Heat Content Change in the Pacific Ocean between the 1990s and 2000s

We studied the change in heat content in the Pacific Ocean using data from repeat hydrographic surveys. The most recent trans-Pacific surveys along 47°N and 179 °E conducted in 2007 reveal that circumpolar deep water has warmed along 179 °E as suggested by previous studies and also that the deep water was warmer along 47 °N even since 1999. Simple estimates show that the heat content increased in the layer deeper than 4000 m over almost the entire Pacific Ocean. The increase in heat content below 3000 m was about 5% of the ocean-wide increase. Heat content changes in the deep layer are not uniform and a vertical profile of heat content change has a minimum at a depth around 3000 m. The non-uniform distribution of heat content change in the mid- to bottom layer demonstrates the existence of overturn circulation and may indicate that this circulation is changing.