cc  >> Welcome everyone to Wednesday  Nite at the Lab here at the  UW Madison Biotechnology Center.  Tonight's topic will be from  Ian Orland who is currently  a graduate student in geology  and geophysics.  He's originally from Illinois  and he just finished his masters  degree.  And he's going to be telling us  about his research on using  geology to look at ancient  climate change and its effects  on previous cultures.  So join me in welcoming  Ian Orland.  [APPLAUSE]  >> All right, thanks very much  to my host for having me here.  It's an honor.  Hopefully, I can live up to some  of the great topics that you  guys have heard about in past  weeks.  So to start I'll start with a  brief outline of how I hope this  talk is going to go.  We'll start with just a general  interest, why the public is  interested in global warming. 

 And then, in the context of  that, how we get, how geologic  records play a role in  understanding both future and  past climate change.  And I'll give some examples of  marine, polar and terrestrial  records of climate change.  And then, in terms of this big  picture view, I'm going to try  and explain where the research  that I've been doing in the  Department of Geology fits into  this and specifically my study  of high resolution analysis of a  Sorek Cave stalagmite.  So on we go.  Okay, so first, climate change,  why do we care?  There's been a lot of attention  in the media to something called  global warming and most people  understand this, but I'll just  give a brief background.  A lot of the interest stems from  this figure where we're plotting  for the last 1,000 years of  earth's history the  concentration of CO2 in the  atmosphere, which is that blue  curve on the bottom there.  And that's on the right hand  axis.  And you can see in the last 200  years atmospheric levels of CO2  have increased greatly.  And the black curve there also  plotted for the last thousand  years is showing northern  hemisphere temperature anomaly.  So you can see over the course  of the past hundred years or so,  kind of in concert with the  increase of CO2 concentration,  northern hemisphere temperatures  have increased dramatically  compared to the changes that  we've seen over the last  thousand years. 

 So, of course, this is  interesting and has led to a lot  of study in climate science in  the past 20-30 years.  And where is this going?  Here is another reason that  people are interested in  studying climate.  This figure and the last one  were both from a study put out  by the Intergovernmental Panel  on Climate Change which is put  together by the UN,  in I think 1988.  And they put out a study every  six years or so to say kind of  where the state of the science  is and what we know about past  climate change and what that  tells us about future climate  change.  So the graph on the left is now  showing projections 100 years in  the future of those CO2 levels,  the blue curve in the last  graph.  And so you can see that for  sort of five or six different  scenarios of different political  situations and energy use  whether or not we sort of moved  away from fossil fuels as a form  of energy.  They've got different models  there on the left hand side  showing how much carbon dioxide  we're going to put into the  atmosphere over the next hundred  years.  Each of those colored curves is  then represented in the graph on  the right hand side where you  can see plotted global surface  temperatures on the vertical  axis versus time and we go from  the year 1900 to 2100.  So the black line shows where  we've been in the last 100  years, and then all of those  colored lines correspond to  those CO2 models on the left, so  we can see in the next hundred  years what kind of warming  we might expect.  And, of course, there are error  bars on each of these  predictions based on factors in  the global climate models. 

 And I'm not going to try and  convince you in this talk  whether or not global warming is  caused by humans.  But I would recommend, if you're  interested in this, coming to  the talk next week.  Michael Notaro knows a lot more  about these global climate  models than I do and will be a  great resource to find out more  about that.  And I should also mention the  IPCC who puts out these figures  has a great web site down there  at the bottom and if you're  interested in learning more on  this topic I highly recommend  you going there.  You can get all of these images  and a lot of interesting reading  material.  So after looking at those  last plots, some questions.  Where do these past climate data  come from?  How do we know what temperature  was like even a thousand years  ago?  And another question, how are  these climate models, that are  used to predict the future, how  are they tested and calibrated?  How do we know that they're any  good?  So we're going to approach these  one at a time.  And just briefly an answer to  the first one, where do these  data come from?  They come from multiple proxy  type records of climate change.  And those can range in type from  instrumental, so just reading a  thermometer and writing it down  and you can go back and look at  these historical records.  Or biological, so for instance,  tree rings, many of you have  probably heard of those as used  to interpret past temperature. 

