Clays in Antarctica from millions of years ago reveal past climate changes

Members of the TASMANDRAKE research group of the Andalusian Earth Sciences Institute (IACT), which pertains to the University of Granada and CSIC, have published a research paper in the prestigious international journal Scientific Reports describing their analysis of clays from Antarctica dating back 35.5 million years, to reconstruct past climate changes.

Glaucony grains observed under an electron microscope
[Credit: University of Granada]

Their study was conducted in the area known as Drake Passage—the body of water that separates South America from Antarctica, between Cape Horn (Chile) and the South Shetland Islands (Antarctica). The results help to better understand the climatic conditions prior to the formation of the Antarctic Circumpolar Current, thus evaluating possible links between the development of the ice sheet in Antarctica and the changes in the tectonic and paleoceanographic configuration. Such questions constitute key facets of past climate functioning that provide boundary conditions for today's climate models, which predict a general rise in sea levels over the coming centuries.

The article analyses the relevance as a climatic indicator of the mineral commonly known as 'glauconite', which is more properly termed 'the glauconia facies' or 'glauconia'. This is a type of green clay, formed mainly in shallow marine environments (<500 m) with temperatures below 15° C, under very specific oxygenation conditions.

The existence of this clay formation in the Antarctic region has received little scholarly attention to date compared to other geological records on the planet. The characteristic green-coloured mineral has been observed around Antarctica and the Antarctic Ocean in sedimentary sequences of the Terminal Eocene Event—that is, before one of the main climatic transitions in Earth's history. The Eocene–Oligocene climate transition took place approximately 34–33.6 million years ago.

Northwest region of the Antarctic Peninsula (South Shetland Islands)
[Credit: University of Granada]

This scientific contribution describes, for the first time in the Antarctic Ocean, a glauconitisation event (in which glauconia was formed) approximately 35.5 million years ago in the Weddell Sea, northeast of the Antarctic Peninsula between South America and Antarctica.

The formation of glauconia 35.5 million years ago marks the onset of progressive sea level rise in the north Weddell Sea during the Terminal Eocene. The results of this scientific study thus provide new insights regarding changes in paleoceanographic conditions just prior to the Eocene–Oligocene climate transition and the controversial opening and deepening of Drake Passage.

Studying the weather of the past to predict the future

The separation of the Antarctic continent from South America and Oceania allowed bodies of water to transfer freely between the Pacific and Atlantic Oceans. This new circulation of bodies of water resulted in the Circumpolar Current and, with it, the thermal insulation of the Antarctic and the formation of the ice cap on a continental scale.

Map of Antarctica showing the location of the Antarctic Circumpolar Current (ACC), which flows from west to east.
The ACC is a fundamental element in the deep global circulation connecting the Pacific, Atlantic, and Indian
Oceans. It is therefore an important part of the global ocean circulation network that distributes
 heat around the Earth [Credit: University of Granada]

The opening of Drake Passage between South America and the Antarctic Peninsula is therefore considered one of the most important events in the history of the Earth's oceanic and atmospheric circulation. However, in the absence of dating for the formation of the sedimentary basins of Drake Passage, it is difficult to specify the precise age when the Passage began to open up and the Circumpolar Current started to form. The glauconia analysis conducted by the TASMANDRAKE research group contributes to progress in this area of study.

To put these changes into perspective, Adrian Lopez Quiros, the principal author of the research, notes that "it is necessary to study the past to understand the present and help predict the future," by better understanding the tectonic, climatic, and paleoceanographic conditions that led to the onset and subsequent evolution of this important ocean current.

The United Nations' Intergovernmental Panel on Climate Change (IPCC), a major reference source for climate forecasts, established several possible future climate scenarios in 2014. However, the new data, when comparing simulations with real-world data, predict even greater impacts than those previously foreseen in the IPCC climate scenarios. Therefore, climate change is developing faster than previously thought. With its research, the TASMANDRAKE group aims to provide new variables for these models—focusing on sediments and geophysics—to ensure that its results reflect real-life events even more accurately, especially in terms of the transoceanic currents, global warming, and rising sea levels.

Source: University of Granada [January 23, 2020]

Arctic sea ice can't 'bounce back'

A team of scientists led by the University of Exeter used the shells of quahog clams, which can live for hundreds of years, and climate models to discover how Arctic sea ice has changed over the last 1,000 years.

Quahog clams [Credit: Paul Butler]

They found sea ice coverage shifts over timescales of decades to centuries - so shrinking ice cannot be expected to return rapidly if climate change is slowed or reversed.

The study examined whether past ice changes north of Iceland were "forced" (caused by events such as volcanic eruptions and variations in the sun's output) or "unforced" (part of a natural pattern).

At least a third of past variation was found to be "forced" - showing the climate system is "very sensitive" to such driving factors, according to lead author Dr Paul Halloran, of the University of Exeter.

"There is increasing evidence that many aspects of our changing climate aren't caused by natural variation, but are instead 'forced' by certain events," he said.

"Our study shows the large effect that climate drivers can have on Arctic sea ice, even when those drivers are weak as is the case with volcanic eruptions or solar changes.

