Welcome to Meteorology Matters. Ever wonder about
the history of hurricanes in the Caribbean? I
mean, way back, even further than our records
go. Yeah, that's a great question because the
Caribbean is, you know, it's been a hotbed of
hurricane activity for, well, for as long as
we've been keeping track, really. Exactly. But
today we're going to dive into some really cool
research that takes us back thousands of years.
Thousands, yeah, way back, 5 ,700 years, to be
exact. Wow, that's before the pyramids. So how
is that even possible? I mean, our weather records
only go back a couple of centuries at most, right?
Right. Like, our good instrumental data only
goes back about 73 years. And historical accounts,
maybe like 173 years. So how do we jump from
that to 5 ,700 years? What's the secret? The
secret's actually hidden in plain sight. It's
the Great Blue Hole. The Great Blue Hole. You
mean that incredible natural wonder off the coast
of Belize? The one that Jacques Cousteau made
famous? The one and only. It turns out it's not
just a stunning diving spot, it's also a time
capsule for hurricane history. So we're talking
like a giant sediment core. Exactly. A 30 meter
long core that gives us a year by year record
of storm activity. Wow. So each layer of that
sediment is like a page from a hurricane diary.
That's way beyond anything we had before. You
mentioned 2 ,000 years was the furthest back
scientists had looked. Right. Even the best studies
before this one only got us back about 2 ,000
years. So this new data more than doubles our
understanding. Incredible. But before we go any
further, can we back up a sec? I'm still wrapping
my head around this. How exactly does a sinkhole
record Oh, sure. So the Great Blue Hole sits
on Lighthouse Reef, right? And because of its
location and the way sediment settles in it,
it's super sensitive to any tropical cyclone
that passes by. OK, so when a hurricane hits?
Exactly. When a hurricane hits, it stirs up all
this sediment and debris from the reef and the
coastline. All that heavier stuff gets washed
into the Blue Hole, which is relatively calm,
and it settles down in layers. So each hurricane
leaves its own unique fingerprint in the sediment.
Exactly. And those fingerprints, they add up
over time. creating this incredible record. Okay
so now we have this 5 ,700 year record. What
is it actually telling us? What's the big picture
when it comes to Caribbean hurricanes over that
time span? Well the main takeaway is that there's
been a clear trend of increasing storminess in
the southwestern Caribbean over those millennia.
So basically more hurricanes over time? Yeah
like a slow but steady increase in the number
of hurricanes over thousands of years. Wow. But
what's causing that? I mean, that's a seriously
long -term trend. Is it just random chance? That's
where it gets really interesting. The researchers
link this increase to changes in Earth's orbit.
Wait, hold on. You're saying the way our planet
moves around the sun affects hurricane activity
in the Caribbean. Absolutely. It's about the
Intertropical Convergence Zone, or ITCZ for short.
It's this belt of clouds and rain near the equator.
You see, over thousands of years, subtle shifts
in Earth's toot and wobble, we call those, obliquity
and precession, affect how much solar radiation
different parts of the tropics get. That, in
turn, influences where the ITCZ sits. It's like
this really slow but powerful steering wheel
for global weather. OK, so if this ITCZ moves,
what happens to hurricanes? Well, the main breeding
ground for Atlantic hurricanes is closely tied
to the northern edge of the ITCZ. Ah, so as the
ITCZ shifted south over time. Bingo. that prime
hurricane -forming zone also shifted south. And
that means more storms were likely to end up
in the southwestern Caribbean. That's amazing.
So it's like this cosmic dance between Earth's
orbit and hurricane pathways playing out over
millennia. You mentioned that records from Puerto
Rico show a similar trend to Belize, so this
is happening over a large area. But you also
said that this increase in storminess isn't uniform
across the entire Atlantic. What's up with that?
It's super important to remember that. While
Belize and Puerto Rico, being at similar latitudes,
show this clear upward trend in hurricanes, places
further north, like Florida and the Bahamas,
tell a different story. How so? Well, over the
same 5 ,700 years, their records either show
more stable hurricane activity or even a slight
decrease. So the Caribbean is getting hit more,
but other places maybe not so much. That suggests
that something more complex is going on than
just a general warming of the Atlantic Ocean,
right? You got it. It's not just the overall
Atlantic sea surface temperature that matters.
