Are You Smarter Than a 3rd Grader?

Our school has a competition every year for the 3rd and 4th graders called "Battle of the Books." This year, Sophie's team was the 3rd grade champions (yay!!!). They read a selection of 10 or so books, from which questions are taken by the 3rd and 4th grade teachers. In a tournament style competition, the teams (3 children per) answer the trivia questions to determine the winner. Today was the battle between the top 3rd grade team, the Wildcats, and the top 4th grade team, Rabid Reading Rabbits. When the 4th grade team entered in matching t-shirts with their team name embroidered on the front, and bunny tails on the back, wearing bunny ear headbands, I thought to myself, "Man, these boys are dead serious." Todd thought, "What a bunch of geeks."

It looked promising in the beginning with the Wildcats keeping pace with the Rabbits. Then the Rabbits biffed a question, and the Wildcats were ahead. We were hopeful until the Wildcats got a question they answered incorrectly, and the Rabbits stole it from them for a bonus 3 points.

So, to salve Sophie's wounded pride, I thought I'd pose the deciding question to see how many of you would've known the answer, without looking it up. (Comments are encouraged!):

A large body of cold surface water in the Pacific Ocean that can cause severe weather fluctuations and damage is called _______________.