The warming oceans and sea level rise

The world's oceans continue to warm steadily, which is also a contributing factor to global sea-level rise.

Ocean heat content

Image courtesy of NOAA.

As you can see by the graphic above, the heat content of the world's oceans has been steadily increasing since the end of the 20th century.

In addition to sea-level rise, due to the thermal expansion of water, the rise in ocean heat content is also contributing to ocean heat waves, the melting of glaciers that terminate into the oceans and coral bleaching.

Image courtesy of NOAA.

The greatest increase in ocean heat content over the past 20-30 years has been over the northwestern Atlantic and the far western Pacific. The melting of the Greenland Ice Sheet has likely contributed to a surge of cold, freshwater into the far northern Atlantic this century, which has resulted in a loss of heat content in that region.

Global sea level

According to NOAA, the average global sea level has risen 8-9 inches (21-24 cm) since 1880, and that rise is accelerating. The main contributors to sea-level rise are the melting of the Greenland and Antarctic Ice Sheets and the thermal expansion of seawater.

Image courtesy NOAA.

High tide flooding is anywhere from 300 to 900 percent more frequent now than it was 50 years ago along exposed coastlines.

Image courtesy of NOAA

A clear majority of the ocean surfaces in the world are seeing a rise in sea level, while a few small packets, especially in the southern Ocean, are falling slightly.

Even if the world starts to significantly limit the amount of greenhouse gases that are released into the atmosphere, ocean levels by the end of this century will still likely end up about a foot (12") higher than what they were at the start of this century.

However, that increase could be as high as 8 feet if greenhouse gas emissions continue to rise the rest of this century. A change anywhere close to this would greatly alter the world's coastlines and inundate areas that were once highly populated.