It's also these large scale atmospheric patterns
driven by things like the ITCZ that really influence
where hurricanes form and where they go. That's
a great point. So we've been talking about these
really long term trends spanning thousands of
years. But what about shorter term fluctuations
like those happening over decades or centuries?
Do the researchers find anything interesting
there? Oh, absolutely. On top of that long term
increase, there are these shorter -term swings
in hurricane activity. And they seem to line
up with known climate periods during the Holocene
Epoch, which is roughly the last 11 ,700 years.
So basically it's not just those massive orbital
shifts that matter. Other climate factors can
also make a difference in how many hurricanes
we see over shorter periods. Yeah, exactly. Things
like variations in how much solar energy is hitting
Earth. which affects sea surface temperatures
and different modes of climate variability all
likely play a role in these shorter -term changes
in storminess. Can you give an example of how
these shorter -term climate factors have affected
Caribbean hurricanes in the past? Sure, let's
look at the last 1200 years. The Great Blue Hole
record matches up really well with the overall
hurricane activity across the whole Atlantic
basin, as well as a regional record from the
Yucatan Peninsula. For example, during the medieval
warm period, a time when global temperatures
were generally warmer, both the Great Blue Hole
and the wider Atlantic saw more hurricanes. But
then during the Little Ice Age, which was a cooler
period, hurricane activity in both the southwestern
Caribbean and the entire Atlantic tended to drop.
Fascinating. So it seems like factors like solar
activity and these large -scale climate oscillations
have a real impact on how many hurricanes form
not just over thousands of years but also over
shorter time frames. So all this talk about past
hurricanes is really interesting but what does
it tell us with the future? Especially with all
the concerns about climate change. I mean is
the Caribbean in for even more hurricanes as
the planet keeps warming? That's the million
dollar question, and the researchers did tackle
that. They looked at the recent high levels of
hurricane activity in the southwestern Caribbean
and made a projection for the 21st century. And
what did they find? Well, their projection suggests
that we might see a huge increase in hurricanes,
maybe even an unprecedented increase. Unprecedented.
That sounds pretty serious. What's driving that
projection? The main factor is what we've all
been talking about, global warming. As temperatures
climb, the sea surface temperatures in the main
hurricane development region are getting exceptionally
warm. And as we know, warm water is like rocket
fuel for hurricanes. So warmer oceans, more hurricanes.
Makes sense. Anything else feeding into this
projection? Yeah, the National Oceanic Atmosphere
Administration, NOAA, predicts that tropical
Atlantic sea surface temperatures will keep rising
over the next few decades. Plus, they're expecting
more frequent La Niña events, and historically,
those tend to boost hurricane activity in the
Atlantic. Hmm, so it sounds like a perfect storm,
so to speak, of factors that could lead to a
lot more hurricanes. It does seem that way. Their
worst -case scenario estimates something like
45 hurricane strikes in the southwestern Caribbean
between 2000 and 2100. Forty -five. Wow. That's
a lot. And how does that compare to the natural
variations we've seen in the past? It's much
higher than anything we've seen in the Holocene,
even during those periods of increased activity
we talked about earlier. That's sobering. But
I'm curious, did the researchers explore any
other possible scenarios, maybe ones that aren't
quite as dire? They did. One alternative scenario
involves a more dramatic warming in the northern
Atlantic compared to the tropics. This could
shift hurricane tracks and those zones where
hurricanes reach their peak intensity further
north. So basically, hurricanes might bypass
the Caribbean and head north instead. It's possible.
In that case, the southwestern Caribbean might
actually see a decrease in hurricanes. However,
that would likely mean more hurricanes, maybe
even stronger ones, hitting the northern Atlantic.
So it's a trade -off. Right. So no matter what,
it seems like we're in for some significant changes.
You know, this whole discussion has really highlighted
just how valuable this great blue hole record
is. But I'm curious, how did the scientists actually
get all this information about ancient hurricanes
from that sediment core? What were the key techniques
they used? It's a really impressive process involving
what's called a multiproxy approach. The first
step was looking for visually distinct event
layers in the core. You mean layers that look
different from the normal sediment. Exactly.
These layers often have a different color, and
they lack that fine annual layering, the lamination
that you see in sediment that's deposited under
calm conditions. So these visually different
layers are like the first clue. Got it. So...
