New Grid Standards Set To Prevent A Texas Freeze Repeat

By Charles Kennedy - Sep 24, 2021, 

The Federal Energy Regulatory Commission and the North American Electric Reliability Corp have devised and issued a set of new grid reliability standards to avoid a repeat of the Texas Freeze that left millions without power and heating amid a cold spell and saddled thousands with massive electricity bills.

"I cannot, and will not allow this to become yet another report that serves no purpose other than to gather dust on the shelf," said Rich Glick, chairman of the FERC, as quoted by Reuters.

Among the new requirements is one that should see utilities identify and take steps to protect cold-weather critical components of the grid, build new units, or retrofit existing ones to be able to withstand extreme weather, and prepare plans for handling freeze-related outages.

The Texas Freeze, which was the result of a Polar vortex that froze swathes of the U.S. but hit the Lone Star State the hardest, caused power outages because power plants simply froze as their operators had not weatherized them. It also caused a shortage of electricity because many gas wells that supply the commodity to the plants also froze. The cold spell resulted in the biggest drop in U.S. oil production, too, at 40 percent of the nation's total.

As a result of all these outages and shortages, at one point as many as 2 million Texans were without power, gas prices hit record highs on the wholesale market, and ERCOT resorted to rolling blackouts.

The new standards by the FERC and NERC are supposed to help prevent this from happening again. FERC does not have jurisdiction over ERCOT—the Texas grid operator—but NERC does have jurisdiction when it comes to reliability matters.

Texas is working to prevent another Freeze, too, which many blamed on the fact that the Texas grid is isolated from the national grid, which made it extra vulnerable to the effects of extreme weather.

By Charles Kennedy for Oilprice.com

 

U.S. Arrests Senior Russian LNG Executive For Tax Fraud

By Irina Slav - Sep 24, 2021

The U.S. Department of Justice has arrested the chief financial officer of Novatek, Russia’s largest private gas company and biggest LNG exporter, on charges of tax fraud.

In a statement, the DoJ said that Mark Gyetvay had engaged in a scheme to defraud the United States by hiding his ownership of sizeable offshore assets—a sum of about $93 million—and had also failed to file tax returns and pay taxes “on millions of dollars of income.”

According to the DoJ, Gyetvay engaged in the concealment practice after he became the chief financial officer of Novatek, upon which he was allegedly presented with “lucrative stock options and/or stock-based compensation”.

Gyetvay then proceeded to set up two Swiss bank accounts, according to the DoJ allegations, where he put these assets and then removed himself as the owner of the accounts by transferring ownership to his then-wife, who was a Russian citizen.

In addition to this asset concealment, Gyetvay also “allegedly did not timely file his U.S. tax returns, nor did he file all of the required Reports of Foreign Bank and Financial Accounts (FBARs) forms certain U.S. taxpayers are required to file annually that disclose their control over assets maintained in foreign bank accounts.”

On top of that, according to the allegations, some of the taxes that Gyetvay did file were false. He also allegedly submitted a false offshore compliance form with the U.S. tax authorities, saying that his former failure to submit the forms relevant to holdings in foreign banks had not been wilful.

According to a report in the Financial Times, Mark Gyetvay, who helped expand Novatek into the LNG export major it is today, is one of the most popular business executives in Russia and internationally in the oil and gas industry. If found guilty, he faces decades in prison.

By Irina Slav for Oilprice.com

 

JPM, Barclays, And Citigroup Are Betting Big On Arctic Oil

By City A.M - Sep 23, 2021, 

Oil and gas companies are set to ramp up production in the Arctic by 20 per cent in the next five years, according to a new report shared with City A.M. this morning.

The main Arctic expansionists – Gazprom, Total and ConocoPhillips – are backed by hundreds of billions of pounds from dozens of City banks and investors, despite many holding commitments to restrict fossil financing in the region, Paris-based think tank Reclaim Finance claimed this morning.

The report details £230 billion of loans and underwriting from commercial banks to Arctic oil and gas expansionists between 2016 and 2020, including numerous key players from the City.

