Water; ocean contents explained (Introduction)

by David Turell , Tuesday, December 17, 2019, 20:06 (1593 days ago) @ David Turell

A good review article. Its not just sodium chloride:

https://inference-review.com/article/reading-seawater

"The ocean is not merely a receptacle for inputs from rivers and volcanoes, but a dynamic medium whose chemistry is modulated by processes far more complex than previously imagined. The salt in seawater is now known to include more than 40 elements, ranging in concentration from gold at 0.00008 parts per million to sodium at more than 10,000 parts per million.

"Oceanographers classify these elements into three groups: conservative, scavenged, and recycled.17 Conservative elements, which include the major constituents of seawater, such as sodium and chlorine, have residence times on the order of millions to hundreds of millions of years. Their residence times are much longer than mixing times, the period over which they are distributed via waves, currents, and eddies. If an element’s residence time is greater than its mixing time, its concentration will be fairly uniform throughout the ocean, and it can be considered to have reached a state of chemical equilibrium in seawater.

"Recycled and scavenged elements have much shorter residence times, on the order of hundreds or thousands of years.18 As a result, there is insufficient time for these elements to achieve equilibrium through mixing, and their concentrations vary according to geography and depth. Scavenged elements include aluminum, lead, mercury, and other metals. These elements are attracted to the surfaces of fine clay particles and are exported from shallow waters as the particles sink to the ocean floor. The chemical concentration of scavenged elements decreases with depth in the water column.

"The recycled elements exhibit the most interesting and complicated behavior of all the groups. These are the ingredients essential for life, such as carbon, copper, iodine, iron, nitrogen, phosphorous, and zinc. In the uppermost region of the ocean where almost all sea life can be found, these elements are limiting nutrients, whose scarcity makes them coveted commodities in the marine biosphere. Any of these elements lost by one organism will be snatched up by another, keeping their concentration in the water itself low. Over time, a fraction of these nutrients leaks into deeper and relatively uninhabited waters, and so the concentration of recycled elements generally increases with depth.

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"Paleo-oceanographers now recognize that ocean chemistry has not remained strictly constant over time. The onset of the frigid Pleistocene epoch around 2.6 million years ago is thought to be linked to an increase in the salinity of the Atlantic Ocean as a result of the formation of the Isthmus of Panama. The isolation of the Atlantic from the less salty Pacific profoundly affected the global thermohaline circulation system, of which the Gulf Stream is one part.

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"From the very beginning, the history of life on earth has been intertwined with that of seawater. All the mass extinction events evident from the fossil record have been linked to variations in ocean chemistry, such as widespread acidification, anoxia, and associated perturbations to the carbon cycle. The demise of the dinosaurs, for example, can be attributed in large part to oceans poisoned by the constituents of the carbon and sulfur-rich rocks vaporized by the Chicxulub impactor. For this reason, some of the changes in ocean chemistry observed during the Anthropocene ought to give pause. The magnitude of these changes are comparable to the Great Dyings of the geologic past.23 If not tears or sweat, seawater could perhaps instead be considered earth’s blood, its composition a proxy for the health of the planet."

Comment: The oceans are part of many stabilizing processes like a carbon cycle. Oceans are complex just like all of the parts of Earth.