The study may have responded to the mystery of the young, weak sun, which shone 20% brighter in archaic times. Although the Sun burned 20% brighter on primitive Earth, fossil evidence suggests that our planet had warm, shallow oceans where stromatolites, microbial mats, flourished.
New research could have solved the “problem of the young, weak sun,” showing that saltier waters could have prevented the Earth from freezing more than 3 billion years ago.
(Photo: Photo by JOHAN ORDONEZ / AFP via Getty Images)
We all know that the composition of the atmosphere (especially the concentration of greenhouse gases) is essential for regulating the temperature of the Earth, but what about the composition of the oceans? To study the influence of salinity, the researchers used a model of general circulation of the oceanic atmosphere.
They show that saltier seas result in warmer temperatures, in part because salt reduces the freezing point of salt water and limits the development of sea ice, but mostly because salt water has a higher density, which modifies ocean circulation patterns and promotes heat transit to the poles.
According to its archaic scenario, current salinity levels result in a very glacial globe with only a small strip of open water near the equator. However, increasing salinity by up to 40% more than today indicated warmer Archean soil with typical surface temperatures of more than 20 degrees Celsius with ice only reaching the poles seasonally. Geophysical Research Letters published their findings.
Read also: The study shows how much methane is released from ocean fjords
Why is the ocean salty?
(Photo: Photo by Mario Tama / Getty Images)
The ocean draws its salt from two places: the excess of the earth and the openings at the bottom.
Terrestrial rocks are the main source of salts dissolved in salt water. Because rainwater on the ground is slightly acidic, it erodes the rocks. This causes ions to be released into streams and rivers, which eventually flow into the ocean. Many of the dissolved ions are taken from the water by ocean creatures. Others are not eliminated, which causes their concentrations to increase over time.
Hydrothermal fluids, which arise from seabed respirators, are another source of salts in the ocean. Ocean water seeps through cracks in the seabed and is heated by magma from the Earth’s core. Heat initiates a chain of chemical reactions. Water tends to lose oxygen, magnesium and sulfates while absorbing metals such as iron, zinc and copper from the surrounding rocks.
The heated water is expelled through the ventilation ducts of the seabed, carrying the metals. Some ocean salts form due to underwater volcanic eruptions that directly discharge minerals into the ocean.
What if the ocean froze?
The composition of the atmosphere, especially the concentration of greenhouse gases, is well known to impact the Earth’s climate system. We show, using a climate model, that the composition of the ocean can significantly influence surface temperature and ice cover. We focus on the amount of salt dissolved in seawater and discover that saltier oceans result in warmer climates.
These effects are minor today, but salt may have been an important component of early Earth’s habitability when the Sun was less bright.
The ice blanket covering the oceans would block most of the light into surface water. This would destroy seaweed, with the consequences that reverberated in the food chain until the seas were almost barren. Only deep-water species living near hydrothermal vents could survive.
Because ice reflects more sunlight than water, the global climate would decrease dramatically, causing the earth to freeze. Plants would die from lack of water, which would lead to a reduction in CO2 uptake; thus, CO2 from volcanoes would slowly accumulate in the atmosphere and reheat the earth, although thawing the ice could take millions of years.
Related article: Climate change affects the composition of the ocean, making it difficult for sea creatures to communicate
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