Dispatch 18: The Only RAS     Print

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Location: 75° 0’ N 150° 0’ W

Weather: -2°C (28°F), Mostly cloudy, lightly choppy seas, North winds at 8 knots, seawater temperature 0.1°C (32.3°F)

Sea Ice: None

We recovered mooring A today, and one of its instruments was unique.  It was the only mooring to have a Remote Access Sampler (RAS) on it.  The RAS takes a water sample every 8 days for a total of 48 samples across the year.  Having a sampler in the ocean for a whole year is important because it allows scientists to capture seasonal and yearly variations.  The JOIS/BGOS cruise is always scheduled for roughly the same time each year (late August–early October), making samplers an important tool to improve the temporal resolution of the data (basically a better data set across time.)

How does the RAS work?   Well, the RAS has a main sample line that rotates to fill a different bottle using its onboard pump.  The sample containers have a bit of mercuric chloride (HgCl₂) in them, which preserves the water after it is sampled.  And of course, the Arctic Ocean is plenty cold, so it helps minimize any changes in the chemistry of the water as the sample waits to be recovered. 

The RAS samples are of interest to track seasonal changes in ocean acidification and nutrients – primarily nitrogen in the form of nitrate. RAS samples are also analyzed for oxygen isotope ratio or delta¹⁸O.  delta¹⁸O is actually the ratio of two oxygen isotopes delta¹⁸O and delta¹⁶O.  As seawater evaporates, more delta¹⁶O enters the atmosphere and some of that eventually falls on land as rain or another form of precipitation.  This precipitation eventually finds its ways into rivers, meaning river water has a higher portion of delta¹⁶O.  Measuring delta¹⁸O then gives scientists an idea of whether the fresh water from the Beaufort Sea came from riverine inputs or from sea ice melt.

Just a quick update on our Styrofoam cups.  They were successfully sent to the bottom of the Arctic Ocean and arrived back on the ship quite a bit smaller.  Their designs remained intact and were indeed improved by their miniaturization.  Check out the pictures to see them small!