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Researchers track changes in Greenland ice core dust over the past 100 years

Released on September 28, 2021 (in Japanese)
Posted on November 9, 2021

The Holocene epoch (from about 11,000 years ago to today) has been a period of low dust concentration, making it hard for dust in ice core samples to be used for geochemical analyses over the past 100 years. But Japanese researchers have applied a relatively new technique to analyze ice core samples from Greenland covering the past century for the first time, enabling a temporal resolution of increments of just five years.

SEM images of each mineral group in the SIGMA-D ice core.
Nagatsuka N., et al. Clim. Past, 17, 1341–1362, 2021, doi: 10.5194/cp-17-1341-2021

For the first time, researchers have been able to discover the pattern of mineral composition of dust in ice core samples from Greenland over the past 100 years and at a resolution of increments of just five years. Previously, similar analyses had been unable to achieve a resolution shorter than hundreds of thousands of years due to the need for greater concentrations of isotopes in the minerals in the dust.

The technique and findings are described in a paper appearing in the journal Climate of the Past on June 21.

Dust blown by the wind and landing on snow and ice on ice sheets (massive continental glaciers covering much of Antarctica and Greenland) that collects over time can provide rich information about the past when retrieved in ice cores by scientists.

These ice-core dust records have provided substantial data on variations in the concentration, composition, particle size and shape (morphology) of the minerals that make up dust particles, which in turn can tell us much about where they come from and thence about historic climate change. This is because the variability in the dust over time is affected by changes in the terrestrial sources of the dust and atmospheric transport of dust as a result of temperature changes.

However, such work has primarily been performed by researchers on dust minerals covering timescales on the order of the swings between glacial and interglacial periods (in essence, ice ages and the warmer periods between them)—roughly about 800,000 years.

This is because geochemical analyses of the minerals in the dust depend upon the ratios of different isotopes of elements such as strontium, neodymium and lead. The isotopic ratios in a sample have strong regional variations controlled by their geological origins, and so can help tell us a dust particle’s geographic origin.

However, isotopic analyses require a large number of samples, and so researchers have mostly used ice core dust from glacial periods where there has been a high dust concentration. But the Holocene epoch (from about 11,000 years ago to today) has been a period of low dust concentration. As a result, each sample for this period has required thousands of years’ worth of deposition of ice just to gather enough dust to do the analysis. This is useful for descriptions of changes of long periods of time, but not for changes over the last century.

In recent years, two techniques, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), have enabled scientists to reveal the source of ice core dust samples with low amounts of mineral dust. The first technique gives them morphological information about the minerals (in essence their shape) as a whole rather than the isotopes of the atoms within them, and EDS tells them about the mineral composition of individual dust particles.

“SEM-EDS analysis has been demonstrated to deliver a high temporal resolution record of the composition and sources of ice core minerals, which is a great improvement over earlier techniques,” said Naoko Nagatsuka, a researcher with Japan’s National Institute of Polar Research and lead author of the study.

“But it has only been used for two or three ice core analyses. Variations in the dust properties of Greenland ice cores for recent years have remained largely unknown.”

The team used SEM-EDS analysis to describe variations in the sources of minerals in dust from a Greenland ice core covering a century-long period (1915-2013), and with a resolution of just five years.

They found that the composition varied substantially over the decades. Kaolinite, a clay mineral that tends to form in warm and humid climatic zones, was abundant in the core during colder periods over the past century. Meanwhile quartz, chlorite, mica, feldspars and mafic minerals (those with higher concentrations of iron and magnesium)—grains of which are weathered and eroded from rock in more arid, high-altitude regions and also from more local areas in Greenland—were abundant in warmer periods.

Comparison of this information to Greenland surface temperature records indicates that this multi-decadal variation in the relative abundance of these different minerals was likely affected by local temperature changes on the island. The minerals were transported mainly from its west coast during the two warming periods (1915-1949 and 2005-2013). This, in turn, was likely due to an increase in dust sourced from ice-free areas due to a shorter duration of snow and ice cover in Greenland’s coastal region during the melt season caused by recent global warming. Meanwhile, the researchers reckon that ancient deposits from northern Canada, which were formed in past warmer climates, are the best candidate for the geographic source of minerals that landed on Greenland ice sheet during the colder period (1950-2000).

The researchers now want to extend this technique for detecting variations in ice core dust sources during recent periods of low dust concentration to other parts of Greenland and beyond.

Original article:

Journal: Climate of the Past
Title: Variations in mineralogy of dust in an ice core obtained from northwestern Greenland over the past 100 years
 Naoko Nagatsuka (National Institute of Polar Research, Japan)
 Kumiko Goto-Azuma (National Institute of Polar Research, Japan)
 Akane Tsushima (Chiba University, Japan)
 Koji Fujita (Nagoya University, Japan)
 Sumito Matoba (Hokkaido University, Japan)
 Yukihiko Onuma (University of Tokyo, Japan)
 Remi Dallmayr (Alfred Wegener Institute, Germany)
 Moe Kadota (Hokkaido University, Japan)
 Motohiro Hirabayashi (National Institute of Polar Research, Japan)
 Jun Ogata (National Institute of Polar Research, Japan)
 Yoshimi Ogawa-Tsukagawa (National Institute of Polar Research, Japan)
 Kyotaro Kitamura (National Institute of Polar Research, Japan)
 Masahiro Minowa (Nagoya University, Japan)
 Yuki Komuro (National Institute of Polar Research, Japan)
 Hideaki Motoyama (National Institute of Polar Research, Japan)
 Teruo Aoki (National Institute of Polar Research, Japan)
DOI: 10.5194/cp-17-1341-2021
Published Online: June 21, 2021


This research has been supported by the Japan Society for the Promotion of Science (JSPS) Fellowship (SIGMA project (grant nos. 23221004 and 16H01772) and 15H01731, 15K16120, 16J08380, 16H06291, 18H03363, 18H04140, 19K20443, 20H04980), the Integrated Research Program for Advancing Climate Models from the Ministry of Education, Culture, Sports, Science and Technology (MEXT, Japan (grant no. JPMXD0717935457)), the Arctic Challenge for Sustainability (ArCS (grant no. JPMXD130000000)), the Arctic Challenge for Sustainability II (ArCS II (grant no. JPMXD1420318865)), the Environment Research and Technology Development Fund of the Environmental Restoration and Conservation Agency of Japan (grant nos. JPMEERF20172003 and JPMEERF20202003), and the National Institute of Polar Research, Japan, through project research no. KP305.

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