The day is overcast and sleety. Winds are at 40 knots, gusting to 50 and snow whips across the bridge windows. The ship is hove to, riding out the weather and the decks have been closed since 0900.
Post party it’s a quiet morning. I have a lesson in marine geology. There’s a revolution going on in this field. We now have the tools to map the entire seafloor in the way that Geographic Information Systems have mapped the land.
This is Dr Rob Beaman’s area. To show why this matters, he constructs a computer map of Voyage 3’s ocean section. Prior to the voyage he gathered data to construct maps of the ocean around Antarctica. Tables of geographic information, such as latitude, longitude and depths from the GEBCO (General Bathymetric Chart of the Ocean), were created using ship’s soundings. Rob uses this data to create a 3-dimensional ocean surface.
However ships do not go everywhere in the world’s oceans. Gaps in the information come from another repository of data called ETOPO2, which uses satellite radar to reflect changes in the topography of the deep ocean. Rob colours the sea floor according to depth. The shallow bits are red deepening to purple. Then he adds a ‘sunshade’ and we are in 3D and able to see shadows and valleys from any chosen direction.
In front of me, a map shows the detailed ocean floor between Hobart and Antarctica. This is the Gondwana story. I can see where Tasmania was once linked to the Antarctic mainland. The underwater volcanos, also known as seamounts, are clearly visible in the 3D map. An undersea plateau, the Tasman Rise, emerges from the deep abyss. On the Antarctic continental shelf are dark purple lines indicating the massive scours that followed the movement of the glacier during the last ice-age. The mighty Mertz glacier could only go west because of the shape of the George V Basin and those ‘mega flutes’ or deep gouges are evidence of its path.
The final addition to our map comes from the latest multi-beam sonar technology. Carried beneath a ship, it creates a picture of the seafloor in a swathe many kilometers wide. Rob has some images from a previous trip and these strips further reveal the criss cross of icebergs drifting over the seabed. It’s these areas that will show marine biologists how life recovers in this iceberg-disturbed environment. If you can find the scours you’ll find the places where life concentrates, on the ridge tops and outside of the scours.
If multi-beam scans were used to complete the undersea picture covering our grid of stations, imagine how precisely and selectively the biologists could target the seabed features that could tell them the most about life on the sea floor.
I take a turn on the bridge. We have been stooging for hours between stations 59 and 60, running north and south with the swell, waiting for conditions to improve.
Captain Moodie checks the weather forecast using data downloaded from GRIB. There is a series of big lows coming from the west. The winds are consistently high and it may not be possible to open the trawl deck for several days.
I ponder what a voyage would have been like without computers.
Pic: Rob’s Gondwana map
Margot Foster is a journalist currently on board the Australian Aurora Australis, an Australian research vessel currently participating in the Census of Antarctic Marine Life (CAML, IPY project 53). She works with the Australian Broadcasting Corporation (ABC).