cc
I'm Tom Zinnen. I work at the University of Wisconsin-Madison Biotechnology atCenter.b.
I also work for UW Extension
Cooperative Extension. On behalf of those organizations
Wisconsin Public Television, and our other sponsors,
Wisconsin Alumni Association, the Science Alliance here at UW-Madison and PLATO, welcome to
Wednesday Nite at the Lab.
We do this every Wednesday night, 50 times a year. Tonight I'm delighted to be able
to introduce to you Patrick McLaughlin with the Wisconsin Geological and Natural History
Patrick received his master's and his PhD from the University of Cincinnati, finishing up in the spring of 2006.
His focus is on the architecture
of marine rocks in eastern North America.
on the record of hydrosphere, biosphere, lithosphere His research currently focuses
[laughter] interactions; in other words, water, living stuff and rocks.
fashion, here in Wisconsin Especially the Paleozoic rocks, which I interpret to mean really, really old in the metric
and in the surrounding region, and also sedimentary
transport and contamination. ore deposits, and groundwater
I'm not sure, but when I go to the boundary waters and I get to camp on those wonderful,
huge old rocks that are out in
the Canadian Shield, are those the kinds of things you might be talking about tonight?
Those are really old! >> Those are really old.
[laughter] Please enjoy me in welcoming
Patrick to Wednesday Nite at the Lab. [applause]
you. >> Patrick McLaughlin: Thank
It's nice to be here and again thanks for coming out in this fall weather.
As Tom said, I work for the Wisconsin Geological and Natural
from more of us soon. We study the rocks, soil, waters History Survey. It sounds like you'll be hearing
of Wisconsin, and we do that for many reasons, but in part to
help inform policymakers about
environmental issues and hopefully provide them with a bit of context from natural
history.
And so tonight I'm going to talk a little bit about providing
We want to go back one. There we go. some context.
About environmental changes that are happening today and that
are happening fairly rapidly. Today, we are in a state
warming. of global climate change. We are in a state of global
This is a published plot of temperature, average temperature graph some of you may have seen before.
for the northern hemisphere, over the last 1,000 years, and
you can see there's a marked
increase, about 150 years ago, starting with the industrial
temperatures. Why is that? revolution, towards much warmer
community now that greenhouse gases are the primary culprits Well, there's pretty good consensus in the scientific
that are leading toward this warming.
We have CO2 and methane as
two of the major contributors. Notice the C in both of these,
Those are both carbon molecules and the carbon is coming mostly from the burning of organic matter or the transition of
organic matter into a gaseous phase.
human activities. On the lower here, I just added Ita little bit of an artisticnt sorendition of Chicago in theth
summertime, now,
from a Chicago resident. Smog and gas, industrial
are contributing to this activities, just driving cars
build-up of greenhouse gases. >> Can you account for the drop?
There was a drop in the middle
of the 20th century. It's fairly significant.
On this graph, you know, >> Yeah, I don't know.
I really couldn't tell you what is significant and what's not, actually.
But that's a part of the talk,
is kind of assessing, again, gaining some context. What is significant, what's not.
So going forward, you know, what's going to happen
What does this mean for changes in environment and things like is on a lot of people's minds with global warming.
Panel on Climate Change, IPCC, that? We've got the Intergovernmental
and there's various scenarios dhere that are shown in these and assess, firstly, what the warming is going to look like,
They're based on the amount of industrial growth. How much more greenhouse gas is going to be pumped into the
atmosphere is largely going to
little warming in terms of degrees Celsius to three and more degrees Celsius. Now, this model is just based on
anthropogenic delivery of greenhouse gases, industrial
This isn't taking into account activities, and driving cars, and things like that.
other possible natural feedbacks in the system.
mind. So that's kind of where the uncertainty comes in here. So you need to keep that in
There's other folks who are saying right now there's How is this going to go?
a lot of hype about perma frost, melting of perma frost,
that below the arctic ice in the
northern regions there's a lot of methane trapped in perma frost and as the ice melts
it's going to release a lot of
methane. That's not included in this chart.
So there's a lot of side effects
that are potentially involved in this process. And so if we go back and look at
geologic history, we can look at
essentially natural experiments in terms of increase and decrease of greenhouse gases,
and we can look at how that's affected, how that's recorded in the lithosphere, how the lithospheric feedback and
how it's affected the biosphere.