"Today, the climate driver isn't weak volcanic or solar changes - it's human activity, and we are now massively forcing the system."

Co-author of the study Professor Ian Hall, from Cardiff University, said: "Our results suggest that climate models are able to correctly reproduce the long-term pattern of sea ice change.

"This gives us increased confidence in what climate models are telling us about current and future sea ice loss."

When there is lots of sea ice, some of this drifts southwards and, by releasing fresh water, can slow the North Atlantic Ocean circulation, otherwise known as the Atlantic Meridional Overturning Circulation (AMOC).

The AMOC brings warm water from the tropics towards the Arctic, so slowing it down cools this region and allows sea ice to grow further.

So, with less ice the AMOC can bring in more warm water - a so-called "positive feedback" where climate change drives further warming and sea ice loss.

Quahog clams are thought to be the longest-living non-colonial animal on Earth, and their shells produce growth rings which can be examined to measure past environmental changes.

Dr Halloran is part of the Global Systems Institute, which brings together experts from a wide range of fields to find solutions to global challenges.

The findings are published in the journal Scientific Reports.

Source: University of Exeter [January 21, 2020]

Preparing land for palm oil causes most climate damage

New research has found preparing land for palm oil plantations and the growth of young plants causes significantly more damage to the environment, emitting double the amount of greenhouse gases than mature plantations.

Peat swamp deforestation and drainage for new oil palm plantations in North Selangor
Peat Swamp Forest, Malaysia [Credit: Stephanie Evers]

This is the first study to examine the three main greenhouse gas emissions across the different age stages of palm oil plantations. It was carried out by plant scientists from the University of Nottingham in the North Selangor peat swamp forest in Malaysia with support from the Salangor State Forestry Department. It has been published in Nature Communications.

Palm oil is the most consumed and widely traded vegetable oil in the world. Global demand has more than tripled in the last eighteen years, from around 20 million tonnes in 2000 to over 70 million in 2018 and Malaysia is the world's second largest producer. The University of Nottingham researchers analysed five sites at four different stages of land use: secondary forest, recently drained but uncleared forest, cleared and recently planted young oil palm plantation and mature oil palm plantation.

Laboratory analysis of soil and gas from these sites showed that the greatest fluxes of CO2 occurred during the drainage and young oil palm stages with 50% more greenhouse gas emissions than the mature oil palms. These emissions also account for almost a quarter of the total greenhouse emissions for the region.

Tropical peat swamp forests hold around 20% of global peatland carbon. However, the contribution of peat swamp forests to carbon storage is currently under threat from large-scale expansion of drainage-based agriculture including oil palm and pulp wood production on peatlands.

Draining peatlands increases the oxygen levels in the soil, which in turn increases the rate of decomposition of organic material, resulting in high CO2 emissions from drained peatlands. In addition to CO2, peatlands also emit the powerful greenhouse gases (CH4 and N2O8)..

Dr Sofie Sjogersten from the University of Nottingham's School of Biosciences led the research and said: "Tropical peat swamps have historically been avoided by palm oil growers due to the amount of preparation and drainage the land needs, but as land becomes more scarce there has been an increased demand to convert sites and the periphery of North Selangor is being heavily encroached upon by palm oil plantations. Our research shows that this conversion comes at a heavy cost to the environment with greater carbon and greenhouse gas emissions being caused by the early stages of the growth of palm oil."

Source: University of Nottingham [January 21, 2020]

Ozone-depleting substances caused half of late 20th-century Arctic warming, says study

A scientific paper published in 1985 was the first to report a burgeoning hole in Earth's stratospheric ozone over Antarctica. Scientists determined the cause to be ozone-depleting substances - long-lived artificial halogen compounds. Although the ozone-destroying effects of these substances are now widely understood, there has been little research into their broader climate impacts.

A new study shows that half of all Arctic warming and corresponding sea-loss during the late 20th century was
caused by ozone-depleting substances. Here, icebergs discharged from Greenland's Jakobshavn Glacier
[Credit: Kevin Krajick/Earth Institute]

A recent study published in Nature Climate Change by researchers at Columbia University examines the greenhouse warming effects of ozone-depleting substances and finds that they caused about a third of all global warming from 1955 to 2005, and half of Arctic warming and sea ice loss during that period. They thus acted as a strong supplement to carbon dioxide, the most pervasive greenhouse gas; their effects have since started to fade, as they are no longer produced and slowly dissolve.

Ozone-depleting substances, or ODS, were developed in the 1920s and '30s and became popularly used as refrigerants, solvents and propellants. They are entirely manmade, and so did not exist in the atmosphere before this time. In the 1980s a hole in Earth's stratospheric ozone layer, which filters much of the harmful ultraviolet radiation from the sun, was discovered over Antarctica. Scientists quickly attributed it to ODS.

The world sprang into action, finalizing a global agreement to phase out ODS. The Montreal Protocol, as it is called, was signed in 1987 and entered into force in 1989. Due to the swift international reaction, atmospheric concentrations of most ODS peaked in the late 20th century and have been declining since. However, for at least 50 years, the climate impacts of ODS were extensive, as the new study reveals.

