Archives par mot-clé : Greenland

climate-debate

Geoscientists discover mechanisms controlling Greenland ice sheet collapse

by University of South Florida (USF Innovation), July 19, 2019 in ScienceDaily/Nature

 

Greenland’s more than 860,000 square miles are largely covered with ice and glaciers, and its melting fuels as much as one-third of the sea level rise in Florida. That’s why a team of University of South Florida geoscientists’ new discovery of one of the mechanisms that allows Greenland’s glaciers to collapse into the sea has special significance for the Sunshine State.

New radar technology allowed geoscientists to look at Greenland’s dynamic ice-ocean interface that drives sea level rise.

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Earlier this spring, NASA scientists reported Jakobshavn Glacier, which has been Greenland’s fastest -thinning glacier for the last 20 years, was slowing in its movement toward the ocean in what appears to be a cyclical pattern of warming and cooling. But because Jakobshavn is still giving up more ice than it accumulates each year, its sheer size makes it an important factor in sea level rise, the NASA scientists maintain.

“Our study helps understand the calving process,” Dixon said. “We are the first to discover that mélange isn’t just some random pile of icebergs in front of the glacier. A mélange wedge can occasionally ‘hold the door’ and keep the glacier from calving.”

Journal Reference:

  1. Surui Xie, Timothy H. Dixon, David M. Holland, Denis Voytenko, Irena Vaňkov�. Rapid iceberg calving following removal of tightly packed pro-glacial mélange. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-019-10908-4
climate and geology, climate-debate

Scientist Spots High Geothermal Heat Flux In East Greenland – ‘Dramatic Consequences For Ice Basal Melting’

by K. Richard, July 5, 2019 in NoTricksZone

Geothermal heat flux can foment upper mantle temperature anomalies of 800–1000 °C, and these extreme heat intensities have been found to stretch across 500 km of central-east Greenland. This could result in “a significant contribution of ice melt to the ice-drainage system of Greenland” (Artemieva et al., 2019).

Evidence of more than 100,000 formerly or currently active volcanic vents permeate the Earth’s sea floor (Kelley, 2017).

Active volcanoes spew 380°C sulfuric acid and “metal-laden acidic fluids” into the bottom waters of the world ocean on a daily basis. In other words, literal ocean acidification is a natural phenomenon.

The carbon dioxide concentrations present in these acidic floods reach “astounding” levels, dwarfing the potential for us to even begin to appreciate the impact this explosive geothermal activity has on the Earth’s carbon cycle (Kelley, 2017).

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better to know...?, climate-debate

More than 50 newly discovered lakes beneath the Greenland Ice Sheet

by Lancaster University, June 26, 2019 in ScienceDaily

Researchers have discovered 56 previously uncharted subglacial lakes beneath the Greenland Ice Sheet bringing the total known number of lakes to 60. Although these lakes are typically smaller than similar lakes in Antarctica, their discovery demonstrates that lakes beneath the Greenland Ice Sheet are much more common than previously thought.

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Dr Stephen J. Livingstone, Senior Lecturer in Physical Geography, University of Sheffield, said:

“The lakes we have identified tend to cluster in eastern Greenland where the bed is rough and can therefore readily trap and store meltwater and in northern Greenland, where we suggest the lakes indicate a patchwork of frozen and thawed bed conditions.

“These lakes could provide important targets for direct exploration to look for evidence of extreme life and to sample the sediments deposited in the lake that preserve a record of environmental change.”

climate and geology, climate-debate

How geologic forces are melting southern Greenland ice sheet

by J.E. Kamis, May 25, 2016 in ClimateChangeDispatch

The most plausible scenario for southern Greenland’s surface ice melt is related to geologically induced heat flow and not atmospheric warming for various, well-established reasons. Based on research by the National Oceanic and Atmospheric Administration (NOAA) (see here), the top surface of southern Greenland’s ice sheet is currently melting at a high rate and therefore greatly reducing surface ice volume. They attribute this geographically localized melting effect to an unusually persistent and man-made atmospheric high pressure system (a so-called “Omega Block“) that has remained stationary above southern Greenland during the spring of 2016.

