Researchers compare global temperature variability during ice ages and interglacials – sciencedaily

Based on a unique global comparison of data from core samples taken from the ocean floor and polar ice caps, AWI researchers have now shown that although climate change has indeed diminished in the world between ice ages and interglacials, the difference is by no means as pronounced as previously assumed. Until now, it was believed that ice ages were characterized by extreme temperature variability, while interglacial periods were relatively stable. Researchers publish their advanced findings online in the journal Nature.

If you want to know how the climate will change in the future, you have to look at the past. By looking at the climate changes that took place thousands of years ago, we can improve predictions for the future climate. Comparing layers in ice core samples and ocean sediments allowed researchers to infer, for example, how the average temperature on Earth has changed over time, as well as the importance of variability. From the height of the last Ice Age 21,000 years ago to our current interglacial period, the Earth has warmed by an average of five degrees Celsius. In view of future global warming, it is vital for today’s global population to know whether temperatures will rise steadily or whether there will be sudden and significant fluctuations. The frequency of extreme events is an essential benchmark for climate change adaptation measures, because when it comes to flood protection, transport and building materials, we need to prepare for the worst-case scenario, and not just “medium” changes.

Climatology researchers from the Helmholtz Young Investigators Group ECUS at the Alfred Wegener Institute Helmholtz Center for Polar and Marine Research (AWI) in Potsdam have now investigated how temperature variability has changed as the Earth has warmed over the past period glacial to the present interglacial period. Temperatures to date have been assumed to vary considerably during the last glacial, while the current interglacial was largely characterized by small variations in temperature. This interpretation was based on water isotopic data from ice cores from central Greenland.

The team, led by Dr Kira Rehfeld and Dr Thomas Laepple, compared data from Greenland with sediment data collected from several ocean regions around the world, as well as from ice core samples collected in the Antarctic. They demonstrate that the phenomenon of large temperature fluctuations during ice ages was by no means manifested uniformly throughout the world, but rather varied from region to region. For example, in the tropics, temperature variations were three times more intense than today at the height of the last ice age, while ice cores from Greenland show variations 70 times more intense. “Greenland ice cores are undoubtedly an important key to understanding the climate of the past. That being said, our study confirms that the conclusions for Greenland are not always representative of the whole world, ”explains Laepple, leader of the Young Investigators Group. , who also heads the SPACE group of young researchers funded by the ERC.

The feat of first author Kira Rehfeld and her colleagues: for the first time they gathered and compared data from various climate archives and a total of 99 research sites. In the climate research community, ice cores are generally considered the gold standard because their layers are very cohesive, unlike layers of sediment on the seabed, which are frequently marred by tectonic changes, currents or marine organisms. AWI researchers have developed mathematical methods that allow them to estimate uncertainties and potential sources of error when evaluating various paleoclimate records, and to take these factors into account in their analyzes. “As such, we can compare sediment samples with ice cores for different epochs in the history of the planet,” says Laepple.

The more intense variations during ice ages are due to the greater temperature difference between the ice-covered polar regions and the tropics, which produced a more dynamic exchange of hot and cold air masses. “If we then follow this idea to its logical conclusion, it tells us that the variations will continue to decrease as global warming progresses,” says Rehfeld, simply because the temperature difference between the north and the warming tropics will decrease. “However, our data spans time periods spanning centuries and millennia – we can’t zoom in on just a handful of years, which means we can only draw indirect conclusions about the extreme events that shape time,” explains climatologist Rehfeld, who is currently pursuing research with the British Antarctic Survey (BAS).

Climate modelers had previously postulated the mechanism of reduced variability under warmer climate conditions in 2014. Yet, with their analysis, Rehfeld, Laepple, and colleagues are the first to bolster this theory with global climate data from the past. AWI researchers describe their next effort as follows: “We plan to study in detail changes in short-term variations in the past and their relationship to long-term climate change. To do this, we need reliable climate records and to improve our understanding of how they work. ”Increasing accuracy to a level at which paleo-records can also reflect extreme events will likely be one of the greatest challenges for researchers. years to come.


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Degradation of the North American ice cap has reduced climate variability in the southern hemisphere

Credit: CC0 Public domain

New research from the University of Colorado at Boulder shows that the changing topography of the ice caps in the northern hemisphere during the last ice age forced changes in the climate of Antarctica, a mechanism of interpolar climate change hitherto undocumented.

The new study published today in the journal Nature and co-authored by researchers at the University of Bristol, the University of Washington and UC Berkeley – suggests that a substantial reduction in the Laurentian ice sheet that covered much of present-day North America around 16,000 years ago resulted in significant climatic variations in the tropical Pacific and West Antarctica.