So, what is the end result? One scenario here by NOAA, in terms of precipitation,
trying to model, hey, it's going to get drier here, it's going to get wetter here.
You know, if you have in-laws that live out west, you know, you might want to give them a call, tell them to store some
water.
So anyhow the impact of global warming, when these are modeled,
order assessments, models. these are really kind of first
We know from just the most rudimentary examination of the
temperatures change on the geologic record that when
planet, the climate belts migrate. And that has to do with the way
heat is distributed across the
globe. But essentially as warming
will contract, the tropical belts will expand. occurs, the polar climate belts
But it also, this map actually shows the changes per area
in warming. So there will be a huge change
in parts of the Pacific and parts of Antarctica. in the temperature in the north relative to say smaller changes
will come up, that water Sea level rise, also as those glaciers melt, sea level
has to go somewhere. It pours into the ocean.
Again, if you have relatives Sea level will come up.
living in the Miami or New Orleans area, you might want
How fast is this going to happen? Again, we can model that. There's lots of scientists out
there doing lots of wonderful work looking at the stability of
Wisconsin Geological and Natural ice sheets. We have great scientists at the
History Survey who study the glacial deposits of Wisconsin,
recording the expansion and contraction of glaciers, world class glacial deposits,
especially during the last Wisconsin glaciation that ended
about 10,000 years ago, so we can look at modern glaciers, how
and rock record to try to get an assessment of how they've they're behaving. We can go to the sediment
behaved in the past. And we can go a little bit even
further back in time. Recent, now, you know that geologists, when it says 800,000 years,
that's pretty recent to me. Typically I don't consider
old. things old unless they're a couple hundred million years
There are several records that we can look at to start to
biosphere has changed through time. Carbon 14 you probably heard assess how the climate, how the
It's in charcoal. This is used by archeologists and Indiana Jones all the time about in grade school.
You can date deposits going back to date archeological sites.
cave records. One of the best, really, There are other techniques, speleothems, looking at
is ice cores for assessing how the hydrosphere, the composition
of the atmosphere has changed through time. That record actually goes back
Showing some data here on the bottom of the slide, to about 800,000 years now.
There are ice cores from all this is from the ice core drilled in Antarctica.
over the world now. This one is pretty famous. It's got a very interesting
record. It beautifully shows these kinds
degrees Celsius here, so this is of cycles of rise and fall. Now, this data is represented in
essentially temperature. This is a proxy record, though. You can't just take ice
out of a glacier and say, hey wow, look, temperature. This is essentially, they're
isotopes of hydrogen looking at the different
from the relative abundance of in this case. And we can get into later how do you derive temperature
one stable isotope of hydrogen over another, but it has to do
evaporation of water, transport of water and you can back calculate out a temperature. with the thermodynamics of the
cycles going back in time, So you see these beautiful
so this is going back 400,000 years, and we're sitting here, okay.
So you go back in time and it's about the same temperature and
warm, warm, warm, yes, and then it gets much colder rapidly. then it gets much colder very rapidly, and then it starts to
Or you can go toward the present, which is the typical
way a geologist thinks, and you have rapid warming and then slow cooling and expansion
rapid warming and deglaciation, and then rapid-- of glaciers and then
So there are essentially four or excuse me, growth of glaciers and cooling.
five of those cycles represented here. Now, this is context, okay?
This is what I was talking about
earlier. You say, now here we are today
Is that part of the natural cycle? and it's getting warmer.
Right? I mean, that's been an argument
that people have thrown out there, that, well, it's getting warmer, but sun spot activity changes, and solar insulation,
and things like that. This is probably just part
is saying. of the natural cycle. That's not what this record
And this is, these patterns of warming and cooling, essentially
cycles, they're each about what are known as glacial
100,000 years in duration and there's pretty good evidence that this growth and contraction
of ice sheets, this cooling and warming, is regulated by changes
in solar insulation. Essentially how much of the
sun's energy reaches the earth's
surface. And this is really related--
that only as far as we know occurs when you have large this is a situation, a scenario,
interact with energy from the sun in such a way that they kind ice sheets. So large ice sheets present
of take over, they hijack global climate, okay?
So this warming and cooling,
warming and cooling, this is really telling you about the
sun, that's what's controlling relationship of the earth to the
this, and that's what is causing the expansion and contraction of glaciers.
And so we're sitting here today,
which way should we be going? Should we be getting warmer or cooler?
