Of Antarctica’s sea ice
rises towards the surface, it finds ice crystals to solidify onto and becomes a platelet.
These become more buoyant and eventually join the platelet layer.
In winter, the layer helps sea ice form. In spring and summer, it seems to insulate sea ice from melting from below, at least for a time.
In other words, platelet ice is thought to be one reason sea ice around Antarctica isn’t melting as much as the climate change models suggest.
And it follows that the lack of platelet ice in the Arctic may partially explain why sea ice melt up north is more serious.
Robinson, colleagues and students want to know how far these effects are felt. ‘‘We’re looking at how the ocean responds to having that platelet ice there,’’ says Robinson.
‘‘The question we’re trying to answer is how far away from the ice shelf that influence extends ... it might be a local one or might it extend a few hundred kilometres.’’
‘‘Based on the data we’ve collected so far, we’re comfortable it extends at least 200km.’’ At that point, it gets confused with the water coming from other sources.
But this is where Robinson’s platelets meets Langhorne’s scaling up.
With some maths, the gadgets flying under the DC3 can measure the platelet layer. This is new.
‘‘There are little ice shelves all the way up the coast, where nobody has ever looked for platelet ice,’’ says Langhorne.
They hope to fly the gadgets over new areas of the Ross Sea. ‘‘There might be something to see. There might not,’’ she says.
If these teams can measure the platelet layer from the air and sea ice from space, then a much fuller understanding of the Ross Sea will be possible.
It’s the baseline, remember, the coast least affected by global warming. Elsewhere along the Antarctic coast, ice shelves are melting at an alarming rate.
‘‘At the moment, we can say that water flowing through McMurdo Sound from the Ross Ice Shelf probably hasn’t changed much in at least 200 years,’’ says Robinson.
‘‘It’s a good place to understand the processes as they happen because they are pretty stable.’’
And then scientists can learn more about ice systems that aren’t stable, that have changed.
And the knowledge can be plugged into climate change models to get better predictions of how long we’ve got.
‘‘We go every year and we find out new things each time,’’ says Robinson. ‘‘This really is a place that science is still exploring. We are literally pushing frontiers with our science with every field season.’’
❚ Will Harvie and Iain McGregor spent 10 days in Antarctica as part of Antarctica New Zealand’s community engagement programme, which allows New Zealand media, artists and other non-scientists to visit Scott Base to learn and report on the work of scientists on the ice.
‘‘We go every year and we find out new things each time. This really is a place that science is still exploring.’’
Dr Natalie Robinson
- amarine physicist at Niwa