Chemical Oceanography

  • Mono Lake is studied by chemical oceanographers as a modern analog for ancient oceans.

Why is the sea salty? That’s probably the first chemistry question we ask our students in Introduction to Oceanography. Some ancient folk tales will have you believe that the source of the salt is a magic mill that was accidentally dropped on the bottom of the sea where it continues to crank out salt. Turns out there is some truth to these folk tales, only that the 'magic mill' is on land, not in the ocean. Mountains are ground down to a fine powder through a grab bag of processes we collectively refer to as weathering. What is left of the rocks is washed into the sea and makes it salty. Weathering is only one of the many reasons why marine chemistry and geology are inextricably linked. Nutrients and carbon often enter the ocean from land, as well as being formed in the ocean itself. Their distribution determines where in the ocean biology can thrive and in turn, their uptake and use by organisms impacts their distributions. The ocean contains 50 times more carbon than the atmosphere, owing to the ease with which CO2 reacts with water and therefore plays a vital role in absorbing much of the anthropogenically produced CO2. But the ocean's capacity to absorb this 'surplus' carbon is not limitless, and the addition of CO2 can be harmful to some organism such as corals. The sediments are the ultimate resting place for anything that enters the ocean, after it has been churned over countless times by chemical, physical and biological processes. Who would have thought that we can learn from old folk tales and fables—Hansel & Gretel anybody?