Cape Reinga, at the very northern tip
of New Zealand's North Island, is one of the few places in the world where
you can watch two oceans collide. So say the guidebooks, anyway.
The truth is a little more complicated. First of all, you can find photos online
like this. I took that from a kayak in Svalbard,
up in the Arctic. Two very different coloured waters separated
by a bit of foam. People online claim that photos like it show
one of the few places in the world where two oceans meet but don't mix,
but no. That's just where a river is washing fresh water
filled with sediment out into the sea. The truth of where two oceans meet is just
not that dramatic. Here, at least, you can see the waves from
the Tasman Sea coming in from the west and clashing with the Pacific Ocean
waves from the east. Right? No. Ocean currents and waves have many causes: the weather, water temperature,
water salinity -- how much salt’s in there. And they’re three-dimensional. Now, with all the complicated geography and wind
here at the very tip of the country: of course it’s chaotic down there,
it's turbulent, of course you have different sets of waves
meeting, but those are local effects. As soon as you get away from land, the water here will become part of the massive
system that's defined by global weather and ocean currents. And those ocean currents are
measured in sverdrup. One sverdrup is a million cubic metres of
water, moving at a metre per second, and the largest currents measure more than
a hundred sverdrup. Those are amounts that make no sense
on any human scale. While there are often currents here that might
contribute to that particular weird wave pattern... this is just one very, very small bit of the ocean
with waves that look messy on a human scale because of the land nearby. And despite what the guidebooks say, this isn't even where the Tasman Sea ends
and the Pacific begins. Not according to the maps. The official limits of oceans and seas are
defined by the International
Hydrographic Organisation, and those standards are arbitrary lines designed
to make sure that everyone can agree on what’s where, so that weather warnings and marine charts describe
the same areas no matter who's producing them. Those lines are nothing to do with the position
of any ocean currents. And according to those standards, the Tasman Sea meets the Pacific
at North Cape, a closed nature reserve
about two kilometres that way. This is just a windy bit of rock
with a lighthouse and a road. That doesn’t mean you shouldn’t come here, though. Cape Reinga is beautiful, it’s part of the local mythology,
and it’s worth the trip. But when they say it’s where two oceans
collide… that just isn’t quite true.
TIL the word "sverdrup."
There is only one ocean. It's the continents and islands that are separated.