Sailing in the Great Southern Ocean (1): ice gates and satellite detection systems

Sailing across the Southern Ocean is one of the most thrilling chapters in any round the world regatta. During the latest IMOCA Class events such as the Vendée Globe and the Barcelona World Race, “ice gates” have been the focus of much attention with brand new satellite detection technology being made available to the organisers revealing the dangerous icebergs, growlers and bergy bits putting the skippers taking part at risk. In this first article on the subject, we look at the advantages and disadvantages posed by the gates and the level of guarantee provided by detection systems in terms of exact location of ice. On February 5th 2013 the subject will be debated at a round-table discussion to be streamed on the web with Joan Vila, Marcel Van Triest and Jorge Luis Valdés.

Articles JAN 18, 2013 01:00

“Ice gates”, as they are known, are in fact imaginary lines which run along a fixed latitude set between two longitudinal coordinates, usually some 350 miles in length. In the editions of the Vendée Globe 2008/09 and the Barcelona World Race 2010/11, as well as in the current edition of the Vendée Globe 2012/13, the Race Directors chose to position the gates along the Southern Ocean stretch of the course, with the skippers required to cross them by putting one of the two points south. The main aim is to limit the boats' descent into dangerous waters where an abundance of icebergs and growlers might be found.

Las puertas de hielo son segmentos de latitud

When circumnavigating the Antarctic the further south one goes, the shorter the course as one draws closer to the Great Circle route which would be traceable along the polar ice cap. The very first round the world regattas such as the Golden Globe, the Whitbread, the BOC or the Vendée Globe, offered no restrictions other than putting the Capes of Good Hope (South Africa), Leeuwin (Australia) and Horn (Chile) to port, and in doing so gave the skippers total freedom to plot their weather strategy. That involved placing oneself in the best possible position within the northern sector of the squalls in order to enjoy the fair winds, otherwise known down at these latitudes as the “Roaring Forties” or the “Furious Fifties” and also trying to avoid becoming caught in transitional zones where the breeze may drop suddenly and force boats to grapple with hellish seas. 

Many of the images imprinted in our memories of these first southern passages involve icebergs and icicle-covered decks with skippers manoeuvring through howling gales. Right now, only the yachts taking on the Jules Verne Trophy have total freedom to choose their routing along the icy stretches of the southern seas. However, skippers apply common sense in abundance, as could be seen with Thomas Coville on Sodebo and Loïck Peyron on Banque Populaire: both went around the zones where ice posed a particularly high risk, despite it costing them valuable hours in their race against the clock. 

Ice gates came about due to the round the world race organisers' increasing concern for the safety of participants. More and more information about the location of dangerous ice in the Southern Ocean has become available to them thanks to satellite detection services. The Vendée Globe 2008 organisers hired French company CLS and for the Barcelona World Race 2010 the FNOB chose to employ the services of Canadian firm C-Core in order to detect the dangerous ice. The results of these studies caused widespread concern: boats had been sailing blindly through the Great Southern Ocean across areas where ice was far more abundant than had previously been thought.  

A question of sport: changes to strategy and mode of sailing 

Ice gates have been controversial since they were introduced. Mainly because they have been moving further and further north and are the source of numerous modifications to Racing Instructions. In the Vendée Globe 2008/09 the change in position of the gates added 572 miles to the theoretical course (it went from 24,016 nautical miles to 24,588 nautical miles) with some gates moved some 320 and even 480 miles further north. The Barcelona World Race 2010/11 also introduced considerable modifications to almost all of the gate positions, with Gough Island added as the first entry was still making its way along the west of the St Helena high. The ice gates for the current Vendée Globe were changed before the first entry had reached the Pacific.

Las puertas de hielo inicialmente establecidas en la Barcelona World Race 2010/11

These changes stirred up some adverse reactions among the entrants. To start with, the organisers had increased the theoretical course by lengthening the orthodromic route which sparked some complaints from skippers regarding their calculations of provisions for the race. However, the main objections were about changes to navigation mode: the gates changed the boats' initial strategy in terms of the squalls in the Southern Ocean and forced them to sail in unusual conditions for the area, with more upwind sailing and sudden storms due to their proximity to warmer waters and the Indian and South Pacific high pressure systems. There have been similar reactions in the current Vendée Globe. However, for François Gabart the gates are a tactical challenge: “I don't think that the ice gates take away from the tactical and strategic interest of a round the world race, but the opposite. They provide more points of reference and more gybes and tacks which must be executed with more precision. Of course these races cannot be compared with the round the world races of old”. 

Overall there is a general consensus of acceptance of the gates, as they do offer a significant increase in safety for the entrants. Marc Guillemot explained this in the following terms ahead of the start of the most recent Vendée Globe: “I think the ice gates are essential, as their main function is to help us to finish the race. Seeing icebergs is a beautiful thing, but... What matters is that new technology can now offer the most exact coordinates so that the gates may be positioned in the most suitable locations so as not to affect the strategic challenge of the regatta”. 

Satellite detection technology

Satellite detection is key in locating the presence of ice and in terms of reliability in predicting where the ice may drift. This is a fascinating field with a plethora of applications beyond its use in the world of sport and is a practice which can be carried out with high levels of precision, although its implementation in the context of a regatta can be complicated.

Cada iceberg se identifica mediante un punto verde

It is well-known that large icebergs pose a relative risk, as they are detectable using on-board radar systems and are visible during the day, if there are no adverse or foggy weather conditions. The biggest risk is posed by growlers, which are smaller pieces of floating ice, undetectable by radar and very difficult to make out by simply looking out for them amid the usually rough seas of the Southern Ocean, often only protruding by approximately one metre or so from the water. The presence of growlers is directly connected to that of icebergs, as they are generally formed when parts of an iceberg break off as it heads into warmer waters.  

