The Whole Story of Climate by E. Kirsten Peters

Author:E. Kirsten Peters
Language: eng
Format: epub
Publisher: Prometheus Books
Published: 2012-11-20T05:00:00+00:00

Some glacial ice is pretty filthy stuff. True, there are a few glaciers that are made of clean and beautifully blue ice—the ones that show up pictured in advertisements. But much glacial ice is packed full of silt, sand, pebbles, and even boulders the size of trucks and houses. As summer visitors to alpine glaciers know, when a glacier is melting backward up its valley, the terminus area is made of loose silt, sand, and jumbled rocks of all sizes. When the wind blows, as it does in the mountains quite a bit, such areas are no place to picnic—and no picnic for doing careful scientific measurements or even keeping clothes halfway clean. Silt and sand blow around until a calm afternoon arrives, allowing geologists and hikers alike to amble below the glacier without grit in their teeth—at least for a few hours.

It was the many rocks embedded in Pleistocene glaciers that scoured the solid Earth and created the deep, majestic valleys of Yosemite and the Alps. Because of such abrasion, the rocks in glacial ice end up with the striations Louis Agassiz noted. And it turns out that the same glacial grit gave scientists their first clear evidence of a climate cycle that repeats about every six to seven thousand years.

In the later decades of the twentieth century, many geologists still looked at rocks on land in the old-fashioned way of walking over them, hammer in hand, and bashing off pieces of outcrops. That's how geologists are trained, and some of us never graduate beyond it. But other geologists, increasingly known as marine geologists, had also appeared on the scene. They worked in groups from ocean-going research vessels and drilling platforms, funding their expensive science via major grants from national and international institutions.

We cannot fully explain the findings of marine geologists in terms of a single person—like Agassiz or G. K. Gilbert—because their work had to be collaborative, simply due its nature. It takes many hands to do research from a ship. But even in a field dominated by teams and groups, some specific results and some individual researchers stand out. One geologist of this sort had the imposing name of Harmut Heinrich. In the late 1980s, Heinrich was a young professional, just starting out in science. He jumpstarted his career with a bang by publishing the results of his pioneering work looking at layers of sediments on the seafloor of the North Atlantic.

The floor of the sea, not surprisingly, is covered in fine sediment that has settled down from the water column above it over vast amounts of time. The deeper you core into the seafloor sediments, the older the material. What Heinrich found in the seafloor sediments of the North Atlantic was both clear and quite startling. At regular intervals, the layering of the deep seafloor was littered with small rock debris of many different types and sizes, the kind of material geologists would clearly and immediately recognize as originating in glaciers.

At first blush, it may be difficult to see the relationship between the deep seafloor and glaciers on land.

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