King tides reflect the future for NH Seacoast as sea levels rise
Seacoast communities have seen a preview of the future this week, as higher than normal tides caused rough surf and flooding of some areas.
This is known as the king tide, the highest of the year, and it occurs when the earth, sun and moon are in perfect alignment, enhancing the gravitational pull on the oceans.
Low-lying coastal areas, especially near marshes, become inundated as the water level rises well above the norm. Even on a sunny and calm day, these king tides can produce flooding in susceptible areas.
This naturally occurring high tide can bring more severe impacts if there is a storm or persistent onshore wind.
For example, the high tide was a bit more severe at New Hampshire beaches on Wednesday, as a northeasterly wind piled up the water at the coastline.
Another round of king tides is coming in just a few weeks. November 14, 15, and 16 will all feature late morning or midday tides matching or even exceeding the height of this week's tides. We will be closely watching for any storms around this time, which would exacerbate the situation.
As the earth warms and sea level rise is accelerated, these higher tides will become a more frequent occurrence. Instead of happening just a few days each year, the tide could reach this level multiple times. The king tide reflects what the more vulnerable parts of the seacoast could look like in the decades ahead.
Since 1880, the sea level is eight inches higher on average. It continues to rise today, and reasonable projections for New Hampshire range from a rise of 1 foot to worst case, 4 feet by 2100.
The good news is preparations are beginning for a changing seacoast. On Friday, the Coastal Risk and Hazards Commission will be releasing recommendations for communities on how to prepare for the impacts of a rising sea level and changing climate.