We're in a warm spot right now. We should be going into the next
according to this record, right? glaciation. It should be getting colder
If we take the last 400,000 years as the norm, then you see these deglaciation,
and warming, and cooling, deglaciation and glacial growth,
going toward the next glaciation. dInstead, we're shooting, to herup this way, okay?ld be
We're getting warmer. And in fact we're getting warmer
than it's been in the last 400,000 years.
So we can't even--
Let me talk about, real quick, about how these records get in the ice.
So the hydrogen record comes
from the ice itself, okay. So you're essentially looking at
isotopes of hydrogen are the record of water and how the
changing in the water that's becoming ice. Another way to get
a temperature is to look at the oxygen isotopes,
they give you an indication both of how much ice there is globally, but also temperature. tThis other graph down here in,
sorry, parts per million, this is a proxy record
for CO2, okay? So you see it matches
the temperature record. And so carbon,
over the last 400,000 years with changes in temperature and changes in ice volume. are marching along in step
ice expands and contracts, And also remember as that
sea level goes up and down. So these are all working in concert.
They're happening at the same time. The oxygen isotope and carbon isotope record is coming from
gas bubbles that are trapped in the ice.
These are little bits of atmosphere that were trapped
at the time that that glacier was growing.
I'm sorry I don't. And glaciers show, I should have a picture of that up here.
oscillations. The banding, the visual banding whas to do with the density bands from summer, winter,
If the glacier is growing rapidly, it has low density, of the ice.
it traps a lot of gas. If it's summertime it's growing
slowly, it's very dense, and it doesn't have a whole lot of gas.
So these records are coming, especially when we're looking at
this record, which is the carbon
These are coming from gas bubbles, bits of atmosphere that dioxide is a proxy from that, or is taken from that.
are actually trapped in the ice. You couldn't ask for anything
better. It's little samples of what the atmosphere composition was
was growing. at the time that that glacier
You go back beyond 800,000 It's a really fantastic record. It gets worse as we go back in time.
years, and there's no more ice record. That's about as old as any
glacier gets on earth.
If we want to look at much longer periods, right, because
a time that's warmer than what I just said we're getting into
we've seen over the last 400,000 or 800,000 years. How do we assess based on even
that long period of time, what to expect, how the earth is going to change and respond
There are all these natural experiments in the rock record. We just need to go look for to ththem.rming?
So we can look at a longer
time period. This is showing the Cenozoic era.
That's 65 million years.
This goes back to the extinction of the dinosaurs, or the age mammals,
you can kind of think of it as. We're looking at two records
So, again, I said oxygen's here. These are oxygen.
a proxy for both ice volume and temperature. This is the oxygen isotope
record going back almost
record. 70 Again, this is the proxynd the beginning of the Cenozoic and the carbon isotope
of the Cenozoic Era actually for carbon dioxide. Now, most or better than half
occurred during a time, the last 30 million years, when there
The Antarctic ice sheet starts were big glaciers on Earth.
to form around 35 million years ago, 38 million years ago. Northern hemisphere ice sheets
start to form around 10 million years ago.
we have big ice sheets. But what we're seeing as So, a good bit of this Cenozoic record is a time when
climate, as global temperature is rapidly increasing,
that our ice sheets are destabilizing rapidly, and
So if we want to understand how the climate system operates tduring a time of ice sheets, we don't have big ice sheets.
time window to look at, the last 30 or so million years. this is probably a good
If we want to understand how that world functions without
ice sheets, we want to go back
further and we can look at the earlier Cenozoic, back in this time interval.
These records come from the shells of tiny, in some cases,
floor. microscopic single celled animals that live on the sea
They're called foraminifera. And so they're sampled from rocks of varying ages to generate this record.
Again, they're a single cell organism that secretes a calcium
essentially. carbonate skeleton to live in,
And, again, that's calcium carbonate,
So those two records it's calcium, carbon and oxygen.
that we want, oxygen, again, this proxy for temperature; and carbon as a proxy
for carbon dioxide
are basic components of those skeletons. What we see around the onset
of the Antarctic ice sheet
is a major shift in the oxygen isotopes. And their shift is associated
with that locking up of large amounts of oxygen in ice sheets.
agreement between this carbon isotope record, which looks relatively straight and flat there's actually a lot of
record. So you take out the ice effect compared to the oxygen isotope
and these start to look very similar.
And it leaves us with a few questions about how temperature and changes in carbon dioxide operate further back in time.
