To simulate interactions between the Southern Ocean and the
Antarctic ice sheet. We separate the ocean into
hundreds of millions of chunks. A special coordinate system
accurately represents the terrain of the sea floor.
Using one of the fastest supercomputers on Earth provided
by the National Compute Infrastructure at the Australian
National University. We then calculate the exchange
of momentum, salinity and temperature between these chunks.
Somewhat magically, larger circulation features such as meanders
and eddies appear and act to transport and diffuse heat and salinity.
The ocean forms internal layers which we can visualise using
surfaces of constant salinity. High salinities are found near the
sea floor, while the lowest salinity corresponds to the ocean surface.
Here we colour the constant salinity isosurface with a temperature scale
to show the thermal gradients. We also removed the surface,
which is far from the coastline, for clarity.
Some of the deeper layers feature the highest temperatures, and this deep,
warm water is known to be a great threat for the adjacent glaciers.
To simulate the effects of this deep, warm water among other water masses
our model resolves melting underneath the floating parts of
the ice streams, the ice shelves. The glaciers of East Antarctica are
of particular importance, as they hold more sea level rise potential
than any other region on Earth. Here, large parts are grounded below
sea level, and intrusions of deep, warm water could trigger a rapid
runaway retreat.
Ocean tides are also an important process.
They circulate the continent as large waves and modulate ice
shelf melting in many ways. For example, tidal currents directly
modulate melt rates by supporting the exchange of heat and salinity
right next to the ice.
More indirectly, tidal waves inside the ocean can lift deep,
warm water onto the shelf break, and thus closer to the coast.
Some of the strongest tides around Antarctica exist near the
Filchner–Ronne Ice Shelf. The meltwater generated here
plays a special role, as it is involved in the formation of
a very dense and cold water mass. Ultimately, this water leaves the
continental shelf and spreads as Antarctic bottom water along the
seafloor of the global oceans.
Interactions between the Southern Ocean and the Antarctic ice sheet
impact global sea levels and climate. Realistic simulations like this
can help us to better understand the involved processes and improve
predictions of future change.