WASHINGTON — A climatic quirk seems to be slightly shielding the U.S. coast during busy hurricane seasons, often weakening major storms just as they approach America's beaches, a new study finds.That could help explain why it's been more than 11 years since a major hurricane with winds of more than 110 mph has hit the United States mainland.Last year's Hurricane Matthew was a perfect example of this uniquely American "protective barrier" of stronger crosswinds and cooler coastal waters, according to the study's author, climate scientist Jim Kossin of the National Oceanic and Atmospheric Administration.Matthew devastated Haiti as a monster storm hitting land with 145 mph winds, threatened Florida as a major hurricane and then fizzled as it finally came ashore in South Carolina, barely registering as a hurricane with 75 mph winds.Kossin's study published Wednesday in the journal Nature found that shifts in air and ocean conditions over decades work together to weaken major storms along the U.S. coast. This protective barrier begins around the U.S.-Mexico border in Brownsville, Texas, and gets more noticeable around the Atlantic coast, Kossin said."It's a lucky byproduct for the United States coast," Kossin said. "It's really unfortunate that we're the only ones that seem to be benefiting from this situation."The Atlantic Ocean seems to alternate between cycles of heavy and low hurricane activity.