Ice sheets can retreat as much as 600 meters per day during warm periods, a pace twenty times faster than the quickest retreat ever measured. This finding comes from a new study published in Nature.
An international team led by Dr. Christine Batchelor of the University of Newcastle, England, used high‑resolution seafloor imagery to confirm how rapidly an ancient ice sheet stretched from Norway at the end of the last Ice Age, around 20,000 years ago. The team then explored what those past dynamics could imply for today.
The method used to uncover the story
The researchers, including collaborators from the Universities of Cambridge and Loughborough in the United Kingdom and the Norwegian Geological Survey, mapped more than 7,600 small seafloor landforms known as ripple ridges. These ridges are under 2.5 meters tall and sit 25 to 300 meters apart.
The ridges are believed to form when the edge of the retreating ice sheet rises and falls with the tides, lifting seafloor sediments into a hill with each tidal cycle. Two ridges would form each day due to two tides daily, allowing researchers to gauge the ice sheet’s retreat speed.
The results show the old ice sheet retreated at a rate between 50 and 600 meters per day, far faster than other observed ice sheets measured from satellites or inferred from similar formations in Antarctica.
Dr. Batchelor notes that this work serves as a warning from the past about how quickly ice sheets can pull back. The findings indicate rapid recoil pulses can exceed all previously observed rates.
Understanding ice sheet behavior during prior warm periods helps refine computer simulations that project future changes in ice mass and sea level.
Co-author Dr. Dag Ottesen from the Norwegian Geological Survey emphasizes the value of high‑resolution images of glacial landscapes preserved on the seafloor.
New findings show that such rapid retreat episodes can be very short, ranging from days to months.
Cambridge University professor Julian Dowdeswell, a co-author, explains that average retreat rates over multi‑year periods can hide brief, pulsed episodes of faster retreat, describing this behavior as a rapid burst in ice dynamics.
The shapes found on the seafloor also illuminate how such brisk retreat might occur. Batchelor and colleagues discovered that retreat accelerated along flatter sections of the bed.
Frazer Christie explains that an ice floe can break away and retract almost instantly once it becomes buoyant, a retreat pattern that appears primarily on relatively flat beds where less melting reduces the overlying weight needed for flotation.
Could this happen soon in Antarctica
The researchers suggest that a similarly fast pulse could already be occurring in parts of Antarctica. The vast Thwaites Glacier has drawn international attention because of its potential sensitivity to unstable retreat in West Antarctica. The study proposes that Thwaites may be experiencing a rapid retreat pulse as it recently moved across a flat area of its bed.
The team notes that current snowmelt rates could trigger brief flashes of rapid rebound in flat regions of the Antarctic ice sheet, including Thwaites. They also suggest that satellites could soon detect such ice sheet retreat if the warming trend continues.
Reference work: Nature 2023 05876 1
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