19 January, 1998

Hi Everyone!

We are steaming through more sea ice on our voyage in Ross Sea aboard the 
ice breaker Nathaniel B. Palmer.  We have seen many icebergs and some 
penguins and seals. The penguins are Adelie Penguins, the most numerous 
penguin in Antarctica.  The seals are Weddell Seals.  They are large 
brown seals with some white spots.  They stay in Antarctica all year 
long, and live under the blanket of sea ice in the winter.  They keep an 
air hole open in the sea ice by chewing on the ice!  

Speaking of sea ice - did you try the experiment of freezing some salty 
water?  Did the water get saltier and was the ice that formed less salty? 
In Antarctica the sea ice freezes.  As it freezes, it leaves most of the 
salt behind in the ocean, causing the ocean water to get saltier.  This 
saltier water is more cold and dense than the water around it, so the 
salty water sinks.  The coldest, saltiest water mass in our world's ocean 
is formed in Antarctica this way. This water sinks around the Antarctic 
continent and flows through the deep ocean all the way to the deep ocean 
near the equator!

So, what are we doing in Antarctica?  We are not studying the ocean 
water, we  are investigating the last ice age in Antarctica.  The ice 
sheet covers 98% of the Antarctic continent today.  Scientists think the 
ice was much larger during the last ice age. 

The last ice age was about 20,000 years ago.  If you live one hundred 
years, how many lifetimes is that?  Geologists work in different time 
scales - they are usually interested in changes on our Earth that are 
hundreds to thousands to millions of years old.

Antarctica is surrounded by a sea.  If the ice sheet was much larger, 
that means it grew across the sea floor around the land.  This is why we 
are afloat in a ship and collecting information from the sea floor!  If 
the ice sheet grew, it probably left clues for us to find on the sea 
floor.  Every environment is different.  A beach is different from a 
forest.  A beach has sand and dunes and creatures like crabs and starfish 
and fish.  A forest has trees and soil and animals that live in a forest. 
 If a geologist is studying rocks that contain sands and dunes and 
creatures from near the ocean, chances are that they studying rocks made 
on a beach a long time ago; they would not think the rocks were made in a 
forest.

 A glacier or ice sheet leaves clues behind, too.  A glacier pushes the 
sediment (mud and sand and pebbles)  in front of it, much like a 
bulldozer. It leaves a pile of dirt where it stops. These piles of dirt 
are called moraines.  Glaciers also carve the rock under them, making 
grooves in the rock, called striations.  We are using several instruments 
to image the sea floor, to get a picture of the sea floor.  I will tell 
you about the instruments next time.  We are going to use these 
instruments to see if we can determine how big the glaciers were in Ross 
Sea during the last ice age by looking for the moraines and striations.  
We will collect samples from the sea floor, too. These samples will let 
us look for fossils that will hold clues to the type of environment we 
are studying, much like the fossils of fish and starfish and crabs tell 
us something about the beach!

More soon from the Ross Sea!  I hope you are fine!

E. Shackleton Bear