This week at Davis: 24 February 2017
This week at Davis we're wrapping up science projects and the ship has arrived.
Tracking elephant seals in the Southern Indian Ocean
The elephant seals have started arriving in the Vestfold Hills for their annual moult. Southern elephant seals breed and moult on a number of sub-Antarctic islands. However, there are instances where seals have bred in the high Antarctic, for example on Petersen Island, or in temperate regions like on King Island in Bass Strait and even in Western Australia.
After the breeding season, moulting commences when seals return to land. Moulting generally occurs on the breeding islands in the sub-Antarctic, but also in the Antarctic e.g. the Vestfold Hills. The elephant seal moult is dramatic and the seals shed both their hair and the first layer of skin. This process takes between 30 days for younger seals and up to around 55 days for older sub–adult males. It is at the end of the moult that we attach our state–of–the–art oceanographic trackers to the seals.
These trackers don’t only provide information on seal movement but collect information of ocean conductivity i.e. ocean salinity, ocean temperature and depth. Conductivity, temperature and depth or CTD information are the essential observations needed to quantify ocean structure and hence state of the ocean.
Because the seals can dive to great depths – up to 2100 metres, they are collecting data on water column structure that is important for understanding how Antarctic bottom water is formed. Understanding how and where this bottom water is formed is important for interpreting global heat and oxygen mixing rates.
Despite the importance of the Southern Ocean little is known about its physical structure, especially South of 60° where conventional sampling using ships and ARGO floats is, at best, sparse. Attaching high resolution oceanographic sensors to animals is resolving the paucity of data from South of 60°. Importantly, animal tracking data can provide valuable insights by collecting data over a number of years from predictable migratory routes across vast swathes of the Southern Ocean.
Individual animal-borne CTDs allow us to record physical properties of the ocean and to quantify those attributes in areas of ecological importance to animals. The Integrated Marine Observing System (IMOS) is supporting tracking of several species in the Southern Ocean using CTD tags and has so far provided more than 90 000 CTD profiles in the Southern Indian Ocean. The Davis team of seal researchers (Clive, Esther and Fernando) are building on this incredible time series of 13 years of observations and have so far this summer deployed five of the CTD tags on male elephant seals at Davis station which complements deployments at Iles Kerguelen in a sister project also supported in part by IMOS.
Our work tracking seals, where we integrate in situ physical attributes of the environment with animal performance are helping us get a much better handle on how the environment influences individual animal performance, population structure and persistence and ultimately ecosystems' structure.
As with any study, success depends on a lot of people and organisations and we would like to thank: the Australian Antarctic Division for supporting our work here at Davis, IMOS for supporting long–term and incredible time series of unique ocean observations, all of the wonderful folks at Davis station that have made us very welcome on base and been helpful at every opportunity and of course all of our families and friends back home for supporting our Antarctic adventures.
Clive (Seal Researcher)
Hydrographical surveys at Davis
The end of the boating season is fast approaching at Davis in what has been a successful season which began on the 9th of January 2017 for both Geoscience Australia (GA) (in the Division's workboat Howard Burton) and the Royal Australian Navy (RAN) (in the Antarctic survey vessel (ASV) Wyatt Earp). A total of 34 days of sounding has been accomplished so far, which encompasses the mapping of large areas offshore and to the north and south (112 km2) which address both charting and scientific objectives, collection of 20 seabed samples, camera drops and 33 line km of sub-bottom profiles.
For those not familiar with Project 5093, it is a collaboration between the RAN, GA and the Australian Antarctic Division with the information we collect being used for safety of navigation in Antarctic waters and to support a range of scientific, environmental management and operational activities. In gathering this information we use a variety of equipment, including multi–beam echo sounders, sediment grabs, sub-bottom profilers and underwater cameras.
A typical day for the team begins at 0730 with the boats being lowered into the water by crane – an operation which took a bit of patience and ingenuity by personnel from both boats and the Division's plant operators.
