Sea level is on the rise around the globe. Some areas, such as New York City, however, are seeing the water rise faster than others.

According to the latest IPCC report, the average global sea level has risen about eight inches since 1880.  Locally, in New York Harbor, the water has risen by more than a foot in the past century. The graph below shows the upward sea level trend at the Battery, Manhattan’s southern tip.

In general, sea level rise has two main drivers. They are thermal expansion – a process in which water expands as it warms – and the melting of land based ice, such as glaciers and ice sheets. Both are the result of rising global temperatures. On the local level in NYC, there is also the issue of glacio-isostatic adjustment. This process is not caused by current glacial melt, but rather by the modification of the Earth’s surface as it slowly responds to the removal of the massive weight of ancient glaciers. Overall, it causes some land surfaces to rise and others to sink.  In NYC, the land is slowly sinking.  This combination of factors is expected to intensify future storm surge events in the city.

Sea level is rising in NY Harbor.   Credit: NOAA