Sea level the warmer water expands. For at least the last 100 years, sea level has been rising at an average rate of about per year. Most of this rise can be attributed to the increase in temperature of the sea and the resulting slight thermal expansion of the upper of sea water. Additional contributions, as much as one-quarter of the total, come from water sources on land, such as melting snow and glaciers and extraction of groundwater for irrigation and other agricultural and human uses. Pilots can estimate height above sea level with an altimeter set to a defined barometric pressure.
Weddell Sea Bottom Water exposes more surface water to the wind allowing it sink. This makes the WSBW colder than normal allowing it to inject colder water into much of the world's oceans. If the ENSO even is weak enough, the surface winds off the Antarctic coast can shift direction which creates a reduction in shelf water. This will warm the WSBW as it does not have as much access to the cold, dense surface water. Weddell Sea Bottom Water Weddell Sea Bottom Water (WSBW) is a subset of Antarctic Bottom Water (AABW) that is at a temperature of -0.7 °C or colder. It