The boats then transit to their particular survey area for the days soundings or sampling, which may include one or more of the aforementioned equipment with the aim to be back alongside Davis wharf by 1700 for recovery and processing of the data.
What do we mean when we say sounding an area? The multi-beam echo sounder is our primary sensor used to measure depth, collect backscatter and water column data. We do this by driving the boat in “lines”, (also called mowing the lawn) to ensure that we achieve 100% coverage of a particular area. Once the area is completed we move onto the next. Some areas are larger than others and while some lines may only be a minute or two long, some are much longer and depending on wind, sea ice and sea state can be tricky to drive.
No matter the weather conditions for the day – overcast or clear – the scenery supplied by Antarctica out on the water is spectacular. Icebergs from small to very large in all different shapes and sizes with the most amazing colours provide much viewing pleasure and plenty of photo opportunities for team members and a few lucky personnel who have had the opportunity to come and spend a day out assisting us on the water.
There have also been times when those magnificent bergs are just sitting in the wrong spot – right where we need to drive the boat. Some of those bergs have moved along and we have been able to revisit areas and fill in the gaps left. Others will have to wait until the next hydrographic surveying teams visit Davis.
Although spectacular, there have been instances where the dangers of working in Antarctica have been reminded to us. We have witnessed icebergs roll over and break apart. There have also been times where we have had to return to station at the rush due to deteriorating weather conditions and sea ice floes threatening to make the wharf inaccessible.
There has also been plenty of wildlife to keep us entertained. From the endless supply of penguins to killer whales and seals. ASV Wyatt Earp was lucky enough to have a whale surface right next to her and we did see a pod with numbers around 12 swim by us while eating lunch, which along with the backdrop was extraordinary and something most people only get to see on a David Attenborough special.
Both vessels have had curious penguins join them on the back deck, just to make sure we were alert and doing our job properly. Luckily they decided against joining us in the cabin. We have all seen the elephant seals which like to block the road to the wharf, or play alongside it in the water with the occasional Weddell.
Boy, have there been plenty of ups and downs in the boats (puns intended), but the experience is one that not one of us will forget in a hurry. It is definitely a privilege to just come down here, but having the opportunity to work out on the water in this environment makes us some of the luckiest people.
Cooksey (Watercraft Operator)
Sunsets and sun dogs
It is the time of the year at Davis where we are seeing the sunset and sunrise. This is because they are occurring at a reasonable hour. Lately we have been seeing some spectacular and vivid colours from around 10 pm and also in the morning around 6 am.
The reason for the amazing colours are as follows: As the sun sinks toward the horizon, sunlight enters the atmosphere at a much lower angle and consequently must pass through much more atmosphere before being seen by an observer. Air molecules scatter away the shorter wavelengths of light (violet and blue) and the only light which penetrates through the atmosphere are the longer wavelengths of light (yellow, orange and red) which produce colourful sunsets.
During many of the late evenings this week we have seen intrepid photographers wandering out and capturing beautiful images. The downside is the very cold hands. Before one of the sunsets we witnessed 'sun dogs'. This phenomena is caused by light interacting with ice crystals in the atmosphere. Sun dogs typically appear as two subtly coloured patches of light to the left and right of the sun, approximately 22° distant and at the same elevation above the horizon as the sun.
Barry (Met Observer)
The ship arrives
Well the ship is finally here, sitting out in Prydz Bay, nestled amongst the icebergs.
Meanwhile on station we’re finishing off our preparations. Oh yes, and had a night of celebration to mark the end of the season. Tomorrow it all begins: cargo arrives, RTA (return to Australia) cargo goes, and some of our expeditioners head out to embark the vessel. Additionally, there is mail and fresh fruit. Not that we are lacking for anything here on station, but physical mail is exciting, even in this day and age.
Once the cargo movements have taken place, more expeditioners will join the ship. We’re not quite sure how long the ship will be here, but for now it’s very operations focused. Saying goodbye to people and Davis will be difficult… plenty of time yet for that.