Climate change and rising seas are trouble enough. Now, factor in the lunar wobble
By ANDREW S. LEWIS NJ Spotlight
Flooding from storms and rising sea levels are always at the top of the minds of planners and residents along the New Jersey coastline. But a NASA report published last month in the journal Nature Climate Change has heightened worries about another, unexpected threat for shoreline communities: the lunar wobble.
The report highlighted a common phenomenon that humans have known about for centuries — that the moon’s orbit around the Earth is tilted at about 5 degrees, and that path fluctuates over time.
“It’s a wobble in the sense that, if you spin a top, as it starts to slow down it begins to wobble,” said William Sweet, an NOAA oceanographer and one of the report’s authors. “And that’s what we call a declination of the moon’s nodes, which affects the angle at which it is to the Earth.”
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The cycle of that wobble is 18.6-years, and for half of that period the gravitational pull of the moon suppresses regular daily tides — high tides are lower than normal and low tides are higher than normal. During the other half, it’s the opposite: High and low tides are amplified.
“The moon is in the tide-amplifying part of its cycle now,” NASA wrote in a synopsis of the report. “However, along most U.S. coastlines, sea levels have not risen so much that even with this lunar assist, high tides regularly top flooding thresholds. It will be a different story the next time the cycle comes around to amplify tides again, in the mid-2030s.”
Another recent report from NOAA found that New Jersey experiences an average of just over eight days of sunny-day, or nuisance, flooding a year. However, if global fossil-fuel emissions continue at the current rate, and more robust flood mitigation infrastructure is not built, the annual rate of nuisance flooding will likely be two times to three times greater.
When lunar wobble gets serious
Such an increase in nuisance flooding driven by sea-level rise will make what was once an inconspicuous episode — the lunar wobble — into a serious issue with serious implications.
One of the primary reasons for the study was to tease out specific stressors in the environment to get a clearer picture of the myriad factors that play into sea-level rise, Sweet said. It’s important for people to understand, Sweet continued, that a flooded street at the Shore might be due to a single thing, like wind direction, the full moon, a global weather pattern like El Niño, or something else — or any combination of them all.
“We’re trying to increase awareness and preparedness so communities have the resources in hand or budgeted so they can respond appropriately,” Sweet said. “It’s not to scare people; it’s to inform them that, unless you change, here are some pretty good estimates of your risk.”
In New Jersey, virtually every stretch of shoreline is impacted by nuisance flooding, from Trenton south, around the Delaware Bay, and up the coast to Hoboken. And with the very likely chance that sea level will be a minimum of three inches higher by 2030, an additional inch or two of standing water, thanks to the lunar wobble, could translate into costly damages for the lowest-lying municipalities.NASA report signals a flooded future for New Jersey amid increased signs of climate change
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