JPMorgan Chase was the biggest investor with $18.6 billion, followed by Barclays ($13.2 billion), Citigroup ($12.2  billion) and BNP Paribas ($11.8 billion).

Investors are further holding around $272 billion in Arctic fossil developers as of March of this year, with BlackRock ($28.5 billion), Vanguard ($21.6 billion) and Amundi ($12.9 billion) leading the pack, all without Arctic exclusion policies.

Restriction policies

Despite numerous commitments from financial institutions not to support oil and gas extraction in the Arctic, the report found that 20 of the 30 banks that are fuelling expansion in the Arctic region have so-called Arctic restriction policies, not a single one excludes support to companies developing new oil and gas projects in the region.

Notably, HSBC and BNP Paribas were the top financiers of Arctic expansionists in 2020, despite adopting Arctic exclusion policies early on compared to their peers.

Moreover, financial institutions such as AXA and Morgan Stanley have adopted highly limited definitions of the Arctic which permit ongoing expansion, while Goldman Sachs and Crédit Agricole are among several financial players restricting financing only to oil projects, thereby permitting fossil gas.

Meanwhile, amongst insurers, essential players for Arctic oil and gas extraction, 13 out of the world’s top

46 companies have an Arctic sector underwriting policy.

Climate breakdown

The findings come just weeks after the International Panel on Climate Change warned of accelerating climate breakdown in the Arctic, with temperatures rising twice as quickly as elsewhere, while NASA s set to release its annual survey of Arctic sea ice loss in the coming days.

Commenting on the findings, the report’s author, Paris-based Alix Mazounie, told City A.M. this morning: “The Arctic is a climate bomb, and our research shows that the oil and gas industry is hellbent on setting it off, thus blowing up our chances of avoiding runaway climate breakdown.”

This interactive map allows you to select a bank, investor or insurer and to navigate through the oil and gas companies involved in the Arctic.

By City AM

 

Microbial 'theft' enables breakdown of methane, toxic methylmercury

by Oak Ridge National Laboratory

Researchers gained new insights into the mechanisms some methane-feeding bacteria called methanotrophs use to break down the toxin methylmercury. Credit: Andy Sproles/ORNL, U.S. Dept. of Energy; Jeremy Semrau/Univ. of M

A team led by the Department of Energy's Oak Ridge National Laboratory and the University of Michigan have discovered that certain bacteria can steal an essential compound from other microbes to break down methane and toxic methylmercury in the environment.

The findings could inform strategies that aim to manipulate these microorganisms to reduce emissions of methane, a powerful greenhouse gas, and detoxify methylmercury, a potent neurotoxin that can accumulate in the food supply.

The study, published in The ISME Journal, found that certain classes of methanotrophs or  methane-consuming bacteria that were previously thought unable to degrade methylmercury can actually break it down in the environment. This activity is possible because the microbes are equipped with the cellular machinery to absorb and use a compound called methanobactin that is produced by other microbes.

Methanotrophs are widespread in nature. They live near methane and air interfaces, such as the topmost layer of soils, river sediments and wetlands where they can access oxygen while feeding on the methane that flows up from the anoxic, or oxygen-deficient, environments below.

These bacteria play a critical role in the carbon cycle, consuming substantial amounts of methane generated by other microbes called methanogens. This natural counterbalance is important in limiting methane emissions, which are 25 times more potent than carbon dioxide at warming Earth's atmosphere.  

Understanding more about the way the methane-feeders function may point to methods to use them like levers to control methane emissions. The new knowledge can also better inform climate models that predict the planet's future.

Researchers discovered these new methanotroph behaviors while studying another global problem: mercury pollution. ORNL has a long history of breakthroughs related to mercury, including their 2013 discovery of the genes that enable microbes to transform mercury into the toxin methylmercury.

In 2017, an ORNL-led team was the first to demonstrate that some methanotrophs can break down methylmercury, a process called demethylation. Their newest findings build on that discovery, showing that more methanotrophs than previously known can degrade methylmercury.

