Hi, this is Kate from MinuteEarth. Earth’s ocean water, all 140 million-ish
square miles of it, is all interconnected - which becomes really clear when you look
at the world like this. Technically our planet only has one ocean:
the giant, not-so-creatively named “world ocean.” But that makes it hard to talk about different
parts of the ocean on different parts of the planet. It makes sense to split it up, but how do
you divide a continuous body of water? Since we humans have a habit of making things
all about us, historically we have divvied up all that water based on our own perceptions. For example, centuries ago, western seafaring
routes clustered in certain areas, like between Europe and North America, and western Africa
and South America; as a result, we thought about these areas as separate “oceans.” But the problem with dividing up water based
on our worldview is that our worldview is...well...fluid. As our routes diversified and our horizons
widened, we began to recognize just a single Atlantic. The same thing happened elsewhere in the world,
and we ended up with four big, blobby oceans outlined mostly by land. To deal with parts that aren’t outlined
by land, we - well, specifically map-makers and government organizations, who like things
cut-and-dried - took the sticky-outy-est bits of land and extended lines straight out from
them. Boom, problem solved; we now have clearly
defined oceans! But here’s the thing: the bit of water at
the very edge of, say, the Indian Ocean is no different than the bit of the Pacific Ocean
just next to it; in fact, those two bits of water are more similar to each other than
they are to other bits of water in their respective oceans. So, while these boundaries may be clear and
convenient, they don’t really say much of anything about the oceans themselves, which
seems kind of important. Maybe we should use what we actually know
about oceans to divide them. If we look at, say, their saltiness, or the
currents that drive the top layers of water, ye olde division into two Atlantics actually
makes sense. But if we consider geology, underwater ridges
actually cleave the Atlantic into east and west. And sea surface temperatures suggest we throw
out the continents as boundaries altogether. So, even science doesn’t seem to have a
clear answer on ocean-divvying, except in one case: the water surrounding Antarctica. Ringed by a strong, east-flowing current and
a convergence zone where frigid polar water collides with warmer, saltier water from the
north, the so-called Southern Ocean is different in pretty much every way from the water that
is essentially right next to it. And while it isn’t officially deemed an
ocean by the world’s ocean-deeming body, it seems like the only bit of the “world
ocean” that we can actually justify separating out...all those other divisions just don’t
seem to hold water. Ok, so dividing up the oceans in a way that's
both intuitive and helpful is clearly kind of a problem. Problems like this can be complex and daunting,
so where do we even start? If you'd like to learn how to tackle complex
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