We know from the ice record that carbon dioxide changes during ice house worlds,
called, these times when we have is what it has typically been
carbon dioxide levels tend to track changes in temperature. As glaciers expand, they tend to lock up CO2 and when they
contract they tend to release CO2, and again that's shown in this curve here. There's a slight offset.
It's hard to see. But if you were to overlap those
perfectly, you would see the green is slightly shifted
more toward the modern. CO2 levels track oxygen.
at the Cenozoic as a whole, it becomes a little bit more In some of these older records, especially when we start to look
what that relationship is. difficult, especially at this scale, to assess
Again, so we're looking for proxies on how the world operates and what these
lithosphere, biosphere, hydrosphere interactions are in deeper time, especially during
There's one really interesting greenhouse worlds.
aspect of this carbon record. There's many, but one especially and it's especially pertinent to
our discussion here and that is this little thing right here. That's right at the Paleocene-Eocene boundary.
So these are divisions
of the Cenozoic. Those divisions were made based on the distribution of fossils.
Long before we started pulling
out chemistry from rocks of this age, paleontologists were looking at these rocks and
saying there's a significant
difference between the fossils we find in these rocks down here
In fact, there's a major and the rocks just above them.
extinction of these little foraminifera at that boundary.
also a very rapid change in the carbon isotope values and we see And what we now know is there's
very light carbon introduced very rapidly.
And looking at this and comparing it to the oxygen
isotopes, you see a big spike in oxygen isotopes right here.
So there's a coordinated shift
in the carbon and the oxygen here. And what we've been able to
sleuth out of this, that is,
actually even some scientists working at UW, is that that represents a rapid
introduction of light carbon. That carbon is coming from
methane. That very light carbon
is a signature of methane.
Which is kind of a much more potent form of greenhouse gas than carbon dioxide is.
And this represents a very rapid
rapid warming associated with a release of methane and we're So here we have one example from the Cenozoic of a very
seeing that it was detrimental to life in the ocean as we have
this extinction right here. So that leaves us with some questions.
we see evidence for one rapid warming event. We look at the whole Cenozoic,
How common are these things in the earth's history?
Is this something that happens
all the time and there's some signal locked away in our DNA, in the DNA of the organisms of
the planet to be able to deal with rapid warming, or is this
significant? something totally new and different and especially
How does the carbon cycle operate under greenhouse conditions?
Our best record of how the
carbon cycle operates, which, again, we're carbon-based. All life on the planet is
carbon-based and also those greenhouse gases are
these interactions occur and carbon-based. So if we want to understand how
better constrain our models, we need a better understanding of the carbon cycle, especially
under greenhouse conditions.
And then a kind of question that goes along with that is I've had
that's fine and all, you want to a lot of people say to me, okay,
Isn't there a lot of gaps and look bestuff in there?ic, but Especially as the rocks get older, these 500 million old
rocks you like looking at,
aren't they really, doesn't the record get worse going back? So we can address that as well.
I'm showing here the
earth's history and trying to Gunravel that history frome alooking at those successions.t rockSo to bring us around to of
Wisconsin, the rocks from Wisconsin range from 2.5 billion
that were mentioned earlier, to 350 million years old, those rocks of the U.P.
the Upper Peninsula of Michigan, are in that range of 2.5 billion years old,
an order of magnitude older than
these Paleozoic sedimentary rocks which rim the state. So the Paleozoic rocks are
around as old as 500 million to about 350 million years old.
the Illinois border and up again They wrap around from the Door Peninsula down to
shallow, tropical sea, or several shallow, tropical seas. As you can see, they span an They were deposited in a
So they record a period of immense time period.
Earth's history where we have a fossil record, where we can look at relationships of at least
organisms that had hard parts that can become fossilized and
how they reacted to changes in Earth's climate.
So most of these rocks in the Paleozoic of Wisconsin are
carbonates, okay, like limestone.
I'm sure you're familiar
with limestone or dolostone. We have a lot of dolostone
These are the rock equivalent of in the state.
sediments laid down on the sea floor made up primarily of the
Those organisms for the most hard parts of marine organisms.
So they're creating skeletons. part were secreting their skeletons in equilibrium with sea water.
Where are they getting the material? They're taking it out of the sea
water that they live in.
record of ocean and climate change in an ancient part of encapsulated within them the
Carbon isotope work in Earth's history.
particular in these very ancient rocks has undergone kind of a revolution in the last decade.
