Prolonged warmth could be disastrous for the Greenland ice
The team focused on summer temperatures during periods of relative warmth, called interglacials, over the past 600,000 years.
The results of the study show that periods of prolonged warmth could be particularly disastrous for the Greenland Ice Sheet. Study co-author Dr. Elizabeth Thomas said that the findings are a warning for what we are experiencing today.
“What we see is that sustained summer warmth is associated with dramatic ice sheet mass loss,” said Dr. Thomas. “Today, we’re releasing greenhouse gases, causing Earth’s temperature to rapidly increase to levels last seen during these ancient warm periods.”
“Climate models show that if we continue emitting greenhouse gases at the current rate, there could be long-lasting effects that will keep the Earth’s temperature warm for thousands more years. We need to act now to dramatically reduce our emissions to minimize these potential, very long-term impacts.”
Over hundreds of thousands of years, sediments from southern Greenland have run off into the ocean, where they are carried to a location in the Labrador Sea called the Eirik Drift. Once they are settled in the ocean floor, the deposits accumulate in layers that hold a record of the geological past.
The scientists were specifically interested in the chemicals found in leaf waxes. The chemicals’ make-up changes ever so slightly depending on how warm or cool the region is, explained study first author Allison Cluett.
The results of the analysis revealed that summer temperatures in southern Greenland were elevated for about 20,000 years during a warm period that occurred roughly 400,000 years ago. During this time, scientists believe the Greenland Ice Sheet shrank substantially.
“Strong ice sheet retreat and forest cover in southern Greenland occurred during a period of sustained warmth about 400,000 years ago,” said Cluett. “Today, with global temperatures rising again, we could be on a similar trajectory if we don’t make reductions to greenhouse gas emissions. Our research really points to the importance of the duration of warmth for the ice sheet.”
The researchers noted that while potential scenarios on a scale of thousands of years may seem like a long time, actions taken over a brief period can have intense effects that reverberate far into the future, affecting generation after generation.
The team also used the sediment samples to reconstruct summer temperature trends for southern Greenland during four other interglacials.
“These are periods that are really difficult to study in the Arctic,” said Cluett. “That’s because as the ice sheets grow and wane, terrestrial records like lake sediments that could provide insight into environmental changes are often eroded away, so there’s very little information about what the climate was like during these past times, which may be our best analogues for future warming.”
The research was supported by the National Science Foundation (NSF).
The study is published in the journal Proceedings of the National Academy of Sciences.
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