In late October 2012, an unusual megastorm wreaked havoc on parts of the Caribbean, United States, and Canada. Hurricane Sandy—or Superstorm Sandy—was a massive storm about 1,000 miles in diameter that followed an atypical path. Sandy's unusual path and its merger with another storm caused it to earn descriptive titles like “super” and “mega,” as its high winds, heavy rain, and flooding caused widespread destruction. Sandy caused hundreds of fatalities and more than $60 billion in damage. Although it was no longer classified as a hurricane when it made landfall in the United States (it was designated a post-tropical cyclone because it had lost the characteristics of a hurricane), Sandy will go down in history as a remarkable storm.

It is still unclear if global warming played a role in influencing Hurricane Sandy’s path, and scientists continue to research the effect that warmer temperatures may have on hurricane formation. However, several factors have been identified as contributing to Sandy’s morphing into a “superstorm.” One factor was a warmer ocean-surface temperature in the North Atlantic. At the time of Sandy’s formation, parts of the North Atlantic were about five degrees warmer than normal. The warm air and water vapor at the ocean’s surface made it possible for Sandy to pull in more moisture as it moved north, strengthening the storm and increasing the amount of rainfall. Additionally, a separate winter storm developed inland to the west of Sandy as the hurricane continued to follow a path parallel to the East Coast of the United States. Generally, the paths of these winter storms are influenced by the polar jet stream—a narrow band of strong wind in the upper atmosphere that flows across the middle and northern latitudes. The jet stream typically moves winter storms east across the United States toward the ocean. However, outflow from the hurricane enhanced a high-pressure system just south of Greenland, altering the jet stream and reinforcing a blocking pattern that significantly slowed the movement of the winter storm. The interaction between Sandy and the winter storm to its west produced the westward turn of Sandy, which led to the devastation along the coast.

Hurricane Sandy produced a dangerous storm surge that caused massive flooding in low-lying areas of New York and New Jersey. Recent studies have shown that the Arctic is warming at about twice the rate as the rest of the world. Melting polar ice contributes water to oceans, which raises sea levels. Sea levels are also rising because of increasing temperatures—warmer water takes up more volume than colder water. At least a portion of the damage from the storm can be directly attributed to rising sea levels that enhanced the devastating power of the storm surge. In the New York area, sea level has risen by about one foot in the last century, making the area more vulnerable to coastal flooding. This threat is not just specific to hurricanes, but will be an issue each time a storm of any origin makes its way up the East Coast of the United States.

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