Geologists working on the chemistry of these rocks early
on were very slow to embrace looking at the carbon isotopes.
They were worried about modification of the signals.
Were we looking at a robust, repeatable signal?
As I'll show you in a minute, it's incredibly robust. The carbon isotope signal is
both between closely spaced and widely spaced sections. It's a signal that we can incpick up globally in rocksable
of equivalent age.
to look at the carbon cycle It utilizing carbon isotopes.ly do some fantastic work on ancient rocks in terms of trying
carbon isotopes? So you're probably then saying, well, wait a minute, what are
So when we're looking at the carbon isotope record,
of carbon 12 to carbon 13 in those rocks. Those are the two stable we're really comparing the ratio
So why does that matter, and isotopes of carbon.
why does that vary through time? Okay. The way that it varies is that
essentially we're looking at two
different groups of organisms that are affecting the record of carbon or that proportion of
carbon 12 to carbon 13. The first of photo synthesizers that live in the ocean, phytoplankton.
You probably heard that term
before. These are microscopic plants that live typically in the upper
few meters of the ocean.
They're taking the sun's energy and pulling carbon dioxide out of the air and using the sun's
energy to split that and create tissues out of the carbon to
late spring and summertime. Okay? groIt gets warm.te. ThiWe have an abundance ofthe
nutrients.
We get algal blooms. These are the same kind of
living on the surface of that water and they're getting what organisms, single celled plants
Under normal circumstances you they need to grow and they're expanding rapidly.
have the biological pump. This is a recycling mechanism, okay?
So essentially below those algae
So as algae lives, reproduces and dies, eventually it rains ordown into the water column.ng It's attacked by bacteria, which
respire that organic matter,
they break down that organic matter, they take energy from it
respire CO2 just like we do in the presence of oxygen. just like we do and they
So they're pulling oxygen out of the water column.
This is why our lakes, we go
anoxic to a certain degree and then we see these green blue
It's that the abundance of the algae blooms afterwards.
You have all this organic matter algae starts to overwhelm the system. So you have an algal bloom.
that's being created in the surface. The bacteria are trying to break
down all the organics that are
coming in and they're using up the oxygen in the water.
down the biological pump because And when they do that, they shut
they can't exist without oxygen. They certainly can't do their jobs without oxygen.
So that organic matter now
systems. starts to go to the bottom of the lake or the bottom of the ocean in the case of marine
And that's how you get global fractionation from carbon 12 to carbon 13.
The plants are preferentially taking carbon 12 out of the atmosphere because metabolically
They don't want the heavy isotope of carbon, carbon 13, so it's easier to work with.
they're leaving it behind. So in the cases where they die
and rain down onto the surface, they're taking carbon 12 out of the surface and the world becomes enriched in carbon 13.
And this fluctuates back and
forth through time. The other group of organisms are those that are biomineralizing,
those who are creating hard parts from sea water, okay? So they're pulling calcium and
water to create their shells, their skeletons. carbon and oxygen out of the sea
chemistry of that sea water. In doing so, they are encapsulating, essentially the
That is the record we're going for.
fractionation. So one group is causing
The other is just recording that fractionation through time. And those are the guys that we
go after to try and look at changes in the carbon cycle through time. So I'm going to run you through
a case study really quickly.
I've been looking at these rocks of the Silurian Age,
across northeastern America. around 440 million years old,
different than today. ThiThere's a large continentthe sitting over the South Pole Geogrcalled Gondwana.uite
It's essentially South America
and Africa, Antarctica Australia, etc. And straddling the Equator,
you have North America. Wisconsin was a wonderful shallow tropical sea. You've got nearby bits of Europe
as well as Siberia to the north.
The northern part of the world is mostly just a vast ocean.
differences besides the position Again, one of the main
So sea level is much higher than of the landmasses is that the continents all have these shallow seas.
my doctoral studies, the it is today and it's flooding the continents. So I started, after I finished
NSF-funded study, to look at the Silurian Age rocks across eastern North America,
essentially from the
And the rocks in the east are different than they are here Maryland area, to essentially Wisconsin.
in terms of their lithology, in terms of what rock types
are there.
They're mostly shale. This is essentially like compressed mud and sandstone and
minor components of limestone.
They're exposed at the surface in places, and they are penetrated by borings into the
subsurface that are housed at the various state Geological
where those data points are. Surveys around the eastern U.S. And this is just showing
There are general kinds of belts where the Silurian rocks are
They're mostly shale through mostly sand over in this area.
this area, and there's a lot of limestone and associated lithologies in this area.