"As we gain new insights about methanotrophic activities, we may be able to more effectively manipulate these microbial communities to reduce methane emissions and enhance mercury detoxification in the environment," said Baohua Gu, an ORNL corporate fellow and biogeochemist.

Producers and cheaters

Methanotrophs are looking for the easiest, quickest food supply, with a target of single-carbon compounds like methane and methylmercury, which have similar chemical structures. These microbes also require copper to fuel their metabolic processes. It is this need for copper that can limit methanotrophic activity, driving the microbes to seek copper sources in the environment using many different methods.

Some methanotrophs use a surface protein to secure copper. Others secrete a compound called methanobactin, or MB, that binds with copper in the environment and facilitates copper acquisition. Previous findings by the team had shown that only bacteria with the genetic and metabolic machinery to produce MB can break down methylmercury.

The researchers' latest findings demonstrate that some methanotrophs that do not make MB can detoxify methylmercury by using MB secreted by other methanotrophs. In other words, they steal it.

"They are effectively what we call cheaters," said University of Michigan microbiologist Jeremy Semrau. "This has been observed before, where one microorganism produces something that is of benefit to the general community and others steal it. This enables some methanotrophs to meet their copper requirements."

The research team also showed that successful theft of MB requires that methanotrophs have the gene, named mbnT, that enables production of a specific protein called the TonB transporter. Aptly named, this protein moves MB—and the associated copper—into the microbe, enabling the breakdown of methylmercury and methane.

Scientists at U-M engineered a strain of methanotrophs without the mbnT gene, and the team at ORNL analyzed the mercury in the samples. The removal of the mbnT gene and transporter protein in these microbes effectively disabled their ability to take up MB or detoxify methylmercury.

These insights could inform future paths toward addressing mercury pollution in the environment.

"I think it's a wonderful strategy going forward where we might be able to utilize methanotrophs to help remediate mercury contaminated sites, and that this might actually be going on, to some extent, naturally," Semrau said.

Another piece of the puzzle

Methanotrophs are common in the environment, but there is still a lot to learn about their activities. A team led by ORNL environmental scientist Scott Brooks collaborated with Semrau's group at U-M on the discovery of several novel methanotrophs in East Fork Poplar Creek, a mercury-contaminated stream flowing through the Oak Ridge Reservation that has been studied for decades.

Brooks and his team have been studying biofilms, which are complex communities of algae and bacteria that accumulate on creek rocks as "green slime." Though biofilms are only about as thick as a few stacked credit cards, they are hot spots for mercury and nutrient processing.

The ORNL team had previously found that oxygen-deficient pockets within these biofilms house microbes that are transforming mercury into its most toxic form: methylmercury. Their recent discovery of methanotrophs in the oxygen-rich recesses of these same biofilms means that methylmercury breakdown is also occurring naturally in the creek.

"There are some really steep chemical gradients and changes in concentration taking place over a very small distance," Brooks said. That includes dissolved oxygen that "disappears within a few tenths of a millimeter."

Those tiny pockets of oxygen are enough for methanotrophs to thrive. Preliminary analysis showed that microbial activity producing methylmercury outpaced the methanotrophic activity breaking down the toxin. With further study, scientists could potentially identify methods of tipping the balance toward methylmercury degradation.

"This is a nice marriage of two different research projects working in parallel," Brooks said. "We're seeing things that are consistent with one another and that helps us confirm what is happening with mercury cycling in these complex microbial communities."Newly identified microbial process could reduce toxic methylmercury levels

More information: Christina S. Kang-Yun et al, Evidence for methanobactin "Theft" and novel chalkophore production in methanotrophs: impact on methanotrophic-mediated methylmercury degradation, The ISME Journal (2021). DOI: 10.1038/s41396-021-01062-1

Journal information: ISME Journal 

Provided by Oak Ridge National Laboratory 

 

E. Africa crude pipeline math does not add up

TUESDAY SEPTEMBER 28 2021

In the past two years, Africa has experienced some damning climate change events that have affected millions of people.

