Sudden Rise

Sea Rise 14,200 Years Ago
by University of Oregon, April 2002,
in journal Science

Researchers from the University of Oregon published a study that determined that a very large and unusually abrupt rise in sea levels 14,200 years ago was caused by the partial collapse of ice sheets in Antarctica. The period exhibited conditions similar to today with increased temperatures, sea levels and atmospheric carbon dioxide. Using shoreline fossil deposits scientists were able to develop a method of identifying each possible melting scenario from ice sheets that existed at that time.

According to Peter Clark, professor of geosciences at University of Oregon, "We can't say at this point whether the recent breakup of part of an ice shelf in Antarctica has any relevance to this type of huge meltwater event that originated from Antarctica thousands of years ago. We don't know yet how important these ice shelves are to stabilizing the larger ice sheets of the continent. This event happened near the end of the last Ice Age, a period of de-glaciation that lasted from about 21,000 years ago to 12,000 years ago. The average sea level rise during that period was about eight millimeters per year. But during this meltwater pulse there was an extremely rapid disintegration of an ice sheet and sea levels rose much faster than average."

The University of Oregon report states, "What is very clear, however, is the importance of Antarctica's huge ice sheets remaining stable. The West Antarctic ice sheet is thought to be potentially unstable, and if it collapsed sea levels around the world would rise almost 20 feet. The melting of the larger and more stable East Antarctic ice sheet would raise Earth's sea levels another 200 feet. In less than 500 years at the end of the last Ice Age, this event caused the Earth's sea level to rise about 70 feet. The cause of this event, called the "global meltwater pulse 1A" since it was first identified in 1989, has until now been unknown. This study not only pinpoints the source of the meltwater pulse, but it also makes clear that significant climatic events can occur very rapidly and unpredictably. Prior to the partial collapse of the Antarctic ice sheets 14,200 years ago, carbon dioxide levels had risen about 50 parts-per-million in the atmosphere. [Note: 14,200 / 4 = 3,600.] In the past 150 years, since the beginning of the Industrial Revolution, carbon dioxide levels in Earth's atmosphere have risen 85 parts-per-million."

The research was published in the journal Science. - University of Oregon.