Observations of Sea Level Rise

Sea level has been systematically measured by tide gauges for more than 100 years. Other direct and indirect observations have allowed oceanographers to estimate (with lower precision) past sea levels going back many thousands of years. We know that sea level has risen more than 400 feet (120 meters) since the peak of the last ice age 26,000 years ago, with periods of rapid rise predating a relatively steady level over the past 6,000 years. During the past few decades, tide gauge records augmented by satellite measurements have been used to produce precise sea level maps across the entire globe. These modern records indicate that the rate of sea level rise has accelerated since the mid-19th century, with possibly greater acceleration over the past two decades (Figure 2.6). The exact amount of sea level change experienced in different locations varies because of different rates of settling or uplift of land and because of differences in ocean circulation.

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