That's telling us during the
Silurian, this was a deposital basin.
There were mountains off this way, and this was kind of a catchment area for sediments.
So what I'm showing here
is a cross-section. This is across Ohio, essentially from the margin of that basin,
the western margin of that
that are constrained, in part, basin, going out into the basin interior. These lines represent timelines
a lithologic log or a log of by the carbon isotope values, which are these profiles here for each one, and then there's
the changes in the composition the different rock types that's associated with that. So the study is looking both at
of the rocks, as well as the chemistry of the rocks. When you put all that together,
you end up with essentially a slice across that basin that looks like this. So this is for a specific part
of the Silurian.
Again, this is a time about 440 million years ago. This is a basin fill.
These are marine rocks. They're full of fossils and things like that. What it's showing us, the
take-home message here is that
this basin had very little organic carbon deposited in it
All these red and green colors, these are telling you that you for several million years, okay?
but very little carbon. When you have high carbon level hain the rocks, it masks theses of iron present in the rocks,
gray to black, okay? colors and you get shades of
And that's indeed what you see up here.
we have a change in the lithology and that's reflecting the carbon content. SoSo we have a period, a longis
period, this initial basin fill,
that has very little carbon and then an abrupt change to a lot of carbon being deposited in
this basin. When we look at the carbon
mostly with a time when we had isotope profile, that time of low carbon fill is associated
It's warm. very low carbon isotope values. Essentially it's telling us we're in a greenhouse period.
There's a lot of carbon dioxide. When the values shift in this direction, we see suddenly that
we have lots of organic carbon
the carbon cycle essentially in the rocks. This is telling us that even if you go back 400+ million years,
surface ocean and you put it in the bottom and that causes that global ratio of carbon 12 to You take organic matter from the
That's the take-home carbon 13 to shift.
right there. The red and green rocks had very little carbon.
There was essentially no net
flux of photosynthetic light carbon or plant remains, if you want to think of it that way,
to the bottom.
The biologic pump was working, everything was being recycled,
that ratio globally of carbon 12 there was very little change in
matter made at the surface, it went to the sea floor and Suddenly something happened and there was a lot of organic
continued to do so for a good, long time, and that causes the
rocks to turn gray to black,
like old graphite in a pencil, it has that gray to black color.
It changes the color of the rocks like that. That's carbon.
values that indicate that globally you're having a period And it of carbon burial.dinated sThe two reinforce each other.o
They're telling us that the carbon cycle is working as it does today, essentially.
The interesting thing is this is And that's reassuring.
associated with one of the largest mass extinctions
time period. in that time, in the Silurian
So a bunch of organisms go extinct right around that time. So that's telling us that, wow,
something happened. It changed that carbon cycle
dynamic. And that was not a good thing
for most life on Earth. It's also associated with a major fall in sea level and some
get into in a minute. And, again, this is not just -- these patterns we don't just see other changes as well that I'll
this is a globally synchronous in eastern North America, but
event. We can look at those same rock
and we see the same patterns. So just to summarize what our study showed is that these are records on different continents
There's a little blip down here. the carbon isotope values.
around the same time. We have some oxygen isotope data with sea level over here, sea level dropping and then rising
as well, which is indicating a shift towards cooler
temperatures associated with
that little blip. The big change that I just showed in that diagram is in
this interval, where we see a large shift in the carbon isotopes, a major cooling and evidence actually for glacial
deposits in South America,
what is today South America, and a big drop in sea level.
we see in the ice core record. So this is very similar to what
The difference is, and it's a subtle difference, is in the offset between the carbon
isotopes and the oxygen isotopes. During the ice house world, the carbon isotopes
or carbon dioxide tracks temperature change.
dioxide. So it gets warmer, glaciers contract, you release carbon
Silurian and as it will turn out And then the reverse is true as well. In the greenhouse world of the
other time periods as well, it's just the reverse. Carbon dioxide, changes in
carbon dioxide, are forcing changes in temperature, okay? So those greenhouse gases are forcing, in a greenhouse world
that's the primary control on temperature, is the flux of greenhouse gases, okay? Increase greenhouse gases,
it gets warmer. Decrease them, it gets cooler.
