Why Observe the Ocean?

The Pacific Ocean has many cycles that Pacific Islanders have been familiar with for thousands of years. For example,

·         People living in Micronesia and Melanesia are familiar with rainfall changes caused by the monsoonal seasons,

·         Over the summer months of each respective hemisphere, cyclones (typhoons, hurricanes) become more likely,

·         Islands such as Fiji and Vanuatu expect more rainfall in the months October to May, as the South Pacific Convergence Zone (SPCZ) changes in position and becomes more active.

However, sometimes these cycles change. Sometimes the rains do not come, or cyclones occur more often in some parts of the Pacific.

Many of these changes are driven by the Pacific Ocean. By observing what the Pacific Ocean is doing, we can see these changes coming and prepare accordingly.

As an example, in late 1982, the usually reliable and strong easterly winds (blowing towards Asia) became weak. This caused the warm water in the Western Pacific to ‘slosh’ into the Central Pacific, which led to heavy rain and flooding in the Central Pacific and much less rain in the Western Pacific. Australia and Indonesia experienced severe drought and forest fires and the anchovy fishery in South America had a huge drop in their harvest.

A NOAA report noted that “... the overall loss to the world economy in 1982-1983 as a result of the climate changes amounted to over $USD 8 billion. The toll in terms of human suffering is much more difficult to estimate.” (http://www.atmos.washington.edu/gcg/RTN/rtnt.html).

This strong El Niño event highlighted the direct societal and economic benefit of monitoring the Pacific Ocean.

In 1984, several moorings were deployed across the equatorial Pacific to monitor the temperature of the surface and subsurface ocean, and send this data back to shore in real time. The array was known as the Tropical Atmosphere and Ocean (TAO) array and is now a key tool used to predict seasonal climate.

Dedicated scientific ships are required to maintain the TAO array of buoys. But in 1986, commercial ‘ships of opportunity’ (i.e. container vessels) were used to drop temperature probes (XBTs) along regular trade routes across the Pacific Ocean. This allowed a larger picture of what was happening in the Pacific Ocean, however there were still large gaps where container ships did not regularly go.

This gap in observations has been filled by one of the most significant recent advances which occurred in 2002 with the beginning of the Argo array of profiling floats. Approximately 3,500 of these floats are currently drifting around the ocean. Each float sinks to 2000m then climbs to the surface every 10 days to get a profile of subsurface temperature and salinity. This data is sent back to shore via satellite and made publicly available to now give us an almost global dataset on the subsurface ocean.

Back in 1984, human caused climate change was just beginning to become widely recognised as a significant issue in the scientific community. However, given that 90% of the extra heat retained by the earth due to increased greenhouse gasses is taken up by the ocean, and the resulting thermal expansion and sea level rise has huge impacts on global society, these measurements are critical.

The measurements have proven that the ocean is indeed warming, that this is very likely due to human activity, and that this is leading directly to sea level rise.


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