The only way to detect ice in the sea on a large scale is via satellite. There are currently two means of satellite detection in existence: a system which analyses radar imaging and satellite altimetry. The radar imaging system, which up until now was the traditional system in use, employs extremely powerful long range radar which permit observation of the sea's surface in sections of 400 x 400 km with a 150 metre resolution. These images are taken at a rhythm of 30 minutes and are usable at 100 minutes. Depending on the sea state, for example if there are big waves, the images obtained on the basis of the reflectivity registered in the return signal to the radar tend to suffer from “noise” and must undergo a special procedure before ice can be detected. Images obtained in this way must be taken some three days in advance.  

The second system, based on radar altimetry, measures variations in sea level and has a scope of just some five kilometres, which perhaps might

Iceberg de unos 100 metros de longitud

appear to provide fewer possibilities to map the ice across large areas of the sea, however it boasts the great advantage over the imaging system of working continuously with three satellites which allows a mesh of data of a more than acceptable density to be created. The precision of the system in terms of height is to within a few centimetres so that if an object pokes through the water surface by even just a few tenths of a metre it would, in theory, be detectable, providing that the height of the waves didn't distort the image.

The first time that radar altimetry was used in ocean sailing was during Franck Cammas' 2009 challenge when he took on the Jules Verne Trophy with Groupama 3. For the current Vendée Globe a combination of both systems, imaging and altimetry have been used to achieve the best possible results. Continuous altimetric observation detects, for example, a concentration of signals which may make up a concentration of ice, which in turn spurs the use of radar imaging on the area in question in order to verify the level of danger and if it is, in fact ice or perhaps a vessel.  

Once ice has been positively detected, programmes designed to predict its drift launch into action. These programmes are based on models incorporating some basic variables such as current, wind, swell and sea temperature and are fairly precise. For the Vendée Globe, CLS is responsible for this. The level of reliability of these systems was made patent in the Vendée Globe 2008 when they managed to identify and predict the drift of a large iceberg which crossed Sam Davies' course on Roxy near to the Kerguelen Islands. The British skipper got to within half a mile of the mass of ice and managed to take a photograph (see photo 1). 

A problem with using both imaging and altimetry systems combined is the cost. The demand for imaging is far greater in the northern hemisphere than in the southern hemisphere, with the price shooting up as a consequence in that part of the globe. Future evolution will be based on looking at the cost-effectiveness of the technology and will see developments in the software to predict drift, advances which can be applied broadly across the fields of oceanography and maritime safety. 

Safety levels. How real is the danger? 

What level of safety do these detections offer? Are gates the best system for preventing the danger posed by the ice? These are the key questions being debated in discussion on the future of round the world regatta routing. From a safety point of view, gates are better than the four waypoints set out in the Vendée Globe 2000/01 as they allow organisers to offer safer margins and give skippers more tactical options. However, it is clear that they still don't offer a totally effective guarantee against the danger of floating ice.

El famoso iceberg B-15 y sus millares de fragmentos

Firstly, it is not easy to track a theoretical course with gates some two months in advance; it is an extremely complex task, as the drift of the ice means that it is on the move constantly. Also, the Race Directors can only change the position of a gate if no entry has already crossed the gate previous to it. This forces them to plan ahead for the first South Atlantic gate, which in both the previous Barcelona World Race and the current Vendée Globe was not a gate, but Gough Island, and it means that it must be done far ahead enough that it can't be changed, either benefitting or not the strategy of the leader. Once an entry crosses one of the gates it can't be modified, in order to create a level playing field for the entire fleet. That might be enough in the Atlantic but in the Pacific, when the leaders have already rounded Cape Horn, there may be difference of almost one month between the tail end and the top of the fleet, and that's more than enough time for the ice to have drifted significantly. That can be even more dangerous in the Barcelona World Race when the tail end may reach the area surrounding the legendary cape at the beginning of the southern autumn.  

What is the reality of the problem? It has been proven that ice may lurk and has been detected in relatively warm waters, at a temperature of 8-9 ºC above 45º S, as could be seen in the C-Core study carried out during the month of December, a few days ahead of the start of the Barcelona World Race. Contrary to what most skippers might believe, waters at above 8 ºC may also carry ice, and of the worst kind: the feared growlers which are formed when larger icebergs begin to melt and pieces break off, and icebergs now being found in warmer waters due to climate change in the Antarctic which are enormous and have a very long lifespan in these waters: in 8 ºC waters, an iceberg loses a metre a day of its entire perimeter and in waters of 3-4 ºC, usually found below 50 ºS the rate of daily shrinkage is at around 15 cm. 

However, respecting the gates doesn't mean that the boats don't enter dangerous waters. In the current Vendée Globe, Alex Thomson made his way down to 45ºS between gates Agulhas and Crozet, getting as far as the 'official' limits of the sea ice. Is there a need to develop a “forbidden zone” in the Pacific, as in the Volvo Ocean Race? Does more money need to be invested in satellite detection? Does specialist onboard technology need to be developed for the yachts themselves? On the 5th of February at the Barcelona World Race Interpretation Centre in the Spanish city, navigator Joan Vila, meteorologist and router Marcel Van Triest and UNESCO scientist Jorge Luis Valdés will be debating the issue. The round-table will be streamed live on this website with simultaneous translation in French and English. 

Our next article in the series on the Great Southern Ocean will include an interview with Joan Vila, the sailor currently holding the Jules Verne Trophy after taking it on Banque Populaire with Loïck Peyron, and will also take a closer look at the issue of collisions with ice and UFOs, as well as the strategy applied by skippers in these situations and the technological options available for detection.

Santi Serrat