What other evidence did they look for to confirm
that these layers really were from hurricanes?
Well next they did a careful analysis of the
sediment's texture, looking at grain size. Hurricane
layers typically have coarser stuff like sand
and gravel, often even bits of shell and coral
that were ripped up by the storm surge. Right,
so those heavier materials would get carried
into the blue hole by the storm waves? Did they
measure anything specific about the grain size?
Yeah, they measured the average grain size and
the percentage of this coarser material in each
layer. These different proxies, the visual appearance,
the grain size, each tell part of the story.
And by putting them together, they get a much
clearer picture than they would from just one.
That makes sense. It's like having multiple witnesses
to confirm the same event. Was there any chemical
analysis involved as well? Oh yeah, they looked
at the ratio of strontium to calcium in the sediment.
Higher ratios of strontium usually mean more
reef material was washed into the blue hole during
storms. Reefs tend to be richer in strontium,
so that's another sign of a hurricane. And do
they use any other techniques? They also used
gray stale analysis. Basically, they took x -ray
images of the core and variations in the shades
of gray reflect changes in the sediment's density.
Storm layers often have a unique density signature
compared to the surrounding sediment. Wow, so
they really threw the whole scientific toolbox
at this, huh? So they have these visual clues,
grain size data, chemical analysis, even density
measurements, all pointing to past hurricanes.
Exactly. It's a very thorough approach. Makes
sense. But how do we know this record actually
goes back 5 ,700 years with that impressive annual
resolution you mentioned? How did they figure
out the timeline for all these hurricane layers?
Well, for the annual resolution, they mainly
relied on counting varves, those annual sediment
layers I mentioned. But to be extra sure, they
also used radiocarbon dating at different depths
throughout the core. So carbon dating to double
check the age of the sediment, that's pretty
standard. But were there any other methods they
used for confirming the timeline? Yeah, they
used a few other clever tricks. For example,
they looked for pollen from plants linked to
human agriculture. Those show up at known historical
periods and can be used as timestamps. They even
found ash from the 1982 eruption of El Chichon
volcano. It acts like a time marker, helping
confirm the accuracy of their timeline. By combining
all these different dating techniques, they could
be confident in the age and that yearly detail
of this amazing record. It's like a historical
jigsaw puzzle, and they found all the pieces.
But one last question. How do we know for sure
that these layers really represent hurricanes
and not just some other random disturbances in
the ocean? I mean, could it have been something
else that stirred up the sediment? That's a great
question. To check the reliability of their findings,
they compared the top part of the core, the most
recent sediment, with actual hurricane records.
from 1950 to 2022. And guess what? There was
a really strong match, with something like 84
% of the storms that passed near the Blue Hole
being recorded in the sediment. 84%. That's pretty
convincing. So it's safe to say that most of
those layers throughout the core are accurate
records of past hurricanes. Yeah, it gives them
a lot of confidence in their data. They even
found that hurricanes approaching from the south
were more likely to be recorded than those from
the north, likely because of the shape and position
of the Blue Hole. There were a couple of layers
that didn't perfectly align with known hurricanes
and they think those might be from other events
like intense winter storms or even distant earthquakes.
But the vast majority line up really well with
the historical hurricane record. That's some
amazing detective work. So as we wrap up, what
are the big takeaways from this 5 ,700 year hurricane
record? What can our listeners learn from this
peek into the deep past? I think the biggest
lesson is that hurricane activity in the Caribbean
is influenced by so many factors, from these
slow grand shifts in Earth's orbit to shorter
term climate cycles and even human caused climate
change. It really shows how interconnected everything
is, right? From the movement of our planet to
the intensity of storms and even the future risks
for people living in hurricane prone areas. Exactly.
And it's a reminder that understanding the past
can help us better prepare for the future. Absolutely.
The fact that a sinkhole can hold such a detailed
and long -lasting record of these powerful events
is just mind -blowing. If you found this exploration
of past hurricanes intriguing, be sure to follow
meteorologist Rob Jones on Instagram, Meteorologist,
on TikTok, TV Meteorologist, and on YouTube,
follow Rob Jones Hurricane, where you can also
find the Meteorology Matters podcast playlist.
There's always more to learn about the forces
that shape our weather. Until next time, keep
exploring the world around you.