“The results demonstrate how effects apparently localized in one part of the world can have a significant impact on the climate elsewhere on Earth,” said Tyler Jones, associate researcher at the CU Boulder Institute for Arctic and Alpine Research (INSTAAR) and lead author of the new study.

Jones and his colleagues studied an ice core taken from the West Antarctic Ice Sheet (WAIS) to document the historic climate. The WAIS ice core is the first climate record to preserve year-to-year climate variability continuously 30,000 years ago.

“This ice core is really important because it contains long-term climate information that relates to the timescales humans experience and remember,” Jones said.

At INSTAAR’s Stable Isotope Lab, researchers slowly melted and then vaporized the ice cores for analysis using laser absorption spectroscopy, a new methodology that reveals the isotopic composition of water . This method improved the ability of researchers to measure climate change through ice cores, both increasing measurement resolution and saving time.

When the researchers examined the magnitude of year-over-year climate signals preserved in the WAIS core, they noticed a large and abrupt decline in signal strength about 16,000 years ago. They later determined that the anomaly was largely caused by the lowering of the Laurentian ice sheet.

“When there is a large ice cap over North America, the circulation of the atmosphere becomes very different from today,” Jones said. The new findings corroborate another published study suggesting that changes in the ice sheet over the same period altered the tropical Pacific climate enough to transform land ecosystems in present-day Indonesia from a grassy savannah to a rainforest, that they remain today.

Overall, the study points out that changes in Earth’s climate system can be linked over vast distances.

“No one has really studied this type of signal before. It potentially opens up new and exciting ways of thinking about climate data,” Jones said.


Massive volcanic eruptions in Antarctica linked to abrupt climate change in the southern hemisphere


More information:
TR Jones et al, Southern hemisphere climate variability forced by northern hemisphere ice cap topography, Nature (2018). DOI: 10.1038 / nature24669

Provided by the University of Colorado at Boulder


Quote: Degradation of the North American Ice Cap Decreased Climate Variability in the Southern Hemisphere (2018, February 5) Retrieved October 9, 2021 from https://phys.org/news/2018-02-north- american-ice-sheet-decreased.html

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Degradation of the North American ice cap has reduced climate variability in the southern hemisphere – sciencedaily

New research from the University of Colorado at Boulder shows that the changing topography of the ice caps in the northern hemisphere during the last ice age forced changes in the climate of Antarctica, a mechanism of interpolar climate change hitherto undocumented.

The new study – published today in the journal Nature and co-authored by researchers at the University of Bristol, the University of Washington and UC Berkeley – suggests that a substantial reduction in the Laurentian ice sheet that covered much of present-day North America around 16,000 years ago resulted in significant climatic variations in the tropical Pacific regions and in West Antarctica.

“The results demonstrate how effects apparently localized in one part of the world can have a significant impact on the climate elsewhere on Earth,” said Tyler Jones, associate researcher at CU Boulder Institute for Arctic and Alpine Research (INSTAAR) and lead author of the new study.

Jones and his colleagues studied an ice core taken from the West Antarctic Ice Sheet (WAIS) to document the historic climate. The WAIS ice core is the first climate record to preserve year-to-year climate variability continuously 30,000 years ago.

“This ice core is really important because it contains long-term climate information that relates to the time scales that humans experience and remember,” Jones said.

At INSTAAR’s Stable Isotope Lab, researchers slowly melted and then vaporized the ice cores for analysis using laser absorption spectroscopy, a new methodology that reveals the isotopic composition of water . This method improved the ability of researchers to measure climate change through ice cores, both increasing measurement resolution and saving time.

When the researchers examined the amplitude of year-over-year climate signals preserved in the WAIS core, they noticed a large and abrupt decline in signal strength about 16,000 years ago. They later determined that the anomaly was largely caused by the lowering of the Laurentian ice cap.

“When there is a large ice cap over North America, the circulation of the atmosphere becomes very different from today,” Jones said. The new findings corroborate another published study suggesting that changes in the ice sheet during the same period altered the climate in the tropical Pacific enough to transform terrestrial ecosystems in present-day Indonesia from grassy savannah to rainforest. , that they remain today.

Overall, the study points out that changes in Earth’s climate system can be linked over vast distances.

“No one has really studied this type of signal before. It potentially opens up new and exciting ways of thinking about climate data,” Jones said.

Co-authors of the new research include James White of CU Boulder and INSTAAR; William Roberts of the University of Bristol; Eric Steig and Bradley Markle of the University of Washington; and Kurt Cuffey of the University of California at Berkeley.

Source of the story:

Materials provided by University of Colorado at Boulder. Original written by Trent Knoss. Note: Content can be changed for style and length.


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