The climatic events, including unforgiving droughts and floods, have resulted in the destruction of property, food insecurity and even loss of lives.

Ugandan Minister of Water and Environment, Sam Cheptoris, recently confirmed the same, saying: “Uganda is already feeling the impacts of climate change. From extreme drought to extreme flooding, the threat is growing in Africa.

For governments, regional stakeholders and civil society to collaborate on our common challenge, we need to act now and act together. Climate action is a path to a better future for Africa and for the world.”

And yet, as climate change hits us hard and costs us lives and livelihoods, the Ugandan Cabinet moved in haste to approve a special Bill to pave the way for the construction of the East African Crude Oil Pipeline (EACOP)

The climate change consequences of carrying on with the project are clear. That the project will emit up to 34 million tonnes of carbon annually has not yet been disputed by anyone, including TotalEnergies, China National Offshore Oil Corporation (CNOOC), and the governments of Uganda and Tanzania.

Backers of the pipeline and associated projects have sought to justify the project from an economics standpoint.

The governments of Tanzania and Uganda are expecting economic benefits from the oil extractions and the EACOP projects. But unfortunately, even the economics do not hold up to scrutiny.

Since the discovery of oil in Uganda, the government has continually put its economy at risk by fully immersing itself in the EACOP projects. This has resulted in overborrowing.

While among the reasons cited for the overborrowing is the expectation of oil revenue, the ones benefiting from this exercise are the oil companies that enjoy tax breaks and seek additional concessions through laws such as the EACOP Bill.

There are also many uncertainties and risks in the oil sector. The plummeting oil prices, strides made globally on clean energy transition and the increasing threats from international litigation should concern Uganda as its economic future is put at risk.

While our eyes glow when the oil barons preach the gospel of the revenue from oil, it is clear that the golden age of oil is on its deathbed.

In fact, experts from the UK-based think tank Climate Policy Initiative (CPI) say that Uganda’s oil reserves have already lost over 70 percent of their value since 2013.

In 2020 Tullow, who was the then proponent of EACOP and associated projects, appeared to step back and cut its losses.

Tullow was expecting to fetch $900 million, but the sale ended up at $575 million. The Ugandan government had to settle for taxes to the tune of $14 million instead of the $167 million it was demanding.

Increasingly, more banks and financial institutions have been avoiding investments in fossil fuels like the plague. Globally, over 100 financial institutions have announced their intention to divest or are divesting from fossil fuels.

In the case of the pipeline, 11 out of the 25 banks approached to finance the project have have expressed their reservations due to the project’s cost on people living within the corridor and climate change concerns.

It is apparent that they have done their calculations and realised that this pipeline will not offer good returns on their investments and would therefore culminate in stranded assets.

Perhaps even worse, is that the Ugandan government could also extend the existing 10-year tax holiday granted to the EACOP developers. Experts estimate that this will result in a 10 percent decrease in earnings expected by the Ugandan government from the Ugandan oil.

In comparison, tourism contributes up to 10 percent of the Ugandan GDP and is responsible for 23 percent of Uganda’s exports.

The sector has earned the country about $1.6 billion. It is, therefore, not complicated. The oil activities in Uganda’s national parks, forests, lakes, rivers and other natural resources will negatively affect this promising sector.

Additionally, this pipeline and associated projects will significantly affect the agriculture sector. Seven people out of 10 in the labour force in Uganda are employed in agriculture.

This poses a huge risk following the land acquisition of up to 5,300 hectares that 15,000 households depend on for their livelihoods. The same concerns go for the fishing industry, which employs over 1.2 million people.

If we are keen on development, we need to focus our energies on green opportunities like tourism, agriculture, fishing, and renewable energy that are already injecting fortunes into our economies and whose potential we are yet to fully exploit.

Let us embrace a people-centred model, geared towards a sustainable, green future and not one rigged to benefit big oil companies like Total Energies and CNOOC.

