Frozen solid -- Warming, Expanding, Polluted & Acidified

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Snowball Earth

Long before the explosion of multicellular life in Earth’s oceans, a half billion years ago, those oceans were covered in ice meters thick. Beneath that ice, darkness reigned, and photosynthetic organisms fell silent (there were no animals back then).

Snowball Earth, is how geologists describe the planet back then. Joe Kirschvink, a geophysicist at the California Institute of Technology, pioneered the concept in the early 1990s.

Viewed from the moon during the Cryogenian and early Ediacaran periods of the Neoproterozoic Era of Earth time, between about 720 and 640 million years ago, Earth would have shone like a snowball.

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Two pan-planetary glaciation events have been documented — the Sturtian, from about 720 to 660 million years ago (mya), and the Marinoan, between about 645 and 640 mya.

Take a close look at the top right of this chart

Last week, the Canadian scientist who popularized Joe Kirschvink’s idea, helping to overcome widespread skepticism, gave a talk at McMaster University, in Hamilton, Ontario.

Having earned a geology degree from McMaster University in 1964, Paul Hoffman worked for the Geological Survey of Canada for a while, studying Proterozoic geology across Canada’s north, then moved on to the School of Earth and Ocean Sciences, at the University of Victoria. Hoffman is now Sturgis Hooper Professor Emeritus of Geology at Harvard University.

I interviewed Paul Hoffman back in the early 1990s, for my Earth Chronicles series.

At the time, Proterozoic carbonates and the involvement of plate tectonics in Earth’s early history were his area of specialty. Hoffman was aware of Joe Kirschvink’s Snowball Earth idea, but never dug down into the details. In the course of geology fieldwork in northern Namibia, studying the relative proportion of carbon isotopes in polished rock, his interest would grow enormously.

When I heard Paul Hoffman would be giving a talk at Mac about Snowball Earth, I registered. Hoffman’s mid-June presentation to a roomful of Mac grads — reviewing evidence for Snowball Earth from the fields of geochemistry, paleoclimatology, biology, and molecular phylogeny — was both engaging and intellectually challenging. Afterward, Hoffman accompanied me to the studios of CFMU, where we sat down for a talk about Snowball Earth.

Listen to our conversation in today’s podcast. Click on the play button above, or go here.

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Listen to our complete conversation here:

California tide pool (David Kattenburg)

Then there’s the status of Earth’s oceans today. Largely liquid, they’re in a sorry state.

Seventy percent of Earth’s surface is covered in ocean. Currently pegged at 8.4 billion – and growing – human populations have wreaked havoc on Earth’s oceans, filling them with chemical pollutants, monumental volumes of plastic, and megatons of terrestrial sediment.

A third of the CO2 humans have pumped into the atmosphere over the course of the last 200 years has ended up in the oceans, acidifying them. Ocean acidification is throwing ocean carbonate chemistry out of balance, disrupting the ability of shell-forming plankton to build their shells.

Ninety percent of CO2-generated atmospheric heat has also ended up in the oceans, expanding them.

The reported doubling of the rate of sea level rise, largely due to thermal expansion, threatens coastal communities around the world. Over a third of humanity lives within a hundred kilometers of the coast, within meters of the ocean’s rising surface.

Alongside their physical structure and chemistry, the biological diversity of Earth’s oceans is taking a hammering.

Impacts on coastal salt marshes, seagrass meadows, mangrove forests, coral reefs, and iconic marine mammals are easy to observe.

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Much less evident are the extraordinary communities of free-floating plant and animal plankton, and soft-bodied benthic (bottom-dwelling) organisms inhabiting the depths of open ocean, especially on the walls of submarine ridges, seamounts, abyssal plains and incomprehensibly deep trenches.

Research continues to highlight the extraordinary lives of creatures few if any humans have ever observed.         

If Earth’s ocean creatures are in trouble, so are humans. But ocean experts are hopeful. Oceans need to be managed more effectively.

The GPM spoke about this with Rafael Gonzalez-Quiros, joint coordinator of a group of ocean experts, and co-author of the UN-affiliated Third World Ocean Assessment.

Listen to our conversation in today’s podcast. Click on the play button above, or go here.

Listen to our complete conversation with Rafael Gonzalez-Quiros here:

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