From Hakai Magazine, June 8:
Compared to what we’re seeing now, hurricane activity in the region used to be much, much higher.
The 2021 Atlantic hurricane season was the third most active in 171 years of record-keeping. The 2020 season was even worse—there were so many tropical cyclones that meteorologists tore through their list of possible storm names and needed the Greek alphabet to keep track of the overflow. But a new study shows that even this flurry of activity may be something of a lull in the centuries-long record of Atlantic hurricanes.
The evidence that hurricane activity is at a historical low is hiding on the Caribbean seafloor, tucked away in odd geological features called blue holes. These open pits form in limestone, often above collapsed caverns. Prolonged erosion weathers the edges into an eerily circular shape.
Blue holes are similar to sinkholes but on a much grander scale. They can be 300 meters deep, like the Dragon Hole in the South China Sea, or 300 meters wide, like the aptly named Great Blue Hole in Belize. The Bahamas is home to the world’s greatest concentration of blue holes, making it an appealing destination for paleotempestologists—scientists who study historical tropical cyclone activity.
The seafloor at the base of a blue hole acts like a calendar of past storms. Much like an ice core or tree ring grows season after season, the sediment at the bottom of a blue hole builds up over time. Natural currents coax a sugary sprinkle of small sand grains into the hole, while violent hurricanes pitch larger grains into the pit. By comparing layers of coarse and fine grains in this sedimentary lasagna, researchers can count how many hurricanes passed nearby. What makes a blue hole a valuable long-term record is that once this sediment settles, there’s very little activity in the pit to disturb it.
Hine’s Hole, a 340-meter-wide hole that penetrates the seafloor in the western Bahamas, offers a prime example of a blue hole hurricane record. It sits halfway between Cuba and the Florida Keys and is far from any landform, so it can chronicle weaker storms that blow in from any direction. The base of the hole is also low in oxygen, so no animals live there to disrupt the delicate sediment. A steady surface current shooting over the hole sends two to three centimeters of sand tumbling into Hine’s Hole each year.
Hine’s Hole, says Tyler Winkler, a geologist at the Woods Hole Oceanographic Institution in Massachusetts who led the study, has the highest sedimentation rate of any blue hole he and his colleagues have seen.
For the new study, Winkler and his team drilled 18 meters into the sediment at the bottom of Hine’s Hole, recovering cores representing the past 540 years of deposition. After comparing the top layers to the modern hurricane record, the researchers have high confidence that Hine’s Hole recorded every Category 2 or higher hurricane within 75 kilometers. Analyzing the cores even further shows that the number of tropical cyclones roiling this corner of the Bahamas is in a historical lull.....
....MUCH MORE
This research is all well and good and in fact is pretty darn creative but what I would like to know is what the action was like during previous warm periods. Unfortunately we run into what is almost an event-horizon, beyond which, like the black hole's event-horizon, we can't observe
As noted in the outro from "How Wall Street Is Gaming ESG Scores":
When a business/finance researcher uses language like "With supercharged hurricanes, massive floods and unprecedented wildfires sweeping the globe" you can tell he's a newbie to the science.
Just yesterday I was looking for hurricane data from the Roman Climatic Optimum and the Minoan Warm Period and the so-called paleotempestology gets pretty sparse at even 1200 years ago, much less 2000 and 3500.
And that's just a moment ago in time. If we are looking back to previous interglacial periods what were the hurricanes like in the Eemian interglacial, 125,000 years ago? Or the one a quarter-million years ago? Or the interglacial a million years ago. And 50 million years ago? 500 million?
Just what are we comparing the present to when we make these sweeping statements?
We just went through an 11-year period 2006 - 2016 with zero cat 3 and above landfalling hurricanes hitting the U.S. Is that our baseline?
None of the coupled climate models had that happening. (Sandy wasn't much more than a giant tropical storm when it made its New Jersey landfall but throw in a landing at daily high tide and the full moon monthly high tide and Chris Christie walks President Obama to re-election)
The thing is, we just don't know what is "normal" and all we can do is hope that our recency bias doesn't lead us into some very dark (literally and politically) places as we feel our way forward.
