Global sea levels are rising
Global sea level was nearly stable in the 1800s, but began to increase around the early 1900s, and started to speed up from the 1930s onward.

According to a 2007 report by a large international IPCC group of climate change scientists, the average global sea-level rise will vary from 18 cm to 59 cm (7.09 in to 23.23 in) by 2100.

New research says global sea level rise could be much higher
New research shows that the IPCC models did not account for faster than expected melting of the large polar Greenland Ice Sheet. Because this is land ice, when it melts, it will add substantially to global sea-level rise.

Look at the graph to the right to see that this new research estimates a global sea-level rise of between 0.6 m and 1.2 m (2 and 4 ft) by the year 2100.

Observations tell us regional sea levels are rising as well
Along the US East Coast, the sea level has been rising since the late 1800s at a faster rate than at any other time during the past 2,000 years. It has been rising 0.2-0.3 cm per year (0.08-0.12 in per year) along most of the US Atlantic and Gulf coasts. Overwash flooding due to increased storm surges compounded by sea-level rise will likely become a common event.

What does the future hold for Assateague Island?

More intense storms and changing habitats are likely. Over time, the effects of the natural geomorphology and climate change are expected to become the dominant forces shaping the character of Assateague Island. A sea-level rise of 0.09 to 0.23 m (3.5 to 9 in) by 2040 may claim some of the barrier Island’s valuable landscape. On a high tide, coastal storms will result in increased flooding and overwash. Overwash will add some new land to the bayside marshes and the barrier island will continue, if not speed up, its natural rollover westward.

Park boardwalk washed away. Bay-side erosion. Vulnerability of park facilities.
It will be the pace of sea-level rise that is key!
How fast sea level rises will be the determining factor in the ability of habitats, plants, and animals to adapt.

Salt marshes are particularly vulnerable
The salt marshes of Assateague Island provide an example of why the pace of sea-level rise matters. If not for the occasional overwash that reaches across the island during large storms and deposits sand, the salt marshes would settle and sink below sea level from a lack of new land rebuilding them. This settling of land is called subsidence. Fortunately, in the past, the natural processes of marsh subsidence and overwash rebuilding have been in balance.

But if sea level rises faster than the salt marshes can be rebuilt by overwash, the low marshes may subside, be submerged, and become deep water, eliminating the marsh and mudflat habitats for the plants and animals that live there.