 And there are also quite a few  geologic records, and I'll get  into those in a minute here.  So if we go back and think about  that first temperature curve,  it turns out it's not as simple  as just one single black line.  There is a lot of different data  that's gone into this.  It's not just a single proxy.  Many different scientists have  looked at this.  So we've got the exact same plot  here.  So the last 1,000 years versus  temperature change, and this is  what's known as the hockey stick  curve.  And it was, the data was put  together by a scientist by the  name of Mann who's out of  Penn State University.  And so you can see here his plot  that we looked at in the first  slide is that dark blue line  that runs across there.  But there are many other  studies. 

 The green and yellow lines are  based on tree ring studies, as  well as ice cores and other sort  of terrestrial sediment records,  as well as the black line in  there.  And you can see that depending  on what records you use and how  you calibrate them they can give  you slightly different answers.  But the idea is all together  these trends can tell us some  very important information.  And the other thing to note is,  obviously, the instrumental  records of reading a thermometer  only goes back so far.  So that red line all the way on  the right side only goes back  150 years or so.  So we clearly need some other  way to interpret climate from  the past.  So this is the hockey stick  curve and you'll probably hear a  lot about that in the news.  And so here are some other  records of climate change.  I mentioned the instrumental  record and using tree rings.   And so what I've got plotted  here is on the horizontal axis,  it's at the top there, it's a  logarithmic scale of the time  span of the record, so the  usefulness of the record. 

 So for instance, the  instrumental record goes from  modern day all the way back to  ten squared years, so 100 years  and on down the list.  So tree rings are good for about  1,000 to 10,000 years.  Of course, you can see there are  many other records and the ones  that I've got highlighted with  the red arrows are the geologic  records that I'm going to focus  on here today.  So there are many different  types of records and they are  useful for different things.  So for instance, the records  that are sort of plotting  towards the right of this figure  are very good at giving us high  resolution records of climate  change.  Whereas, records towards the  left are important for  projecting back hundreds of  thousands even millions of years  so we can tell more about the  past.  So I kind of got into this but  the other question we asked  initially is how are these  climate models tested and  calibrated?  Well, we compare them to  observed climate data in the  past.  So if we have to understand the  past to know where were going,  the idea is that if you know in  the past there was some climate  perturbation, if you apply that  forcing to your model and your  model doesn't give you the same  or the correct results that you  would expect then you might have  a problem with your model.  But if your model gives you a  similar response in the climate  according to what forcing you  put in, then you know you might  be on the right track.  So this understanding past  records of climates is very  important for adjusting the  models that we use for the  future. 

 So that's kind of a big picture  overview of why climate  scientists are interested in  these records of past climate  change.  So now on to a couple of those  records I was talking about.  First type that many people have  heard about is polar ice cores.  And so these are vertical cores  that are taken in spots where  ice caps, so for instance, on  Greenland and Antarctica, are  very thick.  And these cores can be up to  three and quarter kilometers  long, continuous.  And the picture on the right  shows a couple of guys that are  pulling out, piece by piece of  course, three and a half or  three and a quarter kilometers  worth of ice.  This takes many, many years.  You can only be in these  extremely cold regions for so  many weeks out of the year.  And the figure on the left shows  the altitude, or sorry, the  surface elevation of the  Greenland ice cap.  And down at the bottom there's a  little cross section, and I've  plotted there in red in the  cross section what one of these  ice cores would look like. 

 So they traverse the entire  3-kilometer height of the ice.  And of course these are put down  in layers so the oldest ice is  at the bottom and the youngest  ice is at the top.  And the ice caps kind of act  like pancake batter.  They spread out as they get old.  So you pile more and more new  ice or new batter on top and it  compresses and kind of smears  out on the edges.  And so this means that the  layers at the top, when you put  down an annual layer, are much  thicker than the layers at the  bottom.  And that has implications for  layer counting and understanding  what the resolution of your  record is.  The other interesting thing  about these ice core records is  not only does the water  chemistry in the ice tell us  something about past climate but  there are also trapped gas  bubbles from ancient atmospheres  within the ice.  And so as the ice cap grows  vertically, the ice traps these  bubbles of old atmosphere and  you can put a needle in there  essentially and pull out an  atmosphere sample that is 50,000  years old and you can say how  much CO2 was in the atmosphere  then and we can compare that to  today and we can look at  patterns through time.  So there's some very interesting  work that's being done in ice  cores. 

