The height of the sea surface relative to the land. Eustasy is the rise and fall of the sea level globally.
The most important factors in raising the global sea level are increased melting of ice on land, and the expansion of the ocean water as it warms.
With increased satellite coverage more accurate measurements of the global sea level have become available. According to the IPCC the records, since the early 1990s, indicate that the sea level has been rising by about 3 mm a year, and this rate is expected to increase in the future.
The present rise of the sea level is mostly due to the expansion of the sea water. How much the melting of land ice will contribute in the future is still unknown. Potentially the release of water from the ice could raise the sea by many meters.
Although the global sea level is rising, there may be regional differences. Changes in the ocean currents and regional temperature differences can create large regional variation in the change in sea level. In some areas the sea level may rise by several times the global average, while in other areas it may fall.
Today there are also significant regional differences in the sea level when viewed on a global scale. The Atlantic Ocean is about 1 meter lower north of the Gulf Stream than further south. Compared to the Pacific, the Atlantic as a whole is approximately 40 cm lower.