This non-moving high-pressure system has trapped a cell of very warm air above southern Greenland resulting in higher-than-normal surface ice melting rates and volumes. NOAA and the mainstream media are portraying this above-average melting as undeniable proof man-made global warming damaging our planet.

This portrayal is vastly misleading.

That’s because southern Greenland’s surface ice melt is more likely caused by natural, geologically induced heat flow from one of Earth’s largest Deep Ocean crustal plate junctures, the 10,000 mile long Mid-Atlantic Ridge (MAR). The Mid-Atlantic Ridge is “an immensely long mountain chain extending for about 10,000 miles (16,000 km) in a curving path from the Arctic Ocean to near the southern tip of Africa. The ridge is equidistant between the continents on either side of it. The mountains forming the ridge reach a width of 1,000 miles.”

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climate-debate

Greenland ice loss projections are clouded by clouds

by Brooks Hays, June 24, 2019 in UPI

June 24 (UPI) — Predicting where, how and how quickly Greenland’s ice will melt is difficult. Projections by the best models are cloudy, and new research suggests clouds are doing the clouding.

Currently, models of Greenland’s melting ice sheet put the greatest emphasis on the impacts of greenhouse gas emissions. But new research, published this week in the journal Nature Climate Change, suggests the microphysics of clouds are equally important.

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Under high emission scenarios, the uncertainties of Greenland ice sheet models are caused almost entirely by the uncertainties of cloud dynamics.

Cloud cover dictates the ice sheet’s longwave radiation exposure. When clouds over Greenland are thicker, they operate like an insulating blanket, encouraging longwave radiation and surface-level melting.

climate-debate

If “Greenland is catastrophically melting”, how do alarmists explain NASA’s growing Greenland glacier?

by A. Watts, June19, 2019 in WUWT

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It turned out to be a weather event, unrelated to “climate change”. The next year, there was no “insta-melt“.

In fact. we’d not even know about the melting in Greenland before satellites came on the scene. So how many times in the history of the Earth has Greenland has a quick melt spike? I’m guessing hundreds of thousands of times.

Jakobshavn Glacier in western Greenland is notorious for being the world’s fastest-moving glacier. It is also one of the most active, discharging a tremendous amount of ice from the Greenland Ice Sheet into Ilulissat Icefjord and adjacent Disko Bay—with implications for sea level rise. The image above, acquired on June 6, 2019, by the Operational Land Imager (OLI) on Landsat 8, shows a natural-color view of the glacier.

Jakobshavn has spent decades in retreat—that is, until scientists observed an unexpected advance between 2016 and 2017. In addition to growing toward the ocean, the glacier was found to be slowing and thickening. New data collected in March 2019 confirm that the glacier has grown for the third year in a row, and scientists attribute the change to cool ocean waters.

June 6th, 2019 Jakobshavn Glacier in western Greenland . Image acquired on June 6, 2019, by the Operational Land Imager (OLI) on Landsat 8, shows a natural-color view of the glacier.

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climate-debate

Greenland Glaciers Growing Again

by P. Homewood, May 22, 2019 in NotaLotofPeopleKnowThat

European satellites have detailed the abrupt change in behaviour of one of Greenland’s most important glaciers.

In the 2000s, Jakobshavn Isbrae was the fastest flowing ice stream on the island, travelling at 17km a year.

As it sped to the ocean, its front end also retreated and thinned, dropping in height by as much as 20m year.

But now it’s all change. Jakobshavn is travelling much more slowly, and its trunk has even begun to thicken and lengthen.

“It’s a complete reversal in behaviour and it wasn’t predicted,” said Dr Anna Hogg from Leeds University and the UK Centre for Polar Observation and Modelling (CPOM).

“The question now is: what’s next for Jakobshavn? Is this just a pause, or is it a switch-off of the dynamic thinning we’ve seen previously?”

The rapid flow, thinning and retreat of Jakobshavn’s front end in the mid to late 2000s were probably driven by warm ocean water from Disko Bay getting into the fjord and attacking the glacier from below.

