I very recently spent time in the tropics (nice place) and enjoyed the beautiful, clear, blue green waters of the Pacific Ocean. I’ve also (who hasn’t) seen those photos of beautiful, clear, blue green waters on any given tropical place that is looking to attract tourists. Sadly, I live near the not so beautiful, murky, gray green waters of the North Atlantic. (did I mention COLD?) So here’s my question: What causes tropical seas to be clear and beautiful and makes cold waters murky? Why does the sand from the beaches in cold climates stay suspended in the water and drop like well, sand, to the bottom in warm waters? What else is in there that makes it murky (even away from shore)? Why doesn’t the cold ocean ever have that lovely blue/green color even on sunny clear days? Heck, even the seafoam here is grundgy looking, not white and bright like in the tropics.
OK, I want to go BACK! NOW!
IIRC it’s a combination of algae / plankton growing in the waters, coupled with (believe it or not) the reflection of the blue sky in the water.
Hope that helps…
Different currents and conditions bring in or stir up more silt as well.
The numbers and types of rivers that dump into the area contribute to conditions.
Different sands have different reflective properties that highlight and reflect colors.
In some areas off the Northeast USA, you can see down about 10 feet - not as great as say the Carribean, but better than most people would expect.
Colder waters are more fertile, with more of the biomass in suspension. In tropical waters the main phytoplankters are symbiotic with the reef building organisms and thus not floating around where they can be eaten by the first feather worm they come across.
The soil in tropical areas is usually thin and poor in nutrients while the soil in temperate and colder waters has a lot of organic material. The organic portions (technically known as “mud”) take longer to settle out of water than the almost sterile sands of a tropical beach resort.
Tropical waters may have more colourful fishes, but compared to the amount of life a temperate or colder sea can support the areas away from the reefs themselves are deserts. I remember reading somewhere that the cod harvest alone for a few years in the early 70s surpassed the estimated biomass for the entire Great Barrier Reef.
Your tropical waters look prettier because they are not infested with life.
Begg’in your pardon Doc - but I thought the main difference was the proportion of diatoms to salinity percentage in the water? It’s higher in Northern colder regions thus , more diatomic growth.