Patagonian Ice Holds the Key to Unlocking the Past

A research team recently conducted a study in the Northern Patagonia Ice Field (NPI) to uncover some of the mystery behind Earth’s ancient climate. Along the way, the team made important observations about the current state of glacial ice thinning and climate change.

Through their investigation of ancient paleoclimates (climates prevalent in the geological past), the scientists were able to identify time periods where major glacial growth and decline occurred in the Patagonian Ice Field, contributing important information to our understanding of our planet’s climate following the last ice age. Developing a strong comprehension of glacial advance and retreat over the last 10,000 years in places like the Patagonian Ice Field provides the scientific community with tools to augment our understanding of the past, as the planet’s climate is intrinsically related to its ecology at any given point in our recent geological history.

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An astronaut’s photo of a glacier outlet meeting a fjord in the Southern Patagonia Icefield. (Source: NASA)

Patagonia hosts a wide variety of largely untouched landscapes, possessing a range of environments from mountains and deserts to glaciers and grasslands. In addition to its mountainous beauty, the Northern Patagonia Icefield is special in that it is the most glaciated terrain on the planet within its latitude of 46.5 to 47.5 degrees south. The region where the ice field lies is a barren sector of South America spanning nearly 3 million square kilometers across southern Argentina and Chile.

In the glaciated terrain, thick layers of ice and rock hold a wealth of information regarding global climates of the last 25,000 years, offering a glimpse of where we are headed given the recent anthropogenic (human-caused) acceleration of climate change. The study provided scientists with valuable climate data from the Late Pleistocene and Holocene time periods, which began approximately 125,000 years ago following the final episode of widespread global glaciation.

The lead researchers of the study, David Nimick and Daniel McGrath, focused specifically on the the largest outlet glacier draining in the region, the Colonia Glacier on the eastern flank of the ice field. The team sought to constrain the ages of major glacial events by using a variety of dating techniques, including dendrochronology (tree-ring dating), radiocarbon dating, lichenometry (utilizing lichen growth to determine the age of exposed rock) as well as optically stimulated luminescence (dating the last time quartz sediments were exposed to sunlight). Employing such a wide variety of experimental techniques can be a valuable tool in improving the confidence of data and allowed the team to study a diversity of unique properties of the same glacial medium.  

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Lichen covered quartz ideal for lichenometry and luminescense. (Source: Tigerente/Wikimedia Commons)

By examining properties of lichen and quartz grains (when they were last exposed to sunlight), the research team was able to  constrain the time at which specific rocks were uncovered from the ice sheets. The age at which the ice melted away to reveal these rocks corresponds to events of retreat (and subsequent advance) of glacial ice across the last few millennia. The determination of major glacial events using these techniques sheds light on the climatic events that not only influenced South American paleoclimate but also may affect present and future glacial retreat given the recent spike in atmospheric carbon dioxide levels.

Results from dating analyses indicated that the most prominent increase in glaciated terrain occurred 13,200 years ago, 11,000 years ago and 4,960 years ago, with the last major advance defining the onset of Neoglaciation – the period of significant cooling during the Holocene or present day epoch. Analysis of a local ice-dammed lake revealed that glacial growth occurred 2,900 years ago and 810 years ago, with ice retreating during the intervening periods. This data points to the idea that in a general sense, warming and cooling even within the last 11,000 year Holocene interglacial period is highly cyclical. Significant Colonia Glacier thinning has been observed since the late 1800’s which has opened up low elevation channels for the local Lago Cachet Dos, a possible reflection of our warming climate and the greenhouse effect.

This knowledge provides an effective framework to which we can compare our actively changing climate. The timing between periods of glacial advance and subsequent retreat are useful metrics for judging the speed at which terrestrial ice is currently disappearing.

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Glacial ice melts as it floats in a region north of the NPI. (Source: Adam Derewecki)

Nimick’s team’s findings show advance of the Colonia Glacier occurring approximately every 1,000 years under a climate with generally stable atmospheric carbon dioxide levels. Given the recent benchmark event of passing the 400ppm atmospheric carbon dioxide threshold, it is undeniable that human activity, particularly in the form of carbon emissions, is altering global climate and atmospheric carbon dioxide levels.

