Ice sheets

As we focused our microscope on the soil sample for the first time, bits of organic material came into view: a tiny poppy seed, the compound eye of an insect, broken willow twigs and spikemoss spores. Dark-colored spheres produced by soil fungi dominated our view. These were unmistakably the remains of an arctic tundra ecosystem – and proof that Greenland’s entire ice sheet disappeared more recently than people realize. These tiny hints of past life came from a most unlikely place – a handful of soil that had been buried under 2 miles of ice below the summit of the Greenland ice sheet. Projections of future melting of the ice sheet are unambiguous: When the ice is gone at the summit, at least 90% of Greenland’s ice will have melted. Results of an ice sheet model show how much of Greenland’s ice sheet survives when the ice is gone from the Camp Century (white dot), GISP2 (red dot) and DYE-3 (black dot) ice...

Antarctica’s Thwaites Glacier got its nickname the “Doomsday Glacier” for its potential to flood coastlines around the world if it collapsed. It is already contributing about 4% of annual sea-level rise as it loses ice, and one theory suggests the glacier could soon begin to collapse into the ocean like a row of dominoes. But is that kind of rapid collapse really as likely as feared? A new study of Thwaites Glacier’s susceptibility to what’s known as marine ice cliff instability offers some hope. But the findings don’t mean Thwaites is stable. Polar scientist Mathieu Morlighem, who led the study, explains the results. Why is the Thwaites Glacier so important? Thwaites Glacier drains a huge area of Antarctica’s ice sheet – about 74,000 square miles (192,000 square kilometers), an expanse bigger than Florida. If a snowflake falls within that drainage system, it will eventually end up as part of an iceberg in the ocean off Thwaites....

My favorite place in the world isn’t a fixed location. It’s the JOIDES Resolution, an internationally funded research ship that has spent its service life constantly on the move, from deep in the Antarctic to high in the Arctic. Since 1985, scientific expeditions on this one-of-a-kind oceangoing laboratory have drilled 230 miles (370 kilometers) of sediment and rock cores – long cylindrical samples that provide a unique view of the ocean floor. The cores come from a thousand different locations, enabling scientists from many universities around the world to explore changes within the Earth. They also provide a window into our planet’s history. The ocean floor preserves a geological library that documents millions of years of climate change and evolution. The JOIDES Resolution leaves Honolulu in 2009. IODP/Wikipedia, CC BY Sadly, the JOIDES Resolution, also known as the JR...

About 400,000 years ago, large parts of Greenland were ice-free. Scrubby tundra basked in the Sun’s rays on the island’s northwest highlands. Evidence suggests that a forest of spruce trees, buzzing with insects, covered the southern part of Greenland. Global sea level was much higher then, between 20 and 40 feet above today’s levels. Around the world, land that today is home to hundreds of millions of people was under water. Scientists have known for awhile that the Greenland ice sheet had mostly disappeared at some point in the past million years, but not precisely when. In a new study in the journal Science, we determined the date, using frozen soil extracted during the Cold War from beneath a nearly mile-thick section of the Greenland ice sheet. A brief look at the evidence beneath Greenland’s ice sheet and the lessons its holds. The timing – about 416,000 years ago, with largely ice-free conditions last...