Nakate is the founder of the RiseUp Movement. Elmawi is a lawyer and the Coordinator of the #StopEACOP Campaign

Maximise benefits of Kenya’s carbon pricing mechanism

MONDAY SEPTEMBER 27 2021 

Treasury Cabinet Secretary Ukur Yatani recently announced the government’s intention to introduce carbon emissions pricing mechanisms to combat climate change and support sustainable development. This move is welcome and timely.

Carbon pricing mechanisms such as Emissions Trading Systems (ETS), carbon taxes, or a hybrid of the two, have been demonstrated to be efficient policy tools in over 46 countries in driving down emissions that are responsible for climate change, and delivering other vital national priorities.

They achieve this by imposing caps on emissions, and applying charges on firms that exceed them, or requiring them to purchase additional emission allowances from the market. This system provides economic incentives for polluters to cut emissions to avoid incurring costs.

To maximise benefits to the country, the envisaged system should direct a portion of carbon pricing revenues to the conservation, restoration, and sustainable management of forests, agricultural land, and other natural ecosystems.

Doing so would deliver significant and cost-effective natural solutions to tackling climate change, while simultaneously helping to achieve Kenya’s other core goals of enhancing livelihoods and economic growth and conserving its rich biodiversity.

The land and forestry sectors in Kenya, including agriculture, generate the highest share (38 percent) of carbon emissions due to deforestation and land degradation.

They also hold the biggest emissions reductions potential that could get the country almost 90 percent of the way to meeting its Paris Agreement target.

However, these crucial sectors are receiving disproportionately less climate finance, thus impeding effective climate action. A good carbon pricing architecture could help rectify this glaring anomaly.

Carbon pricing is one of the tools that can help Kenya realise its commitment under the Paris Agreement of cutting emissions by 32 percent by 2030 and strengthening the country’s resilience to worsening climate shocks.

It can aid in raising part of the Sh6.8 trillion (US$62 billion) needed to implement Kenya’s updated national climate change plan or Nationally Determined Contribution (NDC), that is largely (87 percent) dependent on external funding.

Under an Emissions Trading model of carbon pricing, a part of the charges imposed on companies exceeding their emissions limits could be invested in natural ecosystems that are critical in addressing climate change.

These firms could also be allowed to purchase carbon offsets that conserve nature, instead of paying penalties, but this arrangement should be strictly managed to maintain the integrity of the emissions cap.

The government could also institute emission caps on the land sector to incentivise emissions cuts, though this may be a challenging proposition politically.

In a carbon tax scenario, a share of tax revenues could be invested into protecting and restoring natural ecosystems as a solution to climate change, or the government can permit companies to purchase carbon offsets that are linked to conserving those ecosystems.

These two suggestions are consistent with options being considered under the draft National Green Fiscal Incentives Framework Policy.

To ensure that carbon pricing mechanisms deliver optimal benefits, existing and upcoming voluntary carbon offset projects in Kenya need to be ‘nested’ or integrated into the national system to reduce emissions from deforestation and forest degradation (REDD+).

This ‘nesting’ will enhance private and public financial flows to projects that are keeping vital carbon-rich ecosystems intact, while ensuring equitable distribution of compensation for those delivering emissions reductions, right from the grassroots to national levels.

Kenya is making headway in this regard through the establishment of the National Expert group (NEG) on REDD+ nesting and related activities, thereby signalling to the world its intention to generate a welcoming and enabling environment for continued investment.

Carbon pricing mechanisms have been successfully implemented in developed and developing countries. For instance, Costa Rica’s tax on fossil fuels generates Sh3.3 billion (US$30 million) yearly for forest conservation and restoration, while lowering carbon emissions from fuel use.

FOREST CREDITS

In Colombia, companies subject to the carbon tax may reduce their tax obligations by purchasing carbon offsets that protect nature.

The tax can also be paid with carbon credits from energy efficiency or other energy related projects. Additionally, a portion of the collected tax revenues is invested in nature conservation.

