U.S. GO-SHIP I6S 2019

Cruise Plan

Track

Steaming of 2066 nm is estimated from Cape Town to the beginning of the I6S line in 2019, only stopping at some intermediate location to occupy a test cast.

Three segments are envisioned for the 2019 reoccupation of the 2008 I6S cruise, based on past endpoint and course-change locations.

The first station will be located at the Antarctic shelf break ~31.5ºE, or near the 500-m isobath. From there, a 39-nm section will cross the Antarctic slope and it will include 9 closely-spaced stations.

 

At 68ºS the cruisetrack will turn to the north and continue along 30ºE for 1980 nm. This meridional segment will end at 35ºS and will include 66 more stations spaced at a nominal 30 nm.

 

The final 144-nm segment will extend to the northwest and end near the 300-m isobath of the South African continental shelf (28ºE, 33.2ºS). It will incude 16 stations with shorter spacing, from 16 nm to 2 nm, toward the coast.

 

Timetable

Conservative steaming times are estimated assuming ship speeds of 10 knots from Cape Town to the first station location, 4 knots across the Antarctic continental slope, 8 knots along the 30ºE, and 6 knots along the final northwestward bend. They render transit times of 10.76 days, 0.41 days, 10.31 days, and 1 day, respectively.

Assuming stations with 18 bottles are occupied on the Antarctic slope segment and a minimum of 1 hr requirement for bottle sampling at each station, the estimated total sampling time for Stations 1-9 is 8 hrs, is less than the 9.75 hrs (0.41 days) of estimated transit time. This is also the case for the estimated sampling time of 36-bottle and 30-bottle stations along the 30ºE and northbend segments. A conservative ship positioning and rosette preparation time of 20 min at each station adds a total of 1.26 days.

Conservative at-station times are calculated assuming relatively slow winch speeds, both while lowering (50 m/min) and rising (30 m/min) the rosette. At each station, soaking for 1 min, fudging for 10 min and bottle tripping for 0.5 min are assumed in these rough estimates. The average water depth for the 9 (18-bottle) stations along the Antarctic slope section is 2,116 m; 4,877 m for the 66 (36-bottle) stations along the 30ºE section ; and 3,000 m for the 16 (30-bottle) stations along the final northwest section. The estimated at-station times are 0.86 days, 13.43 days, and 2.11 days, respectively.

A very rough estimate of about 38 days results from 20.23 days of steaming, 1.26 days of ship preparing for stations, and 16.4 days while at station.