Scientists at Columbia's School of Engineering and Applied Science and the Lamont-Doherty Earth Observatory used climate models to understand the effects of ODS on Arctic climate. "We showed that ODS have affected the Arctic climate in a substantial way," said Lamont-Doherty researcher Michael Previdi. The scientists reached their conclusion using two very different climate models that are widely employed by the scientific community, both developed at the U.S. National Center for Atmospheric Research.

The results highlight the importance of the Montreal Protocol, which has been signed by nearly 200 countries, say the authors. "Climate mitigation is in action as we speak because these substances are decreasing in the atmosphere, thanks to the Montreal Protocol," said Lorenzo Polvani, lead author of the study and a professor in Columbia's Department of Applied Physics and Applied Mathematics. "In the coming decades, they will contribute less and less to global warming. It's a good-news story."

Source: Columbia University [January 20, 2020]

Pyrenees glaciers 'doomed', experts warn

Glaciers nestled in the lofty crags of the Pyrenees mountains separating France and Spain could disappear within 30 years as temperatures rise, upending ecosystems while putting local economies at risk, scientists say.

A view of the Pyrenees from the observatory at the Pic du Midi de Bigorre, where the average temperature
has risen by 1.7 degrees since 1880 [Credit: Pascal Pavani/AFP]

"We can't set a precise date but the Pyrenees glaciers are doomed," Pierre Rene, a glaciologist with the region's Moraine glacier study association, told AFP.

He estimates the end will come by 2050, based on the group's measurements of nine of the 15 glaciers on the French side over the past 18 years.

The United Nations has said the past decade has been the hottest on record and warned that persistent greenhouse gas emissions were expected to push average global temperatures even higher, leading to retreating ice cover, rising sea levels and increasingly extreme weather. It also confirmed that 2019 was the second hottest year on record, after 2016.

Surveys, core samples and GPS tracking of the Pyrenees glaciers all point to the same conclusions already noted at glaciers in the Alps and elsewhere: Warmer and drier winters appear to be inexorably shrinking and thinning the ice fields.

The total surface area of the nine glaciers tracked by Moraine now stands at 79 hectares (195 acres) compared with 140 hectares just 17 years ago, Rene said.

That is just a small fraction of the 450 hectares they covered in the middle of the 19th century—and the pace of decline is accelerating.

Since 2002, the nine glaciers have lost 3.6 hectares every year, the equivalent of five soccer pitches, Moraine says in its report on the 2019 season.

Last year was no exception, with the bottom edge of five glaciers tracked by Moraine retreating by 8.1 metres (27 feet) on average last summer, up from 7.9 metres recorded in previous years, it said.

'Wiped off the map'

Scientists also warn of the hit to high-altitude ecosystems and biodiversity, with consequences that will ripple well beyond the mountainous zones.

Glaciers and the cold rivers they feed harbour bacteria and fungi that have adapted to the harsh conditions, including the near-absence of light, said Sophie Cauvy-Fraunie, a researcher at the INRAE agricultural and environmental institute.

Microscopic algae also provides a first link in the food chain of glacier environments, sustaining glacial fleas and other insects.

As temperatures rise and more ground is exposed as the glaciers retreat, the landscape will become vulnerable to colonisation from plants and animals that currently can survive only at lower altitudes.

"If native species in the Pyrenees depend on glacial influences, you can imagine that they are going to be wiped off the map," Cauvy-Fraunie said.

The regional OPCC climate observatory estimated in a 2018 report that average maximum temperatures across the Pyrenees could rise by 1.4 to 3.3 degrees Celsius (2.5 to 4 Fahrenheit) by the middle of this century.

The increase has been even more dramatic at higher altitudes, where shrinking glaciers are seen as a harbinger of dire consequences across the range.

On the 2,870-metre (9,416-foot) Midi de Bigorre peak above the La Mongie ski resort—favoured by French President Emmanuel Macron—the average temperature has risen by 1.7 degrees since 1880, compared with a global average of 0.85 degrees, Moraine says.

Tourism affected

That could spell disaster for the roughly three dozen ski resorts on both the French and Spanish sides, as well as the popular stations in Andorra.

Already this year, around half of French resorts had to push back their scheduled openings before the Christmas holidays because of warm winds sweeping up from the south.

That came after a 2018-2019 season that saw the lowest snowfalls since regular measurements began 22 years earlier, according to the Meteo France weather service.

It took a heavy toll on tourism as lift ticket sales and hotel reservations plunged, with many skiers heading to higher slopes in the French Alps.

Already several glaciers have been reduced to little more than year-round snow packs, which will also impact the summer tourist season.

Rene said climbers will lose their "stepladders" for ascents to the highest peaks, "making their routes to the top more difficult".

And for hikers at lower elevations, the retreat will destabilise the newly exposed slopes, heightening the risk of rock falls or even avalanches.

Author: Herve Gavard | Source: AFP [January 20, 2020]