The US State of California’s Emissions Trading System allows use of nature-based offsets to fulfil a small portion of emission reduction requirements, including through forest carbon offsets.

To date, nearly 165 million forest credits have been traded under the system, and approximately $432 million of the revenue from forest credits has gone to Native American communities.

As discussions proceed on the design of Kenya’s carbon pricing mechanism, there is a significant opportunity to ensure it delivers the most benefits to the country, including climate action, biodiversity conservation, and socioeconomic development.

Bank of America: Carbon offset market may need to grow fiftyfold to meet 2050 net-zero emissions goals

Catherine Clifford@IN/CATCLIFFORD

PUBLISHED MON, SEP 27 2021

KEY POINTS

The carbon offset market may need to grow by as much as 50 times if companies are going to meet 2050 net-zero greenhouse gas emissions goals, a research note from Bank of America said.

Offsets issued in 2020 were equivalent to 210 million metric tons of carbon dioxide emissions, which is 0.4% of total global emissions, the note said.

Achieving net-zero energy emissions by 2050 will demand approximately 7.6 gigatons of carbon dioxide offsets or removal, it said.


Smoke rises from a coal-fired power plant in Obilic, near Pristina, Kosovo, November 18, 2019.
Ognen Teofilovski | Reuters

The carbon offset market may need to grow by as much as 50 times if companies are going to meet 2050 net-zero greenhouse gas emissions goals, according to a new research note from Bank of America Global Research.

Net-zero, also known as carbon neutrality, is achieved when an entity removes as much carbon dioxide and other greenhouse gases from the atmosphere as it releases into it, according to the World Resources Institute, a nonprofit global research organization. Removal methods include restoring forests — because trees remove carbon dioxide from the air during photosynthesis — or more technical means, such as direct carbon capture technology.

The market for carbon offsets is “still relatively small,” Bank of America said in its research note, which was released to clients Friday and more broadly Monday. Offsets issued in 2020 were equivalent to 210 million metric tons of carbon dioxide emissions either removed or avoided, which is equivalent to 0.4% of total global emissions, BofA said.

Governments around the world have set goals of becoming net zero between 2050 and 2060.

Achieving net-zero emissions by 2050 will demand approximately 7.6 gigatons of carbon dioxide offsets or removal, BofA said. That would be as much as a fiftyfold increase in the offset market, it said. The low end of the growth in demand for carbon offsets would be at least quadrupling, the bank said.

Nations are not likely to meet their 2050 goals, BofA said. “Current policies remain insufficient to adequately incentivize the changes necessary to reach these lofty goals, whether through carbon pricing or other means.”

Many companies are voluntarily setting their own emissions targets, and those stated goals will increase demand for carbon offsets, the note said.

Carbon offsets cost between $2 and $20 per metric ton of emissions removed, admittedly a broad range, and “offer a relatively cheap way to decarbonize,” BofA said.

There are four primary registries for carbon offsets: Verified Carbon Standard, or Verra; The Gold Standard, the American Carbon Registry and the Climate Action Reserve. The market started about 25 years ago with the American Carbon Registry, then called the Environmental Resources Trust, the BofA note said.

Early in the carbon offset markets, projects included chemical processing and industrial and manufacturing projects. Now forestry, land use and renewable energy projects are about 80% of carbon offset projects, the note said. This “may be due to growing interest in nature based solutions,” it said, and to falling prices of renewable energy, such as wind and solar

Scientific team uncovers additional threat to Antarctica's floating ice shelves

by University of California, Irvine

Ice melange, a combination of ice shelf fragments, windblown snow and frozen seawater,

 can act as a glue to fuse large rifts in floating ice in Antarctica. Researchers at UCI and

 NASA JPL found that a thinning of the substance over time can cause rifts to open, 

leading to the calving of large icebergs. Credit: Beck / NASA Operation IceBridge

Glaciologists at the University of California, Irvine and NASA's Jet Propulsion Laboratory have examined the dynamics underlying the calving of the Delaware-sized iceberg A68 from Antarctica's Larsen C ice shelf in July 2017, finding the likely cause to be a thinning of ice melange, a slushy concoction of windblown snow, iceberg debris and frozen seawater that normally works to heal rifts.

