The consequences of global environmental change have meant that the need to effectively monitor the world’s oceans has become an important issue. We are witnessing the fastest levels of change in our oceans with the most recent ‘State of the Climate’ report revealing that 'the year-to-date (January-September 2015) globally-averaged sea surface temperature was 1.24°F (0.69°C) above the 20th century average and the highest for January–September in the 1880–2015 record. This value surpassed the previous record of 2010 by +0.11°F (+0.06°C).’ (links to more detailed monthly/yearly reports can be found here: https://www.ncdc.noaa.gov/sotc/).
Many climate change experts have now also said that even if the current levels of greenhouse gases in the atmosphere were to be frozen, the sea would actually continue to warm for centuries, perhaps even millennia and, as this continues, sea levels will continue to rise too as the ocean continues to expand.
In 1999, Argo, a global fleet of more than 3000 free-drifting, profiling floats that measure the temperature and salinity of the upper 2000m of the ocean, was introduced.
The following animation explains how Argo works: ftp://kakapo.ucsd.edu/pub/argo/slides/argo.avi
Prior to the introduction of Argo, monitoring of the changes occurring in the oceans was extremely difficult and hence any trends described were based on limited datasets – for instance the researchers behind Argo cite a recent analysis which concluded that ‘the currents transporting heat northwards in the Atlantic and influencing western European climate had weakened by 30% in the past decade’. This result, however, was based on only 5 measurements spread out over the course of 40 years, making it hard to establish whether this change was part of a wider trend that may lead to disruption of the Atlantic currents or simply down to natural variability. It also makes the importance of improved global ocean monitoring abundantly clear.
The following animation explains how Argo works: ftp://kakapo.ucsd.edu/pub/argo/slides/argo.avi
Prior to the introduction of Argo, monitoring of the changes occurring in the oceans was extremely difficult and hence any trends described were based on limited datasets – for instance the researchers behind Argo cite a recent analysis which concluded that ‘the currents transporting heat northwards in the Atlantic and influencing western European climate had weakened by 30% in the past decade’. This result, however, was based on only 5 measurements spread out over the course of 40 years, making it hard to establish whether this change was part of a wider trend that may lead to disruption of the Atlantic currents or simply down to natural variability. It also makes the importance of improved global ocean monitoring abundantly clear.
Map to show the positions of floats that have delivered data within the last 30 days (source:http://www.argo.ucsd.edu)
So what has Argo told us? Well, as it stands the global dataset produced is simply not over a long enough time-frame to provide us with any observable global change signals; natural seasonal and interannual variability dominate the current 10-year globally-averaged time series. However, our future capabilities to observe the effects of climate change on our oceans rely on Argo's contributions. As such certain parts of the global ocean remain relatively unmonitored, for example, there are relatively few Argo floats in the Arctic and Indian Oceans. Therefore, estimates of ocean warming in these regions are relatively uncertain. Additionally, it is now thought that warming extends below 2000m and a new project, Deep Argo, sets to rectify this by establishing a similar array of floats to monitor the ocean to a depth of 6000m.
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