Day 13 Land Ahoy!
Photo: The North-East tip of Elephant Island with Cape Petrels in the foreground.
The final CTD of the South America to Antarctica section is achieved
at 7am. It is met with jubilation, elation and relief. Measurements have been
taken along this same line every year bar 2 from 1994 - an unprecedentedly comprehensive
time-series especially considering it is some of the most inhostpitipal territory
known.
Photo Xing Feng (left) manages the Doppler Current Meter thingy while JB and Stevie take blob samples from one of the last casts of the America to Antarctica Section.
Along the way, the no no-nonsense, down to earth Xing Feng
from the Massachusetts Institute of Technology has been managing a lesser known
4-letter acronym: the lowered ADCP. The ADCP stands for Acoustic Doppler
Current Profiler. If you have switched off already because of all this fancy
physics talk...bare with me just a moment...please...please. The ADCP send out
an acoustic signal into the water. If the signal comes back faster than it was
sent, we know the current is coming towards us if it comes back slower we know
the current is moving away from us (this is known as Doppler shift). It is a
bit like throwing a ball at your little brother. If he is running away scared
the ball will hit him and not bounce back very quickly. If he is angry and
running towards you in a fit of rage... the ball will hit you very hard (and probably
so will he). If you have never played brandings or have never had a little
brother...you’ll never get physics...sorry.
So the ADCP can tell
us the current speed all the time...cool huh! We attach it to the CTD (yes I admit
CTD is not a very good name as it does a lot
more than conductivity-temperature and depth ...but anyway). As the CTD sinks and is hauled up, Xing Feng’s
little Doppler thinging measures the speed of the water. This helps us measure the Antarctic
Circumpolar Current and tell us where the Blob of tracer might be heading and
why it might be mixing.
Photo: The North-East tip of Elephant Island with Cape Petrels in the foreground.
Once the last CTD is on board and the last samples have been
taken we see an incredible sight: Elephant Island. As you’d expect, this morning
the ocean is grey, windy, misty, frothy (etc...etc...insert adjectives) and...incredibly...a
mountain juts out of the water and pierces the low lying clouds. It isn’t the
kind of place one would like to be stranded on. Shackleton and his entire where
crew where apparently stranded there before managing to row to South Georgia
and then climb across it...quite a feat it feels like from our temperature
controlled instrument room.
Photo: Navigation charts on the bridge show our path past Elephant Island. (Taken by Gwyn)
Day off today! Hooray! Time to explore this Bar thing they
have on the boat...
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