i've seen this documentary about what u said, i think its call the Global conveyor belt, or sort of, yes, if the tide and current under the sea is affecting, it may cause a change in our weather all around the earth. e.g Places which never encounter Ttornado will start to have it. on the other hand it said that the worse it it affect the northen pole and southern pole, which may accelerate the melting of the iceberg, Its something to do with the water which is cooler and warmer flowing in and out from those places