The phase change, scientists think, may be related to very cold weather in 2013. This would have resulted in less meltwater coming off the glacier, which in turn might have choked the mechanism that pulls warm ocean water towards Jakobshavn.

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climate-debate

Greenland Has Been Cooling In Recent Years – 26 Of Its 47 Largest Glaciers Now Stable Or Gaining Ice

by K. Richard, May 20, 2019 in NoTricksZone

A new analysis of recent trends for the Greenland ice sheet reveals that since 2012 there has been an abrupt slowing of melt rates and a trend reversal to cooling and ice growth.
• In 2018, 26 of Greenland’s 47 largest glaciers were either stable or grew in size.
• Overall, the 47 glaciers advanced by +4.1  km² during 2018.  Of the 6 largest glaciers, 4 grew while 2 retreated.
• Since 2012, ice loss has been “minor” to “modest” due to the dramatic melting slowdown.
• Summer average temperatures for 2018 were lower than the 2008-2018 average by more than one standard deviation.
• Since 2000, the extent of the non-snow-covered areas of Greenland has increased by 500 km² per year.

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climate-debate

Greenland Temperature Data For 2018

by P. Homewood, April 24, 2019 in NotaLotOfPeopleKnowThat

The DMI has just published its Greenland Climate Data Collection for last year, and it is worth looking at the temperature data:

There are six stations with long records, Upernavik, Nuuk, Ilulissat, Qaqortoq, Narsarsuaq and Tasilaq.

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Throughout Greenland we find that temperatures in the last two decades are little different to the 1920s to 60s.

The only exceptions were 2010 on the west coast sites, which was an unusually warm year, and 2016 on the east coast at Tasilaq, another warm year there.

Noticeably, last year was actually colder than the 1981-2010 average at all of the west and south coast stations.

 

climate-debate

Inconvenient: NASA says a Greenland glacier did an about-face – growing again

by Anthony Watts, March 25, 2019 in WUWT

“…scientists were so shocked to find the change.”

From NASA JPL: Cold Water Currently Slowing Fastest Thinning Greenland Glacier

NASA research shows that Jakobshavn Glacier, which has been Greenland’s fastest-flowing and fastest-thinning glacier for the last 20 years, has made an unexpected about-face. Jakobshavn is now flowing more slowly, thickening, and advancing toward the ocean instead of retreating farther inland. The glacier is still adding to global sea level rise – it continues to lose more ice to the ocean than it gains from snow accumulation – but at a slower rate.

The researchers conclude that the slowdown of this glacier, known in the Greenlandic language as Sermeq Kujalleq, occurred because an ocean current that brings water to the glacier’s ocean face grew much cooler in 2016. Water temperatures in the vicinity of the glacier are now colder than they have been since the mid-1980s.

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See also here in NBS

climate-debate

GREENLAND ICE SHEET SIXTH HIGHEST ON RECORD

by GWPF, December 7, 2019

In 2018, Greenland’s total  surface mass budget (SMB) is almost 150bn tonnes above the average for 1981-2010, ranking as sixth highest on record.

 

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The Danish Meteorological Institute (DMI) also performs daily simulations of how much ice or water the Ice Sheet loses or accumulates. Based on these simulations, an overall assessment of how the surface mass balance develops across the entire Ice Sheet is obtained (Fig. 4).

At the end of the 2018 season (31 August 2018), the net surface mass balance was 517 Gt, which means that 517 Gt more snow fell than the quantity of snow and ice that melted and ran out into the sea.

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climate-debate

Greenland’s Glaciers Expanding Again

by P. Homewood, March 11, 2019 in NotaLotofPeopleKnowThat

As I reported last  September, Greenland’s ice sheet mass balance had grown at close to record levels for the second year running.

To clarify again, the mass balance calculation accounts for:

1) Snowfall

2) Ice melt

3) Ablation

 

In other words, it does not include calving.

