says "Not robust", there's little change. More later maybe.

Friday, 23 December 2016

The Road to Solar - No, it's a Solar Road!

The sheer stupidity of some people is a constant source of amazement to me. Some bureaucrats and politicians (national and local) have their heads so far up their backsides they can't see the bleedin' obvious. There are quite a few stories on news sites over the last two days, about a project, a very expensive project, to install a "Solar Road". The best quote is from a "green" techno-site engadget -
A French town just installed the world's first 'solar road'
The tiny town of Tourouvre-au-Perche in Normandy, France no longer has to worry about how it will power its street lights. The Sun will handle that.
The link is to a guardian article. There are similar articles in the Daily Mail, Le Monde, and hundreds of others across the world. Street lights - they come on automatically at dusk. Dusk - when the sun has dropped below the horizon. When Solar panels aren't producing any electricity. Not one of the journalists, nor the many commenters on those pages, some of whom were critical of the relatively vast cost of the kilometre-long solar array spotted that it won't be generating any electricity when the street-lights are due to switch on. Simply amazing