Secrets of the sediment!

One of our scientists aboard the ship, Thibaut Caley, is studying specifically the leakage of water from the Agulhas Current into the Atlantic Ocean.  For the most part, due to various interactions and physical conditions, the majority of the fast-paced, tropical water of the Agulhas gets retroflected back into the Indian Ocean when it gets to the southern tip of Africa.  But there’s always some leakage around the Cape of Good Hope into the Atlantic.

It turns out that the leakage is always greater during interglacial warming periods than during colder glacial periods.  Normally, the southern Atlantic Ocean is very cold, while the Agulhas Current is very warm and salty.  When tropical species of foraminifera are found in the cold Atlantic waters and sediments, it indicates they have been carried there courtesy of the Agulhas.  What’s most amazing to me is that Thibaut can tell the amount of leakage based on the abundance of 5 indicator species of forams  (the Globorotalia menardii above, plus the 4 shown below).  He can tell that the leakage today is one of the largest in the last million years, though the interglacial period 400,000 years ago was the largest known so far.  However, up until this expedition, the sediment record only went back 1 million years.  We have extended that record an additional 6.4 million years!  Who knows what secrets that sediment conceals, but Thibaut will be busy for years to come exposing them.

05041477A-12H-cc P obliquiloculataPulleniatina obliquuloculata

06441479B-2H-cc Globigerinoides ruberGlobigerinoides ruber

06501479B-2H-cc Globigerinoides sacculiferGlobigerinoides succulifer

04031476A-1H-1 mudline G siphonifera(C)Globigerinella siphonifera