 Now I've got a picture here at  top that shows the annual layers  and the top kilometer I think or  so these annual layers are  fairly clearly identified so you  can actually count and have a  record that's accurate to within  a handful of years depending on  how good you are at counting  50,000 or 10,000 layers.  And then at the bottom I've got  locations of some of these ice  cores in the north and near the  north and south poles.  Now interestingly enough, the UW  actually has quite a history in  the Antarctic and there's a UW  Polar Research Center that was  started in the late 1950s and  ran through the 1990s, and  there's a group of them up there  on the top right looking rather  cold.  I guess a comfortable day is  something like minus 60.  Something crazy like this.  And then on the left all these  places you may not be able to  read all of them.  Those are all actually geologic  features, like mountains or  valleys, that are named after UW  professors and staff that did  work down there.  So that's pretty interesting.  Another famous alum of the  geology department here at UW is  a man by the name of Richard  Alley who did his doctoral work  in the department.  And he's actually gone on to do  a lot of important work with ice  cores. 

 He worked a lot in Greenland,  and he's written this fairly  well known book called The  Two-Mile Time Machine which is  another very interesting read  sort of for the general public  in understanding how these  records come to be and what they  mean.  So I recommend checking that out  also if you haven't already.  So here's kind of a summary plot  of some of the data you can  obtain from ice cores.  And at the bottom there in the  black, that's actually water  chemistry data for the last  600,000 years, you can see on  the horizontal axis at the  bottom there.  So you can see there are  interesting patterns of  cyclicity.  There's a hundred thousand year  cycle in there and there are  some other interesting things on  short time scales that are of  note.  I won't get into too much  detail.  The top three curves there, the  green, red and blue curves, are  all from those trapped gas  bubbles.  So you can see that, as well as  the water chemistry, the trapped  gas bubbles are also showing  some interesting patterns of  cyclicity.  You can see that hundred  thousand cycle in there as well. 

 Just of note before I move on,  those three little colored stars  in the top right corner, while  we thinking about future climate  change, those are actually to  scale with the data that's  plotted there.  So for instance, the green star  in the top right is on the same  scale that all the green curve  is plotted on.  The red curve is actually CO2.  So you can see that for the past  600,000 years CO2 has been  varying in some kind of regular  pattern and then all of sudden  the current atmospheric level is  almost, it's well off the scale  there.  So this is something to think  about as we talk about  temperature change on the globe  when we compare it to past  records there are some  interesting correlations that he  we can think about here.  Of course one draw back of these  ice core records is that for the  most part you are limited to  interpreting climate from polar  regions.  There are a few mountain tops  where people have come up with  extended records.  But what about the low  latitudes.  What about the oceans where most  people live.  One alternative in geology is to  look at marine sediments and  these are sort of similar to an  ice core. 

 There are living creatures and  weather products that come off  the continents that settle down  in the ocean.  So these are deposited through  time.  So again at the bottom of these  cores you have very old  material.  At the top you have much younger  material.  So these drill ships will go out  into the middle of the ocean and  put down drilling strings and  bring up these hundreds of  meters worth of core and this is  a useful proxy, as well, for  looking at past climate.  In fact, some of those  microorganisms that live in the  ocean and as they die they rain  out, they record interesting  things about, for instance, past  sea surface temperatures.  Or past, the size of the ice  caps on the north and south  pole.  Those kinds of information are  recorded in the microfossils  that these microorganisms live  behind.  So you can go to a core and pull  one of these microfossils out  and construct a section going  back in time.  Just for scale here, the picture  on the left is a microscope  image of a foraminifera, that's  what those little creatures are  called, inside the eye of a  needle. 

 So they're pretty tiny.  To measure these things easily  we have it spend a lot of time  on the microscope picking them  out of a sediment and then to  analyze them generally you  gather a group of them and  analyze the shells all at the  same time.  And that will give you a  geochemical data point, and you  have to do this many, many times  all throughout your core to  create a record that goes back  thousands of years, for  instance.  And there are different species  like I mentioned before.  Some live in shallow water and  some live in deep water and  those can tell you differing  things about what's going on in  the ocean.  And all these little spots, some  of them are hard to see,  indicate where the coring has  been done.  So you can see all across the  oceans at mid-latitudes these  records have been constructed.  And when you combine these  records together and line them  up with each other, just like  with the ice cores you can  create records that are 600,000,  even millions of years old that  tell us about the chemistry of  the ocean and the climate.  So here's a record showing, this  proxy is useful for showing  temperature and polar ice cap  size change through time.  So if we stack these all  together, the top four being  those ice core records and the  bottom being from the  foraminifera, you can see that  there are some very interesting  trends again that pop out. 

