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Environmental Monitoring


November 2012 Issue

Arctic Sea Ice Shatters Previous Low Records, NSDIC Says
In September, sea ice covering the Arctic Ocean fell to 3.41 million square kilometers, the lowest extent in the satellite record, which began in 1979. Sea ice extent averaged for the month of September was also the lowest in the satellite record at 3.61 million square kilometers, the National Snow and Ice Data Center (NSIDC) said.

This follows on August's previous record low of 4.72 million square kilometers.

The near-record ice melt occurred without the unusual weather conditions that contributed to the extreme melt of 2007, when winds and weather patterns helped melt large expanses of ice. This was likely because of the loss of multiyear ice.

'It looks like the spring ice cover is so thin now that large areas melt out in summer, even without persistent extreme weather patterns,' NSIDC Director Mark Serreze said. A storm that tracked through the Arctic in August helped break up the weakened ice pack.

This data places 2012 as the lowest ice extent both for the daily minimum extent and the monthly average. The ice extent was 3.29 million square kilometers below the 1979 to 2000 average.

This summer's low ice extent continued the downward trend seen over the last 33 years. Scientists attribute this trend in large part to warming temperatures caused by climate change.

SMOS and Argos Floats Provides New Salinity Map Every 5 Days
The European Space Agency is comparing readings of sea-surface salinity from Argo, a network of drifting autonomous floats in the ocean, to confirm the Soil Moisture and Ocean Salinity (SMOS) water mission's satellite measurements.

Argo is one of the major networks of in-situ drifters, with more than 3,500 active drifters. The Argo floats acquire in-situ data in the upper 2,000 meters of the ocean.

These measurements are then directly compared to SMOS data, which in turn cover the global ocean and provide measurements of the salinity in the first centimeter of the sea surface.

The advantage that SMOS has over the Argo floats is that the satellite provides a complete view of the global ocean every five days. Argo measurements provide salinity data sampled at a lower resolution than SMOS every 10 days. The higher precision provided by the Argo floats, however, complements the SMOS measurements.

SMOS provides measurements averaged over a surface of 40 by 40 square kilometers, but the difference of the size of the area measured and other influencing factors, like background noise, lead to differences between SMOS and Argo measurements.

'Since Argo measurements are taken much deeper than SMOS's, the stratification of the upper layer of the ocean needs to be taken into account when comparing the two salinities in rainy regions,' said Jacqueline Boutin from France's Laboratory for Oceanography and Climate. 'For example, rain over the ocean will cause SMOS to pick up lower salinity readings than Argo.'

There are many factors that can affect SMOS data quality, like temperature. SMOS measurements have proven to be more accurate in warmer waters where the signal-to-noise ratio is more favorable.

In addition, radio signals transmitted in the same frequency range that the satellite uses to collect data can impede the measurements, meaning SMOS salinity is more accurate in areas with less radio-frequency interference.

The mission is now approaching its objective of 0.1 practical salinity unit accuracy for a 10-to-30-day average, over an open ocean area of 200 by 200 kilometers.

Students Design Device to Track Movements of Marine Animals
Students from Dalhousie University are developing an accelerometer-based tag to track the movements of marine animals.

The device is designed to collect data that would help researchers learn more about fish behavior and growth based on the movement of the tail—important information for fisheries. Presently, there is no reliable measurement of growth rate in the field.

The students, Franziska Broell and Andre Bezanson, developed the tags by adapting open-source hardware developed by the Arduino electronics community. The tags can sample up to 500 movements per second.

'The first version was a lot larger and it needed a lot more power. Since then I've been able to refine it to eliminate components and simplify the design,' Bezanson said.

In January, Broell will bring her fish back to the university to fit them with the latest version of the accelerometer. By then, the fish will have grown, and she will re-do all previous experiments done with older models of the accelerometers to see what kind of influence the change of size has on the movement of their tails.

Half of Great Barrier Reef Coral Lost Due to Storms, Starfish
The Great Barrier Reef has lost half its coral cover in the last 27 years. The loss was due to storm damage (48 percent), crown of thorns starfish (42 percent) and bleaching (10 percent).

If the trend continued, coral cover could halve again by 2022, according to a new study published in the Proceedings of the National Academy of Sciences in October by researchers from the Australian Institute of Marine Science.

The researchers suggest that by reducing crown of thorns populations, improving water quality and developing alternative control measures, further coral decline could be prevented and improve the outlook for the Great Barrier Reef.

The researchers noted that such strategies can, however, only be successful if climatic conditions are stabilized, as losses due to bleaching and cyclones will otherwise increase.

Without crown of thorns, coral cover would increase at 0.89 percent per year, so recovery would be slow.

Southern regions of the reef sustained most of the damage, while northern coral cover stayed relatively stable. Two severe coral bleaching events have also had major detrimental impacts in northern and central reefs.

The findings are based on the institute's reef-monitoring program, which began surveillance of more than 100 reefs in 1985 and has incorporated more detailed annual surveys of 47 reefs since 1993.


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