Shrubs Give an Insight into Glacier’s Past: Study

Scientists have discovered a new method of predicting a glacier's history of melting that can be extended way past the instrumental record. The new method involves carefully analyzing stems of the shrubs. Doing so can also provide an insight into how they're set to alter in the future.

Just the like rings on a tree stump denote the age of a tree, the width of the stem of a shrub indicates how well it has grown year on year. When shrubs breed in extreme environmental conditions such as the glaciers, their growth is dependent on the summer temperature, meaning the ring-width of a shrub can be used as a proxy for glacial melting, which also relies heavily on summer temperatures.

For this study, researchers from the University of Greifswald, tested this theory on a local icecap in the Scandic Mountains of southern Norway. They worked on 24 samples of shrubs from a site close to the glacier and analyzed their ring width.

 Lead author of the study, Allan Buras, said: "In warm summers, shrubs grow more compared to cold summers. In contrast, a glacier's summer mass balance is more negative in warm summers, meaning there is more melting compared to cold summers.

"Big rings in shrubs therefore indicate comparably warm summers, and thus a strongly negative summer mass balance in other words, more melting."

The local climate station from the Norwegian Meteorological Office provided details of the monthly precipitation and temperature. The summer mass balance of the glacier, from 1963 to 2010, was retrieved from the existing literature.

Each of these data sets was then statistically tested to see if there was a correlation between them. The researchers noticed a strong and dependable association between the ring-width of shrubs and the summer melting of glacier.

"Our results show that it is possible to reconstruct glacier summer mass balance with shrub ring-width series and it is therefore theoretically possible to extent records of summer mass balance into the past," Buras continued.

The shrubs that were collected in the study were relatively young, only allowing for reliable reconstructions over the past 36 years. This indicated that they could not be used to extend the record of the glacier; however, the researchers are confident that this could have been achieved if longer-lived shrubs were selected.

With the possibility of extending the instrumental records of summer mass balance, researchers may gain a better understanding of how glaciers behave in the summer, which they can use to calibrate and verify their existing models.

Their findings have been published Nov. 27 in IOP Publishing's journal Environmental Research Letters.