To bring it back to Wisconsin, There's a pretty direct relationship there.
we've got some beautiful data from Wisconsin that matches very well, both that data from over
in the Ohio River Valley, as well as kind of
period, but it's a fantastic what the global curve is. This is for a longer time
tool. Not only does it tell us about the carbon cycle.
It's allowing us to align these geologic records from all over
the world in a much more accurate way.
We've also looked at some older rocks in pretty fine detail, and
this is just a quick summary slide to say similar patterns
exist in even the older rock, so the Silurian are some of the youngest Paleozoic rocks
Even the older rocks show similar patterns. There are high frequency in Wisconsin.
This is a large, in the heavy gray line this is a large shift in the carbon isotope values patterns.
There's a high frequency signal there as well and there's some for some of the older rocks.
really large negative excursions in there.
This is still pretty preliminary
work, but it looks very similar to the Paleocene-Eocene boundary that I talked about the
Cenozoic. So we've got some evidence for
very rapid warming events in the record as well and we have some
volcanic ash beds in there that help us constrain the duration
of those things. So kind of to summarize, we're
trying to kind of pull together these ancient rock records to get a better sense of how the carbon cycle operates during
greenhouse times and what some
in or out of the hydrosphere. So this is showing essentially, wheI'm sure you've never seenge the flux of greenhouse gases
This is a cross-section from anything like this before.
Wisconsin, from essentially Madison to Virginia. And the Y axis here is time.
So this is the whole Silurian period from about 440 million years to 415 million years, getting younger towards the top,
and these are the rocks that are
preserved today. We've just kind of reconstructed
ages. And the take-home message from them in terms of their different
this reconstruction is every time we get big shifts in the
carbon isotopes, we're seeing coordinated shifts in evidence
for sea level fluctuation, carbon burial, extinction.
They all go hand in hand
over and over again. There are multiple, large changes in the carbon cycle and
we see that pattern repeatedly. We can go to slightly older rocks.
So now we're looking at 480 to 440 million years. It's the same pattern These over and over again.ocks.
We can look at even older rocks in Wisconsin. And part of the work is really
record with the carbon isotope trying to tie in the fossil
It's not a plant, wasn't record. This is showing the diversity of a planktonic organism.
Its organic remains are found in an algae, it's long extinct called a graptolite animal. This is the critter up here.
a lot of fine grain rocks of order of issue of Silurian age. This pattern down here
is essentially showing its
diversity through time. So these things were kind of prolific during certain times
and became very diverse and then
through the early part of the thOrdovician, and this reallyt. parallels a global trend that we run-up to very high diversity
called the Ordovician radiation. see in the Ordovician that's
This is one you should teach your grandchildren. This is essentially the
diversification of life on the
You've probably heard of the planet as we know it. This is where all the animals came from, okay?
Cambrian explosion. That's the appearance of a lot of weird things that went
extinct pretty fast.
Even though not the same The Ordovician radiation is the appearance of all the forms that we essentially see today.
species, the major families. So that happens during this time.
We look at the carbon record
and it's pretty quiet. This is actually, this is a greenhouse time and there's not
a whole lot going on. When we start to see the carbon isotope record or the fluctuations in carbon dioxide,
we can think about it.
When we start to see that really vary, that's when this record of
record of life, really starts to graptolites or a proxy for the
get ragged and we see some very abrupt changes and we can look at this in a different way.
This is a plot of extinction
intensity. This is from a recent paper in
fossil record was plotted against, and that would be here, "nature," where essentially the
550 million years old on this end to the present, and this is how much extinction is going on. So this is rocks that are about
These are essentially mass extinction events. The rocks of Wisconsin, the APaleozoic rocks, occupy abouts.
this period of time, and you can
see we have multiple major extinction events captured in that rock record.
And they're all coincident with major changes in the carbon isotope record. So just to wrap it up then,
global warming is happening today.
environmental and societal Absolutely. It's causing significant
changes. To really put it in context,
of how climate has changed in the past. Definitely especially for those tforward models that we reallye
need a better understanding of
the behavior of the carbon cycle, especially under greenhouse conditions.
We have these ancient records like in Wisconsin.
carbon isotope pattern. They show direct changes They show a direct relationship between carbon burial and the
And there are also these little negative excursions in there associated with changes in sea level.
as well that look very much like this, the Paleocene-Eocene
thermal where they have this
very rapid warming. Peaks in extinction rates seem to be tied very closely with
rapid changes in the carbon cycle and that's ongoing work that we're continuing to focus on.
So I thank you for your time. [APPLAUSE]