ARTYKUŁY INFORMACYJNE Zmiany poziomu morza – przyczyny, skale czasowe i historia ich poznania
Abstract
Sea level changes – causes, time scales and the history of their recognition.
A b s t r a c t. Sea level changes provoked by multiple forcings that act in a wide range of time scales attracted human interest for several millennia. However, the bases of modern understanding of this phenomenon and its quantitative expression were achieved during the last two centuries. At present, owing to a series of altimetric observations made by 4 satellite missions in the last 30 years, the mean sea level (MSL) rise calculated for the whole Earth is estimated to be 3–3.5 mm per year, with at least half of this value being attributable to human-induced climate warming. About 125,000 years ago, during the last interglacial (Eemian) that was warmer than the current period, the MSL was about 5 m higher than today. Approximately 116,000 years ago, the sea level began to decline as a result of gradual cooling of the climate that led to glaciation, which in the Northern Hemisphere had a climax at 20–30 ka BP. The transition from the last glacial maximum to the current warm period, covering the last 20,000 years, includes the transfer of about 35·106 km3 of water from melting ice caps of the Northern Hemisphere to the oceanic reservoir, causing an increase in sea level of about 130 m. The average rate of MSL rise was about 10 mm per year, although over the last seven millennia, the MSL rising rate dropped to about 1–1.5 mm per year. These changes are considered representative of the natural variability of the Earth's climate system over the past 2 million years.
A b s t r a c t. Sea level changes provoked by multiple forcings that act in a wide range of time scales attracted human interest for several millennia. However, the bases of modern understanding of this phenomenon and its quantitative expression were achieved during the last two centuries. At present, owing to a series of altimetric observations made by 4 satellite missions in the last 30 years, the mean sea level (MSL) rise calculated for the whole Earth is estimated to be 3–3.5 mm per year, with at least half of this value being attributable to human-induced climate warming. About 125,000 years ago, during the last interglacial (Eemian) that was warmer than the current period, the MSL was about 5 m higher than today. Approximately 116,000 years ago, the sea level began to decline as a result of gradual cooling of the climate that led to glaciation, which in the Northern Hemisphere had a climax at 20–30 ka BP. The transition from the last glacial maximum to the current warm period, covering the last 20,000 years, includes the transfer of about 35·106 km3 of water from melting ice caps of the Northern Hemisphere to the oceanic reservoir, causing an increase in sea level of about 130 m. The average rate of MSL rise was about 10 mm per year, although over the last seven millennia, the MSL rising rate dropped to about 1–1.5 mm per year. These changes are considered representative of the natural variability of the Earth's climate system over the past 2 million years.