New York City (NYC) is in for some extreme flooding should another Hurricane Sandy hit the metropolis, thanks to the drastic sea level rise and the storm tide's current maximum height, which also means it will be 20 times more likely to flood than it was 170 years ago, a new study bared.

The research paper accepted for publication in Geophysical Research Letters reported that the lower Manhattan's seawall, which is 1.75 meters or 5.74 feet high, can succumb to the seawaters once in every four to five years, a far cry from the predicted 100-to-400 year estimate back in the mid-19th century.

Worse, a "ten-year storm," or a hard-hitting storm that has a ten percent chance of occurring in any given year, could lash the NYC with greater storm tides by almost two meters or about six and a half feet than normal, as compared to the ten-year storms occurred in the mid-1800, which only reached 1.7 meters or approximately 5.6 feet.

Researchers define the storm tide as "the amount that water levels rise during a storm," which includes both the storm surge (the rise in seawater created by the storm above sea level) and the astronomical tide.

"What we are finding is that the 10-year storm tide of your great-, great-grandparents is not the same as the 10-year storm tide of today," said Stefan Talke, an assistant professor of civil and environmental engineering at Portland State University and lead author of the study.

Scenarios could be reminiscent to the Hurricane Sandy aftermath, where a storm tide at the tip of Manhattan engulfed Battery Park, reaching a 14.06 feet record high, the National Hurricane Center's report on Sandy revealed. With the current state, weaker storms can now even wreak havoc in the Big Apple.

Researchers point to climate change and increasing global temperatures as two main reasons of the sudden upsurge in the sea level.

Meanwhile, the variations and irregularities in the North Atlantic Oscillation that affects the winter weather in Europe, Greenland, northeastern North America, North Africa, and northern Asia also contributed to the increasing storm tides over the years.

"There could also be local factors, like deepening of shipping channels around New York harbor, that could have affected storm tides in the area over the past 170 years," Talke added.

Talke and his team had to painstakingly glean out the tide gauge details from the handwritten notes since 1844, which are stored in the U.S. National Archives in College Park, Md. Each page was carefully photographed to be brought back to Portland for encoding. Erroneous or missing figures were supplied by backtracking newspaper articles about the big storms.

Geophysical Research Letters is a journal of the American Geophysical Union known for its high-impact, innovative, and timely research on major geoscience disciplines.

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