Greenland Ice Sheet Doomed… Once more

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Greenland Ice Sheet Doomed… Again

Guest "Geological Perspective" by David Middleton

CRYOSPHERE RESEARCH UPDATE
An unprecedented ice loss is forecast for the Greenland ice sheet
September 30, 2020

Over the next eighty years, global warming will melt enough ice from the Greenland ice sheet to reverse 4,000 years of cumulative ice growth – with ice loss rates more than quadrupling even the fastest melting rates in the past 12,000 years. These stark conclusions come from new simulations that for the first time correlate current and forecast future ice loss rates. Comparison directly with historical ice loss rates. These latest results are in line with previous research showing that if we continue our current high level of greenhouse gas emissions, we can expect Greenland to become ice-free in just 1,000 years.

(…)

As their simulation ventured into the future, they found that the ice loss rate will likely overshadow anything seen in the past. In a high-emission "business as usual" scenario, Briner and his colleagues show that ice loss could reach 35,900 billion tons per century by 2100, while in a low-emission scenario it is expected to increase to around 8,800 billion tons per century. "It was shocking to see that even with low emissions, ice loss will be faster than in the warmest period of the past," says Briner, whose results are published in Nature.

(…)

Physics world

A read-only copy of the paper is available for viewing … nature.

Basically, RCP8.5 melts all of Greenland's ice within 1,000 years.

Does anyone else pick up a mood that was "there, done"?

perspective

This section was taken from the insignificance of the Greenland ice mass loss in five simple diagrams.

I downloaded and recorded the Climate Reconstruction by Kobashi et al., 2017 from NOAA to assess the context of recent climate change in Central Greenland.

Figure 1. Reconstruction of GISP2 temperature since the glacier radial of the Younger Dryas.Figure 2. Reconstruction of GISP2 temperature since 4000 BC Climate and historical periods from Grosjean et al., 2007.Figure 3. Reconstruction of GISP2 temperature since 1900 AD. RMS Titanic, glacier girl, the ice age is coming? and Summit Station temperatures included for "scale" …

The inevitable conclusion is that if there ever was a climate crisis, it was during the Little Ice Age … It was FRACKING cold then!

How does the recent melt compare to the rest of the Holocene? Short answer: "As always". Vinther et al., 2009 reconstructed the elevations of four ice core locations over the Holocene. The elevation of the two inner ice core locations (NGRIP and GRIP) has hardly changed, while the two outboard locations (Camp Century and DYE3) lost 546 and 342 m of ice, respectively.

Figure 4. Most of the melting since the beginning of the Holocene has occurred on the lower elevation outboard sections of the GrIS – as always. The X-axis is in calendar years AD (BC). Height reconstruction data from Vinther et al., 2009. Map from Weißbach et al., 2015.

Vinthers height reconstruction runs from 11,700 to 40 years before the year 2000. So the last year is 1960.

Based on Mouginot's mass balance estimates, there was very little net change from 1960 to 1995, the starting year for Polar Portal's elevation change maps. I enlarged the elevation change maps and posted the ice core locations on them.

Figure 5. Altitude changes in Greenland 1995-1999 and 2001-2005 (Polar Portal).Figure 6. Altitude changes in Greenland 2007-2011 and 2013-2017 (polar portal).

The scale is in meters per year. Note that the ice height has barely changed in these places. Using my Mark I eyeball, I estimated the annual changes in altitude from 1995 to 2017.

Using the heights from 2009 provided by Vinther, I calculated the heights of the four locations from 11,700 years ago to 2017.

Figure 7. Height of four ice core locations 11,700 years ago up to 2017.Figure 8. Height of four ice core locations from 1900 to 2017.

"As always …"

But, but the Greenland ice sheet is still shrinking! When everything melts, the sea level will rise 7 meters !!!

We petroleum geologists are obsessed with calculating the volume of oil and gas reservoirs, and we spend a lot of time doing things called "Isopach maps" and doing "volumetrics". Fortunately for me, Eric Gaba – Wikimedia Commons user: Sting created an isopacheal map of the Greenland ice sheet.