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http://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/#

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better to know...?, climate-debate

Polar bear habitat update: abundant sea ice across the Arctic, even in the Barents Sea

by Polar Bear Science, March 12, 2019

Abundant ice in Svalbard, East Greenland and the Labrador Sea is excellent news for the spring feeding season ahead because this is when bears truly need the presence of ice for hunting and mating. As far as I can tell, sea ice has not reached Bear Island, Norway at this time of year since 2010 but this year ice moved down to the island on 3 March and has been there ever since. This may mean we’ll be getting reports of polar bear sightings from the meteorological station there, so stay tuned.


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climate and geology, climate-debate

Novel hypothesis goes underground to predict future of Greenland ice sheet

by Penn State, February 2,  2019 in ScienceDaily

Paleoclimatic records indicate that most of Greenland was ice-free within the last 1.1 million years even though temperatures then were not much warmer than conditions today. To explain this, the researchers point to there being more heat beneath the ice sheet in the past than today.

Data show that when the Iceland hot spot — the heat source that feeds volcanoes on Iceland — passed under north-central Greenland 80 to 35 million years ago, it left molten rock deep underground but did not break through the upper mantle and crust to form volcanoes as it had in the west and east. The Earth’s climate then was too warm for Greenland to have an ice sheet, but once it cooled the ice sheet formed, growing and shrinking successive with ice ages.

climate-debate

Greenland Is Way Cool

by Willis Eschenbach, January 8, 2019

As a result of a tweet by Steve McIntyre, I was made aware of an interesting dataset. This is a look by Vinther et al. at the last ~12,000 years of temperatures on the Greenland ice cap. The dataset is available here.

Figure 1 shows the full length of the data, along with the change in summer insolation at 75°N, the general location of the ice cores used to create the temperature dataset.

Figure 1. Temperature anomalies of the Greenland ice sheet (left scale, yellow/black line), and the summer insolation in watts per square metre at 75°N (right scale, blue/black line). The red horizontal dashed line shows the average ice sheet temperature 1960-1980.

I’ll only say a few things about each of the graphs in this post. Regarding Figure 1, the insolation swing shown above is about fifty watts per square metre. Over the period in question, the temperature dropped about two and a half degrees from the peak in about 5800 BCE. That would mean the change is on the order of 0.05°C for each watt per square metre change in insolation …

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biology+acidification

Algae thrive under Greenland sea ice

by Bigelow Laboratory for Ocean Sciences, January 8, 2019 in ScicneDaily

Microscopic marine plants flourish beneath the ice that covers the Greenland Sea, according to a new study. These phytoplankton create the energy that fuels ocean ecosystems, and the study found that half of this energy is produced under the sea ice in late winter and early spring, and the other half at the edge of the ice in spring.

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climate-debate

“Terrifying Sea-Level Prediction Now Looks Far Less Likely”… But “marine ice-cliff instability” is “just common sense”

by David Middleton, January 5, 2019 in WUWT

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Marine ice cliff instability (MICI) “has not been observed, not at such a scale,” “might simply be a product of running a computer model of ice physics at a too-low resolution,” ignores post glacial rebound, couldn’t occur before ” until 2250 or 2300″… Yet “the idea is cinematic,” “it’s just common sense that Antarctic glaciers will develop problematic ice cliffs” and something we should plan for…

“Our results support growing evidence that calving glaciers are particularly sensitive to climate change.”  Greenland’s climate is always changing… Always has and always will change… And the climate changes observed over the last few decades are not unprecedented. The Greenland ice sheet is no more disappearing this year than it was last year and it is physically impossible for the ice sheet to “collapse” into the ocean.

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Figure 6. Jakobshavn Isbrae. (Wikipedia and Google Earth)

climate-debate

GREENLAND ICE SHEET SIXTH HIGHEST ON RECORD

by GWPF, December 7, 2018

The Danish Meteorological Institute (DMI) also performs daily simulations of how much ice or water the Ice Sheet loses or accumulates. Based on these simulations, an overall assessment of how the surface mass balance develops across the entire Ice Sheet is obtained (Fig. 4).

At the end of the 2018 season (31 August 2018), the net surface mass balance was 517 Gt, which means that 517 Gt more snow fell than the quantity of snow and ice that melted and ran out into the sea. This number only contains the balance at the surface, and thus not the total balance, which also includes melting of glaciers and calving of icebergs.

