Antarctic icebergs a source of freshwater

As the world’s population increases over the next 50 years, demand for water will increase dramatically: by 2030 global water demand will outstrip supply by 40%. With 90% of the 3 billion people expected to be added to the world’s population by 2050 living in developing countries there will be additional stress placed on water supplies, particularly in regions where the current population does not have sustainable access to safe drinking water. Lack of adequate water resources is one of the leading causes of disease in the developing world. In particular, 1.4 million children die each year of diarrhoeal disease and 50% of all malnutrition is caused by unclean water and inadequate sanitation.

In the 1970s there was discussion over the use of Antarctic icebergs as a source of freshwater. Antarctica has 30 million km³ of water, of which 1250 km³ is locked up in icebergs per annum. This represents 3-4 times Australia’s annual renewable water supply. In Antarctica, the Ross Ice Shelf is seen as the most optimal region for obtaining icebergs in the Pacific region. If single icebergs were harvested, acquisitions in this region could be made year-round between latitudes 60° and 65°. However, a collection of large quantities of icebergs are required in order to benefit from economies of scale. Therefore, ice trains would need to be created.

To improve efficiency of identifying individual small icebergs for an iceberg train, satellite pictures could identify clusters of icebergs most suitable for the train based on size and shape. The Iceberg Water Harvesting Group (IWHG) has developed software that optimizes routing of individual icebergs and includes rough melting kinetics. The software allows each possible iceberg route to be simulated, subject to minimization of energy input for tugboats, travelling time and the maximization of ice mass at the destination site. To steer the iceberg train, each iceberg needs to be a ship shape to reduce friction. On size, each individual iceberg must survive natural melting during the voyage of up to six months through progressively warmer waters, while being exposed to strong winds that enhance sublimation from the iceberg’s surface. It has been estimated that in 18°C waters, the predicted melt rate for icebergs is one meter per day. For the iceberg train to be economically viable, researcher’s Hult and Ostrander estimated icebergs need to measure at least 250-300m in height. As there needs to be a certain volume of water that satisfies the requirements at the end destination, the volume must be calculated to include all loses during the transportation process, resulting in the need of wrapping each individual iceberg.

Antarctic icebergs

Antarctic icebergs

Large-scale wrapping of icebergs has never been conducted before, however, the German Antarctic RV Polarstern, an icebreaker, conducted a small-scale experiment in which it wrapped up a small 3,000 ton iceberg using plastic rolls 2m wide, covering the tip of the iceberg. To protect the underside of the iceberg, the plastic wrap was allowed to sink under its own weight and be carried under the iceberg by the current. If the current was not strong enough, the plastic wrap was drawn under the iceberg using cables. Once the underside of the iceberg was covered, air sacks inside the plastic wrap were inflated causing the iceberg to rise, limiting the area surface exposed to sea water. The experiment involved attaching cables from a floating platform across the top of the iceberg. Air-filled rollers were used to overcome friction. Once the iceberg was fully wrapped up, the plastic wraps were welded together, sealing the entire mass.

However, ships need to be able to prevent rolling of the large-scale icebergs during transit and there are technical difficulties arising from the use of suitable cables required to tow the icebergs, with no commercial cables currently available to tow large-scale Antarctic icebergs. Attempts at evaluating the costs of iceberg transportation are speculative because the technology associated with iceberg harvesting has not been developed. The required infrastructure at the destination site for processing the iceberg is also not known precisely. Components of the cost calculation are generally known and are the costs of iceberg detection, towing, route tracking, transportation, operation and maintenance at the destination port, minimization of pollution loss, sublimation and the construction of suitable storage facilities for the melt-water. A preliminary calculation made by the IWHG, using an expected cost analysis approach, suggests if iceberg water was to be sold to consumers at US$0.50/m³, to satisfy an annual demand of 2,000 Mm³, the total investment made over five years would be approximately US$500 million.

There are numerous challenges to overcome before icebergs can be converted to freshwater. For instance, if iceberg harvesting is to be commercially viable, a large number of icebergs need to be towed in the form of an iceberg train. This requires satellite imagery to detect ideal shapes and sizes that limit form drag and skin friction. The icebergs would also need to be of a specific width and thickness to prevent rolling during transportation. However, it is unlikely suitable icebergs will be in close proximity to one another. An additional issue is the fact that currently it is impossible to tow iceberg trains safely. It is estimated that an initial investment of US$500 million is required to harvest icebergs. This is likely to be out of reach for countries most needy of freshwater as they are mostly developing states.

The take-out

It is more cost effective and environmentally friendly to invest in wells to provide safe, potable water in developing countries than to provide water from Antarctic icebergs in the near and long-term future.

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Author: Robert Brears

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2 Comments

  1. What about storms? It is an interesting hypothesis about using iceberg water. I wonder how it would compare with desalination plants?

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  2. Well appreciating the concept – But to my ideology – if you do so in transporting water from ice, can’t it be a point of reduction in atmospheric evaporation levels which later on a long period will impact on cloud storage. So, as if we reduce evaporation levels by transporting then it leads to more heating condition below the iceberg (because when a net evaporation occurs, the body of water will undergo a net-cooling directly)

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