Figure 9. Isopach map of the Greenland ice sheet (Eric Gaba – Wikimedia Commons user: Sting) (left) and elevation change map (Polar Portal) (right).

Almost all of the most recent thinning takes place in the outboard area of ​​the ice sheet (“As always”). I downloaded a high resolution copy of the Isopach map and digitized the contours using the NeuraMap volumetric analysis software. The area and volume of the Isopach map were consistent with the estimates in USGS Professional Paper 1386 – A, Table 2, page A77.

  • Area: 1,736,095 km2
  • Volume: 2,600,000 km3

I used the 10 m contour as the 0 contour. The area of ​​the 0 m contour was very close to the USGS area.

Contours (noun) km2 morning
3,200 888 219,434
3,000 49.381 12,202,209
3,000 896.1 221,429
2,500 364.162 89.986.345
2,000 723.269 178.723.576
2,000 5.395 1,333,230
2,000 9.186 2,269,815
1,500 1,065,247 263,228,385
1,000 1,347,485 332,970,919
– – 1,737,393 429,319,196

The volume was slightly higher than the USGS estimate; but good in the range of other recent estimates. The USGS cites a reference from 1954 for this number and also Bamber et al., 2011, which estimates the volume at 2,900,000 km3. Bamber then increased his estimate to 2,960,000 km3.

Volumes km3
method On site
Trapezoid 2,980,626
pyramid 2,953,938
TrapPyra 2,961,940
Simpson 2,844,332
3/8 rule 2,725,668
VerticalSlice 2,979,256
step 2,456,431
Average 2,843,170

As can be seen, the estimates for the volume of the Greenland ice sheet vary widely and the methods of calculating the volume give a fairly wide range of results … However, modern climatologists can see annual changes in their mass of 0.015% … Go figure!

This is what happens when I drop the 1,000 m contour 10 m:

Volumes km3
method Lose 10 m
Trapezoid 2,977,601 99.90%
pyramid 2,950,926 99.90%
TrapPyra 2,958,915 99.90%
Simpson 2,844,332 100.00%
3/8 rule 2,725,668 100.00%
VerticalSlice 2,976,230 99.90%
step 2,453,891 99.90%
Average 2,841,080 99.93%

99.93% of the Greenland ice sheet does not melt and / or does not calve in the ocean. The USGS paper states that if the entire ice sheet melted, sea levels would rise 6.5 meters. In the highly unlikely scenario above, sea levels would rise a whopping 4.8mm.

  • 6.5 m * 0.07% = 0.00478 m

What happens if I drop the 1,000 m contour by 100 m?

Volumes km3
method Lose 100 m
Trapezoid 2,947,019 98.87%
pyramid 2,920,467 98.87%
TrapPyra 2,928,333 98.87%
Simpson 2,844,332 100.00%
3/8 rule 2,725,668 100.00%
VerticalSlice 2,945,636 98.87%
step 2,428,207 98.85%
Average 2,819,952 99.18%

That's a little more than 2 inches of sea level rise.

RCP8.5: Junk Science About Steroids

If you check out her work in Nature, you'll find that the nightmare scenarios are all tied to the RCP8.5 model scenario where Doctor Evil melts the ice caps with a space laser.

This section was adapted from: US Climate Resilience Tool Kit: Greenland will remain frozen in 2100 … even under RCP8.5

I came across something very useful yesterday on the US Climate-Resilience Tool Kit page from Climate-Dot-Gov.

Figure 10. CMIP5 Global Climate Change Viewer

The widget generates CMIP5 or PMIP3 model outputs for specific countries and a temperature change map of the world. You can also spit out diagrams of each model. And these outputs indicate actual temperature ranges rather than anomalies.

Since Greenland is a great climate playground, I started playing around with it.

Greenland remains frozen in a RCP8.5 bad science fiction nightmare

The first thing I did was hit Greenland with RCP8.5.

Figure 11. Greenland RCP8.5 1980-2004 vs 2071-2095 -> 5.1 ° C.

