Sea Level Rise at the End of the Ice Age: A Detailed Analysis
At the end of the last glacial maximum around 20,000 years ago, significant changes occurred in sea levels as large ice sheets melted. The rate of sea level rise varied over time, but it is estimated that during the initial deglaciation period, sea levels rose at an average rate of about 1 to 2 meters per century (Fig. 1). However, in some periods, particularly between about 14,000 and 7,000 years ago, the rate of sea level rise may have been even higher, reaching up to 5 to 10 meters per century in certain regions.
These rapid rises were driven by the melting of massive ice sheets covering North America and northern Europe, as well as the thermal expansion of seawater as it warmed. By approximately 7,000 years ago, the rate of sea level rise had slowed significantly, stabilizing to rates more similar to those observed today (Fig. 2).
The sea level initially rose at a rate of about 10 millimeters per year (1 meter per century) during the initial melting phase of the last glacial maximum, which occurred around 19,000 to 7,000 years ago. This rate gradually slowed over time as the remaining ice sheets and glaciers melted.
During the last glacial maximum, which occurred about 18,000 years ago, ice sheets covered Northern Europe, Canada, Alaska, and parts of the northern USA. The melting of this ice mass took around 8,000 years, causing global sea levels to rise about 130 meters. According to Kurt Lambeck and co-authors, between 16,500 and 8,200 years ago, sea levels rose at an average rate of 12 meters (40 feet) per 1,000 years, or 0.12 cm/year (half an inch per year). During this time, there were short periods of rapid sea level rise when large masses of ice quickly melted, known as melt-water pulses (Fig. 3).
The first melt-water pulse occurred between 14,500 and 14,000 years ago, when sea level rose 4 cm per year, or approximately 1.5 inches per year. A second melt-water pulse occurred from 12,500 to 11,500 years ago.
Approximately 89 percent of the ice melted over the last 15,000 years. The ocean returned to its rise but some land previously burdened by the weight of a couple of miles of ice returned to its original state (Fig. 4).
By understanding the complex dynamics of sea level rise during the last glacial maximum, we can better predict future changes and prepare for the potential impacts of climate change on our coastal areas.