Salinity and Ocean Chemistry
Salinity refers to the concentration of dissolved salts in ocean water, primarily sodium chloride. It plays a crucial role in ocean chemistry, influencing water density, circulation, and marine life distribution. Variations in salinity result from processes like evaporation, precipitation, river inflow, and ice formation or melting. Ocean chemistry encompasses the study of all dissolved substances, including nutrients and gases, which together regulate Earth's climate, support ecosystems, and drive biogeochemical cycles in the oceans and seas.
Salinity and Ocean Chemistry
Salinity refers to the concentration of dissolved salts in ocean water, primarily sodium chloride. It plays a crucial role in ocean chemistry, influencing water density, circulation, and marine life distribution. Variations in salinity result from processes like evaporation, precipitation, river inflow, and ice formation or melting. Ocean chemistry encompasses the study of all dissolved substances, including nutrients and gases, which together regulate Earth's climate, support ecosystems, and drive biogeochemical cycles in the oceans and seas.
💡 Key Takeaways
- Understand what ocean salinity is and how it's measured (PSU/Practical Salinity Units and CTD sensors)
- Learn how salinity affects seawater density and drives ocean circulation and vertical mixing
- Identify the main sources and sinks of salt in the ocean (evaporation, precipitation, river inflow, sea-ice processes)
- Explore how salinity interacts with carbonate chemistry and pH, and what that means for marine life
❓ Frequently Asked Questions
What is ocean salinity and what units are used?
Salinity is the amount of dissolved salts in seawater. It’s usually reported in practical salinity units (PSU) or parts per thousand (ppt). In the open ocean, 35 PSU ≈ 35 ppt.
How do salinity and temperature affect ocean chemistry and density?
Higher salinity and lower temperatures make seawater denser, influencing circulation. Salinity also affects how much gas (like CO2) the water can hold—the saltier the water, the less gas it can dissolve.
What is the ocean carbonate system and why is pH important?
The carbonate system includes CO2, carbonic acid, bicarbonate, and carbonate ions. It acts as a buffer, keeping seawater around pH ~8.1. Adding CO2 lowers pH (ocean acidification) and removal raises it.
What processes change seawater salinity?
Evaporation raises salinity, while precipitation and river inputs dilute it. Sea ice formation leaves salt behind in surrounding water, increasing local salinity; mixing distributes salinity across the ocean.