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Although the total SMB  (Surface Mass Budget) for the 2016-2017 and 2017-2018 seasons are similar, development during the two seasons has been very different. Last year, the season began by gaining a lot of mass during the winter, whilst the development in SMB from the summer onwards reflected the long-term average. During the 2017-2018 season, SMB remained in line with the average from 1981-2010 until the summer, after which the development in SMB was higher than average.

climate-debate

How the Greenland ice sheet fared in 2018

by R. Mottram et al.  (DMI), October 27, 2018 in ScienceNordic

The end of August traditionally marks the end of the melt season for the Greenland ice sheet as it shifts from mostly melting to mostly gaining snow.

As usual, this is the time when the scientists at DMI and our partners in the Polar Portal assess the state of the ice sheet after a year of snowfall and ice melt. Using daily output from a weather forecasting model combined with a model that calculates melt of snow and ice, we calculate the “surface mass budget” (SMB) of the ice sheet.

This budget takes into account the balance between snow that is added to the ice sheet and melting snow and glacier ice that runs off into the ocean. The ice sheet also loses ice by the breaking off, or “calving”, of icebergs from its edge, but that is not included in this type of budget. As a result, the SMB will always be positive – that is, the ice sheet gains more snow than the ice it loses.

For this year, we calculated a total SMB of 517bn tonnes, which is almost 150bn tonnes above the average for 1981-2010, ranking just behind the 2016-17 season as sixth highest on record.

By contrast, the lowest SMB in the record was 2011-2012 with just 38bn tonnes, which shows how variable SMB can be from one year to another.

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Maps show the difference between the annual SMB in 2017 (left) and 2018 (right) compared with the 1981-2010 period (in mm of ice melt). Blue shows more ice gain than average and red shows more ice loss than average. (Credit: DMI Polar Portal)

climate-debate

Greenland Temperatures In 2017

by P. Homewood, July 1, 2018 in NotaLotofPeopleKnowThat

As we all know, Greenland is warming up rapidly, causing the ice sheet to melt faster and faster.

Well, according to the BBC and New York Times, at least.

Only one slight problem – the temperature record shows quite a different story.

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There is certainly no evidence of rising temperature trends, and every likelihood that temperatures will plummet again when the AMO turns cold again.

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biology+acidification, climate-debate

Glacier depth affects plankton blooms off Greenland

by Helmholtz Centre for Ocean Research Kiel (GEOMAR), Auhsut 14, 2018 in ScienceDaily

The unusual timing of highly-productive summer plankton blooms off Greenland indicates a connection between increasing amounts of meltwater and nutrients in these coastal waters. Researchers now show that this connection exists, but is much more complex than widely supposed. Whether increasing meltwater has a positive or negative effect on summertime phytoplankton depends on the depth at which a glacier sits in the ocean.

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“So, the study shows that further melting of Greenland’s glaciers only leads to stronger summer plankton blooms under very specific conditions, an effect that will ultimately end with very extensive further melting,” Hopwood summarizes the results of the study.

climate-debate

New Science Affirms Arctic Region Was 6°C Warmer Than Now 9000 Years Ago, When CO2 Levels Were ‘Safe’

by K. Richard, July 12, 2018 in NoTricksZone

Unearthed new evidence (Mangerud and Svendsen, 2018) reveals that during the Early Holocene, when CO2 concentrations hovered around 260 ppm, “warmth-demanding species” were living in locations 1,000 km farther north of where they exist today in Arctic Svalbard, indicating that summer temperatures must have been about “6°C warmer than at present”.

Proxy evidence from two other new papers suggests Svalbard’s Hinlopen Strait  may have reached about 5 – 9°C warmer than 1955-2012 during the Early Holocene (Bartels et al., 2018), and Greenland may have been “4.0 to 7.0 °C warmer than modern [1952-2014]” between 10,000 and 8,000 years ago according to evidence found in rock formations at the bottom of ancient lakes (McFarlin et al., 2018).

In these 3 new papers, none of the scientists connect the “pronounced” and “exceptional” Early Holocene warmth to CO2 concentrations.

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