In a paper published today in Proceedings of the National Academy of Sciences, the researchers report that their modeling studies showed melange thinning to be a major driver of ice shelf collapse. The circulation of ocean water beneath ice shelves and radiative warming from above, they say, gradually deteriorate ice melange over the course of decades.

As ice shelves are thought to buttress and prevent land-borne glaciers from more rapidly flowing into the ocean, this new knowledge about rift dynamics illuminates a previously underappreciated link between climate change and ice shelf stability.

"The thinning of the ice melange that glues together large segments of floating ice shelves is another way climate change can cause rapid retreat of Antarctica's ice shelves," said co-author Eric Rignot, UCI professor of Earth system science. "With this in mind, we may need to rethink our estimates about the timing and extent of sea level rise from polar ice loss—i.e., it could come sooner and with a bigger bang than expected."

Using NASA's Ice-sheet and Sea-level System Model, observations from the agency's Operation IceBridge mission, and data from NASA and European satellites, the researchers assessed hundreds of rifts in the Larsen C ice shelf to determine which ones were most vulnerable to breaking. They selected 11 top-to-bottom cracks for in-depth study, modeling to see which of three scenarios rendered them most likely to break: If the ice shelf thinned because of melting, if the ice melange grew thinner, or if both the ice shelf and the melange thinned.

"A lot of people thought intuitively, "If you thin the ice shelf, you're going to make it much more fragile, and it's going to break,'" said lead author Eric Larour, NASA JPL research scientist and group supervisor.

Instead, the model showed that a thinning ice shelf without any changes to the melange worked to heal the rifts, with average annual widening rates dropping from 79 to 22 meters (259 to 72 feet). Thinning both the ice shelf and the melange also slowed rift widening but to a lesser extent. But when modeling only melange thinning, the scientists found a widening of rifts from an average annual rate of 76 to 112 meters (249 to 367 feet).

The difference, Larour explained, reflects the different natures of the substances.

"The melange is thinner than ice to begin with," he said. "When the melange is only 10 or 15 meters thick, it's akin to water, and the ice shelf rifts are released and start to crack."

Even in winter, warmer ocean water can reach the melange from below because rifts extend through the entire depth of an ice shelf.

"The prevailing theory behind the increase in large iceberg calving events in the Antarctic Peninsula has been hydrofracturing, in which melt pools on the surface allow water to seep down through cracks in the ice shelf, which expand when the water freezes again," said Rignot, who is also a NASA JPL senior research scientist. "But that theory fails to explain how iceberg A68 could break from the Larsen C ice shelf in the dead of the Antarctic winter when no melt pools were present."

He said that he and others in the cryosphere studies community have witnessed ice shelf collapse on the Antarctic Peninsula, stemming from a retreat that began decades ago.

"We have finally begun to seek an explanation as to why these ice shelves started retreating and coming into these configurations that became unstable decades before hydrofracturing could act on them," Rignot said. "While the thinning ice melange is not the only process that could explain it, it's sufficient to account for the deterioration that we've observed."

Joining Rignot and Larour on this NASA-funded project were Bernd Scheuchl, UCI associate project scientist in Earth system science, and Mattia Poinelli, a Ph.D. candidate in geoscience and remote sensing at Delft University of Technology in the NetherlandsSlushy iceberg aggregates control calving timing on Greenland's Jakobshavn Isbræ

More information: Physical processes controlling the rifting of Larsen C Ice Shelf, Antarctica, prior to the calving of iceberg A68, Proceedings of the National Academy of Sciences (2021). DOI: 10.1073/pnas.2105080118 , www.pnas.org/content/118/40/e2105080118

Journal information: Proceedings of the National Academy of Sciences 

Provided by University of California, Irvine