La Nina, December 2010. Map showing Pacific Ocean height in December 2010 compared to the average height for that period. Blue areas are lower than average and red areas are higher than average. Water expands as it warms and so warm areas of the ocean are higher than cool areas. The blue area across centre is indicative of a La Nina event. La Nina effects weather systems across the world. In December it caused catastrophic floods in Australia, Sri Lanka and Brazil, and drought in Argentina. Image obtained by the Ocean Surface Topography Mission (OSTM)/Jason-2 satellite.