Unravelling ancient climates? It’s as clear as mud

Bosima is a species of water flea. Here, a single, semi-transparent flea is photographed against a solid blue background.

Unravelling ancient climates? It’s as clear as mud

Researchers use the information archived in lake-bottom sediments to fill in gaps in climate data from millennia gone by
November 29, 2015
Two researchers use a tool to examine sediment beneath a frozen lake so they can get information about environmental changes.
Sediments closest to the surface contain information about
environmental changes from the most recent decades.
These surface materials are obtained using a coring
device specifically designed to collect loose,
unconsolidated lake mud.
Jason Briner, University of Buffalo

No one in the 1970s could deny that certain lakes in Ontario were acid. But were they that way naturally or was their acidity the result of human activity? The only way to know would be to have reliable measurements of lake acidity from the pre-industrial 1800s to compare with present-day readings.

But no one was measuring acidity back then. Similarly, no one was recording what the weather was like tens of thousands of years ago. Some records go back a century, but many are only about 30 years old — nowhere near old enough for valid scientific comparisons that would enable climate scientists to determine whether today’s climate is truly unlike that of the past.

Luckily, it’s possible to go backwards in time to recreate a record of environmental change. John Smol, a Queen’s University biologist, does it by studying the mud at the bottom of lakes.

In this clip, John Smol explains why lakes are the best window to the past.

This scanning electron micrographimage shows a diatom known as Aulacoseira, which was preserved in the sediments of a lake on Baffin Island
This scanning electron micrograph
image shows a diatom known as
Aulacoseira, which was preserved
in the sediments of a lake on
Baffin Island.
Cheryl Wilson, Queen’s
University and Alexander Wolfe,
University of Alberta

By analyzing the information preserved in sediment and in the fossils buried within it — a field known as paleolimnology — Smol and his colleagues at the Queen’s Paleoecological Environmental Assessment and Research Laboratory can gather, with remarkable precision, the missing monitoring data. This information allows scientists to answer critical questions, such as when acid rain or industrial chemicals started affecting the water and ecology of lakes.

Further, once the historical data are known, scientists can start to figure out whether a problem stems from human activity or natural environmental change. And that can lead to solutions.

“Once you start understanding a problem, you can start mitigating the problem,” says Smol, who is the Canada Research Chair in Environmental Change.

Smol’s pioneering techniques have shed light on such issues as algal blooms and calcium decline in freshwater lakes, the evaporation of remote Arctic ponds caused by rising global temperatures and changes in the taste and odour of water in Ontario cottage-country lakes.

Main image: Bosima, a species of water flea, are well preserved in lake sediments. Credit: Jennifer Korosi, Queen's University

Originally posted June 2014