While the histogram shows an increase in the average annual surface temperature of 5.1 ° C. It is believed that the Sangamonian (Eeemian) interglacial was at least 5 ° C warmer than today and Greenland retained much of its ice. Most of that 5.1 ° C surge appears to be in winter, however, and the July average temperature is expected to still be below freezing, only 2-3 ° C warmer than the 1980-2004 mean.

Andy May's brilliant analysis of NCA4 showed this picture:

Figure 12. “A comparison of 32 climate models and observations. The observations come from weather balloon and satellite data. The two observation methods are independent of each other and support each other. The plot is according to Dr. John Christy from the University of Alabama at Huntsville (Christy 2016). "

Andy noted the following:

INM-CN4 is tagged and alone tracks observations with sufficient accuracy, but does not predict dangerous future temperatures or significant human impacts on the climate.

This resulted in some standard ad hominem and / or unsupported layoffs from Dr. Christy's work and mockery of INM-CM4. So I downloaded UAH 6.0 and HadCRUT4, and 5 year eluent on the same scale as Dr. Christy's 2016 plot recorded.

Figure 13. HadCRUT4 and UAH 6.0 displayed on Christy 2016.

UAH 6.0 generally records within 0.1 ° C of the average of 3 satellite records closest to INM-CM4. HadCRUT4 draws well below the model mean, which is closest to the only model running hotter than INM-CM4. Note that there isn't much of a difference between HadCRUT4 and UAH 6.0. (0.1-0.2 ° C is not a big difference).

Here are the RCP8.5 and RCP 4.5 outputs for INM-CM4 in Greenland:

Figure 14. Greenland INM-CM4 model, RCP8.5. Greenland was still frozen in 2100 and barely warmer than the coldest part of the Holocene, the Little Ice Age.Figure 15. Greenland INM-CM4 model, RCP4.5. Greenland was still frozen in 2100 and barely warmer than the coldest part of the Holocene, the Little Ice Age.

Both models indicate that Greenland will not be significantly warmer in 2100 than it was in 1850. Almost all of the warming is due to an increase in minimum temperatures.

1850 was very cold by Holocene standards.

Figure 16. Alley rebuilding ends around 1850 … only slightly warmer than the coldest Holocene temperatures.

Where's Inigo Montoya when you need him?

Tip points: "You keep using that (sentence), I don't think it means what you think it means."

The Physics World article closes with this …

Previous research has shown that we have already passed the point of no return for the Greenland ice sheet with no hope of preventing a complete collapse, but Briner and his colleagues are not convinced that this turning point has been passed. “It's clear that we are committed to large ice loss this century, but our simulation shows that as we approach a low emission path as we approach 2100, the rate of ice loss can slow down. It is possible to go to future generations with a healthy Greenland ice sheet, ”he says. Lenton agrees and believes there is still time to act. “Even if tipping points have been exceeded, the relatively slow dynamics of the ice sheet make it possible to temporarily exceed a tipping point of the ice sheet and still restore the situation. To do this, of course, the greenhouse gas level has to be reduced, which requires the targeted removal of greenhouse gases in addition to reducing greenhouse gas emissions. "

Physics world

There you have it … The bear is always out of sight in the forest.

Bonus added

A few weeks ago a huge piece of ice – the same size as the Caribbean island of Montserrat – broke away from northeast Greenland.

Physics world

Montserrat ~ 2 Mahattans

Adapted from: 2012: The Year Greenland Melted (AKA Alarmists Gone Wild) and Manhattan-sized icebergs!

Icebergs the size of Manhattan are insignificant compared to Greenland ice sheets.

  • Manhattan: 34 square miles.
  • Greenland Ice Sheet: 660,235 square miles.

Manhattan = 0.005% of the Greenland ice sheet. 99.995% of the Greenland ice sheet did not take part in this event.

If a Manhattan-sized piece of ice calved into the ocean every year and no snow accumulated in Greenland for 1,000 years, Greenland would lose 5% of its ice cover. A little perspective on Manhattan-sized chunks of ice …

Figure 17. Manhattan-sized ice chunks are insignificant compared to the Petermann Glacier and even less to the Greenland ice sheet.
(Wikipedia and Google Earth)

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