Snowball Earth melting led to freshwater ocean 2 kilometres deep | New Scientist
https://www.newscientist.com/...25-snowball-earth-melting-led-to-freshwater-ocean-2-kilometres-deep/
A little more than 600 million years ago, you could have drunk from the ocean.
After an extreme ice age known as snowball Earth, in which glaciers extended to the tropics and ice up to a kilometre thick covered the oceans,
the melt formed a thick freshwater layer that floated on the super-salty oceans.
Those freshwater surface seas lasted far longer than thought, according to research by Dorian Abbot, a geologist at the University of Chicago,
and his colleagues. Their mathematical models showed that it took around 50,000 years for the two layers to fully merge.
“This is interesting because the modern ocean mixes on a timescale of only about 1000 years,” says Abbot.
The much slower mixing was due to the huge density and temperature differences between the layers. During the snowball phase, half the oceans’
water ended up as snow and ice. The remaining seas were twice as salty as today, and near their freezing point.
Once the ice melted, driven by a runaway greenhouse effect caused by volcanic eruptions, it formed a freshwater layer up to 2 kilometres thick.