Dispatch 14: Mooring Ops Day 2     Print

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David Jones and Andrey Proshutinsky

September 19, 2017

Weather: cloudy, 5 knot winds, scattered ice covered seas

Temperature: -2 C

Relative humidity: 96%

Location: Beaufort Sea, 77˚ 59’ N; 149˚ 52’ W

News

If you look at our position today and compare it to yesterday's position you could easily infer that we have been in the same place for the past day...but we have not. After the mooring was recovered yesterday we made our way towards the southeast to station CB12.5 at 77˚ 30’N, 145˚ 00’W. At station CB12.5 we did the scheduled CTD cast and then turned around and came back, so we started today in the same spot as yesterday with a few nautical miles covered out-and-back in between. AND we are back where we started because today is mooring deployment day.

This mooring goes in "anchor first" according to Josh Mitchell the WHOI Mooring Technician. Basically it involves lowering a 4000 pound anchor to the sea floor 3800 meters down, with all kinds of stuff strung together on a cable then finally ending with a subsurface buoy about 30 meters below the surface. Jim Ryder, the Lead Mooring Technician, follows a carefully thought out schematic step by step to get it all deployed as efficiently as possible. Jim works with the ship’s Bosun, Rico Amamio, who does all the on-deck directing of the cranes and lifts and spoolers, to make it happen.  If all goes well it will take 6 to 8 hours to complete and there will NOT be a tangled knot of cables, chains, clothing, and science instruments on the deck when the dust has settled.

An "anchor first" mooring is just that–the anchor goes in first. It is then followed by a string of deep floats that will help to return the anchor release mechanism and the bottom pressure sensor to the surface when it is retrieved. Next in line is several very long lengths of cable followed by the profiler. The profiler travels up and down an approximately 2000 meter length of cable collecting data on various parameters of interest. Right towards the very top of the string a couple of other instruments are positioned, including a pair of SAMI's which will measure and record the CO2 level and pH level. Finally it is all connected to the very top piece that is the bright yellow sub-surface buoy. The photos that follow attempt to capture the deployment sequence...sort of.

Some Beaufort Gyre Science: Arctic climate decadal variability

In the beginning of the 1960s, Z. Gudkovich (Arctic and Antarctic Research Institute) analyzed the distributions of atmospheric pressure in the Arctic. He concluded that seasonal changes of winds over the Arctic Ocean have two dominant regimes: clockwise (or anti-cyclonic) and counterclockwise (cyclonic) circulation. This observation helped improve the understanding of sea ice seasonal variability and new methods of sea ice predictions were developed. In the 1990s, A. Proshutinsky and M. Johnson simulated circulation of ice drift of the Arctic Ocean from 1946 to 1996 and corroborated Gudkovich’s hypothesis about two seasonal regimes of ice motion in the Arctic.

Moreover, they also found that cyclonic and anti-cyclonic circulation regimes alternate every 5 to 7 years with decadal periods (from 10 to 14 years). Figure 14-15 illustrates this decadal variability. From 1946 to 1996, there were four cyclonic and four anti-cyclonic circulation regimes. Each regime has shown pronounced anomalies in all environmental parameters: sense of atmospheric circulation and ice and ocean motion; air temperature, cloudiness, sea ice concentration and thickness, oceanic freshwater and heat content, frequency and strength of storms and storm surges, etc. There is a hypothesis that during anti-cyclonic circulation regimes (see Figure 14-16), the Arctic Ocean accumulates fresh water and the climate of the North Atlantic tends to warm up. During cyclonic circulation regimes, the Arctic Ocean releases fresh water from the Beaufort Gyre region and the North Atlantic climate cools down. These periods of fresh water release from the Arctic Ocean are called “Great Salinity Anomalies” (sea Figure 14-16 for details).