Seattle, WA


Portland Summary
  • Sea level is currently 0.14 meters (5.5 inches) higher than in 1992
  • Rise rate =  mm/year
  • Acceleration =  mm/year2
  • Projected sea-level height in 2050: 0.37 meters (1.2 feet) above the 1992 height
Chart Interaction

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Legend Abbreviations

To learn more about the terms and abbreviations in the legend, expand the selections below.

MMSL

Represented in light blue, the Monthly Mean Sea Level (MMSL) shows the height of the water at this tidal gauge averaged over a month of measurements. The sharp ups and downs reflect changes in water level due to storms, tidal variations, and changes in ocean and estuarine circulation. Height is measured relative to a standard elevation defined by the National Oceanic and Atmospheric Administration. See detailed discussion.

Quadratic Trend

The quadratic trend, shown in darker orange, indicates that sea level is not only rising at this tidal station, but that the rate of sea-level rise is accelerating with time. In other words, the rate of sea-level rise is best represented by a quadratic curve rather than a straight line. Comparing the quadratic and linear projections shows an exponential rise in sea level will result in a significantly higher sea level in future years. See detailed discussion.

QHi95 and QLo95

Shown in lighter orange, these confidence intervals encompass 95% of the sea-level observations recorded during each month at this tidal station, whether above (QHi95) or below (QLo95) the mean. Extending these intervals forward implies that sea level could be as much as 0.18 meters (7 inches) higher or lower than the best (quadratic) estimate of sea level during any future month out to 2050. See detailed discussion.

Linear Trend

The linear trend, shown in green, indicates how quickly sea level would rise at this tidal station with no acceleration in the rise rate (our analysis suggests this is not the case). We display the linear trend to help clarify that linear projections result in a significantly lower sea level in future years than we expect given recent observations of an accelerating rate of sea-level rise at this station. See detailed discussion.

Decadal Signal

The decadal signal, shown in dark blue, portrays ups and downs in sea level due to relatively short-term interactions between the oceans and the atmosphere, with El Niño as an example. Projections to 2050 made during an upturn in the decadal signal will be higher than they would be if the decadal signal was nearing or at a low. See detailed discussion.

Station Facts
  • Official Designation: Portland, ME - Station ID: 8418150
  • Total Length of Observational Record: 107 years (1910-present)
  • Observational Record used in this Analysis: 48 years (1969-present)