As we continue to release more carbon dioxide into the atmosphere, the stable conditions that contributed to the glacial patterns discovered in the study may no longer be present. Increases in greenhouse gases and a warming planet may spell disaster for ice sheets, yet the current speed and extent of glacial melting remain uncertain. Nevertheless, understanding glacial patterns in the Northern Patagonia Ice Field has improved our understanding of paleoclimate following the last ice age and may in fact contribute to our ability to improve forecasts for glacial retreat in the coming years.

Melting Glaciers, Changing Careers

Ice core drilling. Credit: Doug Clark, Western Washington University
Ice core drilling. Credit: Doug Clark, Western Washington University

Climate change is making the work of glaciologists complicated. Scientists that study paleoclimatology of the Earth have come to the realization that melting ice and receding glaciers are getting in the way of their fieldwork.

“Time no longer starts at the surface,” said Lonnie Thompson, a paleoclimatologist at the Byrd Polar Research Center at the Ohio State University in Columbus, in an interview with Nature.

His ice-core research career started since the mid-1970s. When he drilled an ice core from the Quelccaya ice cap in the Peruvian Andes in 1983, melting had not occurred at altitudes above 5,000 meters. However, 20 years later when he returned for another ice core, things changed completely—melting disrupted the pattern of atmospheric isotopes in the top 40 meters of ice.

Peruvian Andes. Source: Flickr.
Peruvian Andes. Source: Flickr.

To address challenges like those faced by Thompson, the community of ice-core researchers is developing a better approach to saving ice for the next generation of scientists. Patrick Ginot, a paleoclimatologist at the Institute of Research for Development (IRD) in Marseilles, France, advocated that the United Nations Educational, Scientific and Cultural Organization (UNESCO) support a program that would sustainably collect ice cores and store extra samples at the Concordia Research Station in central Antarctica, in order to meet the research demands for both current and future scientists.

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Concordian Research Station in central Antarctica. Source: European Space Agency.

The layers in an ice core are a reliable indicator of its age. Scientists and researchers count the layers that record seasonal changes and date ice cores. Ideally, an intact ice core shows the most recent year on the top layer, which scientists use to link to their knowledge about recent climate conditions—temperature, precipitation, etc.

For example, the nuclear tests in 1950s and 1960s, as well as the 1986 Chernobyl disaster, left datable signatures in glaciers all over the world, which mark specific years for scientists. Stable isotopes of oxygen that remain in partially melted ice could enable scientists to obtain average measurements from 5- to 10-year periods, though not year-to year data. Unfortunately, ice core samples with insufficient radioactive signature make it difficult for researchers to identify specific years.

To acquire a pure sample of ice core, glaciologists have no choice but climb higher where melting has not yet begun, though it can be dangerous.

“In most cases, we can’t go higher. We can’t get to a colder environment,” said Douglas Hardy, a geoscientist at the University of Massachusetts Amherst, in an article in Nature. He once placed weather instruments on glaciers to measure temperature, humidity, precipitation rates and the amount of sunlight that shed on the surface of glaciers. These meteorological conditions can help scientists examine the impacts of these factors on layers of ice.

Now, Hardy explained, scientists have to do the work before the ice is gone permanently, otherwise glacier history will remain unknown forever. The pathway to higher altitudes is worthwhile, but risky at the same time. Therefore, collecting and storing ice core samples before they all melt away seems a good solution to the problem.

The major challenge of storing ice cores lies in funding, as most science funding agencies tend to pay for research that is expected to generate quickly published results.

To persuade donors, the International Partnerships in Ice Core Sciences prepared a report on the importance of preserving records of climate history. The co-chair of the organization, Ed Brook, expects to present the report on a major geosciences meeting in 2016.

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The Association of Polar Early Career Scientists (APECS) organizes events to support young polar scientists researchers. Source: APECS.

Younger scientists also expressed their uncertainty of future ice-core research. Aron Buffen, a paleoclimatology doctoral student at Brown University says that scientists will easily lose comparisons for future measurement techniques if all the ice melts quickly.

On the other hand, Buffen also points out that the melting may bring about more research questions, such as distinguishing between melting caused by warming and sublimation caused by lower humidity. If scientists can shed light on how glacier retreat impacts local ecosystems, the research can be used to help communities better adapt to climate change. Additionally, organizations like the Association of Polar Early Career Scientists (APECS), are helping young glacier researchers develop their career paths and networks in an innovative, international and interdisciplinary approach.

While grieving over the disappearing glaciers, scientists can also see the silver lining as intriguing opportunities arise from the perspective of careers and science.