When I say the word “weather” what comes to mind?

Maybe some light rain, a thunderstorm, a tornado, a blizzard. There are a lot of different weather phenomena in our atmosphere.

But have you ever thought about the possibility mof weather in our oceans? Some of the same causes of atmospheric weather exist in the ocean, too. And it can impact marine wildlife just like a storm affects us.

So let’s take a look at the weather underwater! [Intro music] If you’ve ever listened to a weather report, you’ve probably heard the word “front” being thrown around. The meteorologist is talking about air masses that differ in temperature, wind, and humidity. And in the ocean, fronts are pretty similar.

Thats where water masses of different properties meet. Instead of differences in temperature, wind, and humidity, you've got differences in temperature, salinity, density, and more. Ocean fronts also move around as ocean currents and winds interact with them.

So, just like meteorologists track the movements of these boundaries in the atmosphere, oceanographers are working to improve how we track them in the ocean. And ocean fronts can be really important to marine wildlife! Let’s start with plankton: The gradients of temperature, salinity, and other water properties, reduces the amount of mixing  at these frontal zones.

With limited mixing, phytoplankton aren’t carried to deeper water, allowing them to stay in the brightly lit surface waters and providing them with the opportunity to photosynthesize. Phytoplankton are the base of the food web. So if there’s an increase in phytoplankton, it will start to attract larger lifeforms.

Zooplankton eat the phytoplankton, fish eat the zooplankton, and so on. For example, seabirds are frequently found at the borders of ocean fronts. Especially king penguins and albatrosses.

And so are filter feeding basking sharks! In some areas, they seem to  follow the fronts as they shift, probably taking advantage of elevated levels of zooplankton! They have to follow the food, stalk the snacks, pursue the provisions… you get the idea!

So you can see why marine scientists like me care about ocean fronts. They give us a lot more information than just if we’ll need an umbrella that day. Eddies are another type of weather underwater, but they’re a bit different than eddies in the atmosphere.

Those are essentially whirls of air. Rather than the air moving in a straight streamlined way, it moves in a more turbulent, circular motion. They’re often caused by an obstruction of a smoother airflow by something like a building or mountain.

Some aeronautic courses even explicitly mention these eddies because they can cause turbulence, especially for smaller aircrafts and drones. In the ocean, they're on a much larger scale, like 10-100km in diameter! And they can persist for months.

While you can have smaller eddies that create turbulent flow of water like the atmospheric eddies I mentioned, these eddies are created when they break off of a larger ocean current. For this reason, they’re a  bit like atmospheric storms. They trap water from one water mass inside a different water mass with different properties like temperature and salinity.

And there are a few different types Cold core rings are essentially when cold water gets trapped in warmer water. They produce an upwelling effect, drawing nutrients up from deeper water towards the surface. This is perfect for photosynthesis And photosynthesis is dope, Hello phytoplankton productivity!

Warm core rings are the opposite. This is where warmer water is getting trapped in cooler water, and they produce a downwelling effect. This shunts warmer surface  waters into the cold depth.

It’s almost like a portal for  deep diving animals like sharks that allows them to stay deeper for longer by releasing them from thermal constraints they experience while diving. Which is a pretty cool trick for a swirl of water! This SciShow video is supported by Arizona State University’s  College of Global Futures.

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With ASU, the world is your oyster, especially if oysters mean the world to you. OK, we’ve finally reached what is in my opinion the most confusing of our 3 underwater weather systems: gravity waves! Not to be confused with gravitational waves.

Gravity waves are called this because gravity is the restoring force here that is essentially working to flatten the waves back down into a flat plane. In our atmosphere, you may have seen them in the form of weird clouds that look like ripples in a pond. And that is essentially what they are!

But instead of throwing a stone into water, it's an updraft of air that disturbs an otherwise stable air mass to create such an effect in the sky. It’s similar in the ocean, but rather than a ripple on the top, it’s an internal wave. A wave beneath the ocean’s surface.

Instead of the wave happening at the interface of water and air at the surface like you’d see on a beach, it’s a wave that moves along the boundary of two water masses that are separated because of their differences in density or temperature. A water and water interface. These internal waves can be  caused by a lot of things, but really anything that  would cause the displacement of water can create them.

A great example is the movement of the mixed layer based on the winds. What is the mixed layer? It’s the surface layer of the ocean where you see lots of mixing due to heat flux, salinity, and other properties.

The stronger the winds, the more mixing there will be, and the deeper the mixed layer will be. This deepening or shallowing of the mixed layer causes displacement of water at that water and water interface I mentioned. Now you’ve got a wave propagating along that boundary, an internal wave!

And like the other underwater weather we’ve talked about, large internal waves have  an important part to play in sustaining ocean life. They may dampen the effect  of heat stress on corals! When corals get too stressed  from the high temperature, they expel from their body the algae that helps them make food.

Without them, the coral can die. This is called coral bleaching, and it’s devastating to our reefs. But one study shows that large internal waves may bring in cooler waters and additional nutrients and plankton that the corals can use for food.

Limiting the severity of these bleaching events. A site that was cut off from  the effects of internal waves experienced more bleaching than a site that did experience them. So even if they’re a little hard to understand, gravity waves can be lifesavers.

And these are just a few  examples of ocean weather. There are even more physical processes down there that affect wildlife. We have some pretty interesting  weather phenomena up here, but so do our ocean dwelling friends!

I wonder if fish ever make awkward small talk about the weather, too? [ OUTRO ]