Inside the Race to Rescue Clues to Earth's Past from Melting Glaciers

    A. Margit Schwikowski and her team were attempting to drill into the Corbassière glacier in the Swiss Alps when the weather started to turn. They were camped among the soaring peaks of the Grand Combin mountain chain. The only way off this vast sheet of ice in a storm is to descend a steep mountain wall or go across the jagged glacier surface itself, which claims several lives a year. Instead, they retreated by helicopter before it was too late.
    B. For Schwikowski, an environmental chemist at the Paul Scherrer Institute in Villigen, Switzerland, the risks of missions like this October 2020 expedition to Corbassière are worth it. The team she was leading is part of an international enterprise that aims to preserve the 'memories' frozen into mountain glaciers across the world, by drilling out long samples all the way from the young surface snow down to the old, compacted ice at the base of a glacier.
    C. These ice cores are loaded with information about Earth's past that could be crucial in our fight against global warming. Locked within them is a picture of how the planet's climate has changed over time, as well as evidence of human activity as far back as the Romans, clues about the evolution of microorganisms (微生物) and much more. Now, scientists are racing rising temperatures to rescue ice cores from the world's glaciers before they melt.
    D. Mountain glaciers, also known as alpine glaciers, are slow-flowing rivers of ice. They begin life at high altitudes where the amount of snow settling in winter significantly exceeds the amount that melts in the summer. Over time, the snowpack builds up and the overlying weight causes snowflakes in the deeper layers to gradually transform into blue-tinted glacier ice, which eventually creeps downhill under its own weight.
    E. 'Deep within glaciers there is an amazing process, where ancient air is preserved from the time when it became trapped in the ice,' says Schwikowski, describing an effect of the increasing density with depth. This critical depth where not even air can escape is around 45 metres in the European Alps. The trapped air is just one relic that will be lost forever if sample ice cores aren't gathered before the glaciers melt. Schwikowski and her team are rushing to extract samples from the planet's most vulnerable glaciers.
    F. Sadly, in the case of the Corbassière glacier it is already too late. Even before the weather turned, the mission was scuppered (使泡汤). At each attempt to extract an ice core, the scientists hit a hard layer known as an ice lens. These form when glacier surface layers melt, causing water to percolate (渗入，渗透) through the snow, before refreezing into a thick ice sheet below. With the chronology of ice layers mixed up like this, valuable scientific information is lost forever.
    G. It is a similar story across the world. Glaciers are shrinking at alarming rates. More than 9 trillion tonnes of glacier ice was lost between 1961 and 2016, adding 27 millimetres to the average global sea level, according to a 2019 study led by Michael Zemp, director of the World Glacier Monitoring Service. If current melting rates continue, glaciers will vanish entirely from Europe, New Zealand and the west of North America, among other parts of the world, by the end of the century.
    H. The result will be a further rise in sea levels globally, with all the knock-on effects for people, especially those living near coasts and in rural communities that rely on water from seasonal ice melt. For scientists like Schwikowski, the melting of the glaciers also endangers an unparalleled archive in the ice of Earth's environmental past, prompting the launch of the Ice Memory project in 2015. 'These archives are formidable records of our past and they must be preserved for future generations of scientists,' says Carlo Barbante, a chemist at the University of Venice, Italy, and a co-founder of the project.
    I. Geologically speaking, mountain glaciers hold a fairly young ice record, typically spanning the past 1,000 to 10,000 years. One thing they can't do is build a picture of the really long-term climate. For this, scientists mostly rely on older ice samples from continental ice sheets in Antarctica and Greenland. These are also threatened by global warming, but their shrinkage (缩小，收缩) will occur over thousands of years, so they are beyond the scope of the Ice Memory project. Although younger, mountain glaciers have one major advantage over the ice sheets—their geographical spread. They exist on all continents except Australia. This helps us to build a truly global picture of relatively recent past climates and means the information they contain is also highly region-specific.
    J. It may even be possible to unpick some of the impact of past changes in climate on ecosystems. One way to do that is through the microorganisms stored inside mountain glaciers. Traditionally, investigations of ice-dwelling microbes involved growing them from field samples, which favoured certain 'lab-happy' microorganisms. However, genetic sequencing technologies are bypassing this requirement, enabling biologists to gain a more complete picture of glacial ecosystems directly from the field samples themselves.
    K. Eager not to miss out on these clues to the past, researchers involved with the Ice Memory project have fanned out across the world to gather samples. In 2016, the launch mission extracted three ice cores from the Col du DSme glacier at an altitude of 4,300 metres on Mont Blanc in France. Since then, cores have been extracted in 2017 from the Illimani glacier in Bolivia—where glaciers hold records dating back 18,000 years—and from two sites in Russia during 2018. The plan is to extract cores from a further 20 sites across the world over the next 10 to 15 years.
    L. The scientists drill near the highest points of glaciers, where snow and ice accumulates, rather than lower down the glacier tongue, where downhill flow mixes the ice record. But nature doesn't always play ball. Patrick Ginot at the Institute of Environmental Geosciences (IGE) in Grenoble, France, who led the Bolivia mission, recalls battering winds and heavy snowfall for two weeks at 6,300 metres above sea level. 'There were days on the summit of Illimani when we could not work at all.'
    M. Battling the elements isn't the only challenge for these expeditions. There are logistical hurdles to navigate, too. The scientists need permits from governments, local assistance with transport and a reliable refrigeration chain to ensure that samples don't melt. These local partnerships are an essential element of Ice Memory. Project scientists are acutely aware of the damage that could be done by European scientists 'parachuting in' to less scientifically developed nations to extract samples for the benefit of their careers. 'Our way is always to start by building a collaboration with local scientists and then to organise the operation from there,' says Ginot.
    N. Even after all this, retrieving the ice cores is only half the battle, as they also need to be stored. The plan is to house them in a purpose-built 'ice sanctuary' facility at the French-Italian Concordia Research Station, more than 1,000 kilometres inland from the south-east coast of Antarctica. The location was chosen for being politically neutral and reliably cold over the long term, so there is no threat of freezer failure wiping out millennia of data. Schedules have been stalled by the COVID-19 pandemic, but the first cores could reach the ice sanctuary as early as 2023.  

    Glaciers all over the world are melting at amazing speed, on the verge of complete disappearance.

    In order to gather ice samples in countries where science is less developed, project scientists need to establish a partnership with scientists there at the beginning.

    Nature isn't always satisfactory, with bad weather impeding the research progress sometimes.

    Scientists can't get a picture of climate change that occurs over 10,000 years by investigating ice samples in mountain glaciers.

    Every year, some people lose their lives on their way to escape from the Corbassière glacier when the storm comes.

    Researchers involved with the Ice Memory project have collected samples all over the world, longing for preserving the evidence of past climate changes.

    The life of coastal and rural populations will be greatly affected by a further rise in sea levels, which results from continuous melting of glaciers.

    Scientific evidence in these ice cores disappears permanently because of the repetitive process of glaciers' melting and freezing.

    The scientific information in ice cores can tell us about Earth's past, which plays a vital role for us to battle with global warming.

    Ancient air is sealed and conserved in the depths of glaciers.