 So these global climate changes  are being recorded not only in  marine sediments but also in  polar ice cores.  And as I hope to show you,  they're being recorded in other  places in the geologic record,  as well.  So now that we've looked at  polar regions and oceans, what  about the continents.  So for instance, in North  America or in Europe, how can we  tell about past climate on the  continents?  Well, there are a couple of ways  and just briefly one way that  many, there's actually quite a  few people at the University of  Wisconsin that study this is  using a similar coring to the  oceans but now you do it in  lakes.  So people have done this all  over North America.  You take a core from a lake and  you can pull out pollen from  trees and flowering plants that  has collected in the lake and  settled down.  So you can create a pollen  record through time.  Down on the left here I've just  gotten an example from a recent  paper from a UW professor.  13,000 years ago climate in  North America got almost 10  degrees cooler in some places  and, as a result, in these lake  pollen records, you can see on  the right there that the  non-arboreal pollen, which are  like grasses and so on, change  dramatically.  So you can start to tell things  about climate change based on  the abundance of what types of  pollen are in these lake bottom  sediments. 

 And as well as for just one  single place, you can of course  compare many different lake  cores from all over North  America and start building some  spatial relationships.  So through time how did eastern  or western North America change  from 20,000 years ago when the  last ice age was in full swing  to today when it's much warmer.  You can see the distribution of  plants changing and so on.  And finally now we're getting  towards what I study,  stalagmites, which are also  known as speleothems in jargon  speak.  So stalagmites can also be used  to tell something about past  climate, and the thinking on  this is very similar to tree  rings in that if you imagine a  stalagmite, I've got an image  here on the left from Carlsbad  Caverns, and you slice it just  where that red line is,  obviously we wouldn't do it to a  beautiful formation like this.  But if you slice it and look at  a stalagmite in cross section,  you get something like the image  on the right there where you  have many concentric rings,  where the oldest growth rings  are in the center and the  youngest growth rings are on the  outside.  So the idea that if you do some  geochemical analysis from the  center to the edge of this  stalagmite you maybe able to  walk back in time just like in a  tree ring and tell something  about temperature or rainfall  amounts.  And that's what I'm going to  talk about today.  And in fact, if you're  interested after I'm done here,  I've got a sample from the cave  I'm working on in Israel that  you can come take a look at.  It's pretty neat up close. 

 So Sorek Cave, this is where  I've done all of my research and  this is a cave that's just out  of Jerusalem, may be  20-kilometers southwest of the  old city.  So we're very close to the  Mediterranean ocean here.  It's an interesting place  because to the west of Jerusalem  you have fairly temperate  climates.  There's a good amount of  rainfall throughout the year.  But if you head just  40-kilometers to the east,  you're standing in the Dead Sea  which is, of course, an  extremely arid climate.  So Sorek Cave is in an area  that's known as a semiarid  climate.  So you get maybe a couple of  feet of rain per year.  But it comes in a very  interesting pattern which we'll  get into here in a minute.  Of course something to keep in  mind, this picture down in the  bottom left is that the key to  building a cave and making a  stalagmite is water.  So you need rain to drip through  the soil and the limestone above  a cave to bring the material to  a stalagmite so that it can  form. 

 And we'll get into some  chemistry of that, just some  basics here, in the next couple  of slides.  So the general chemical equation  for how to make a stalagmite is  there on the top.  We need three ingredients.  Water, carbon dioxide and  calcite, that's what CACO3 is,  it's a mineral.  That's what makes up limestone.  And you can see that in the  cartoon there at the bottom  where we get each of those.  Water obviously is from rain.  CO2 is dissolved into the water  as the rainwater percolates into  the soil.  And then the limestone, the  calcite, is also dissolved into  that rainwater droplet as it  percolates through the soil.  So when you get CO2 and calcite  dissolved in water you end up  with these ions that are shown  the right. 

 So those ions are in solution,  and as the water, the solution,  percolates down through the  ground, you get, all the sudden  to the opening of a cave, and  you because of the difference in  the concentration of CO2 in the  soil and the concentration of  CO2 in the cave atmosphere, the  equilibrium of this reaction  shifts and all of the sudden the  reaction wants go back towards  the left here.  So those ions come out of  solution, and water and CO2 is  released from the drip as it  hangs at the bottom of the  stalactite and limestone then is  precipitated on a stalactite or  on a stalagmite down below where  the drip drops.  So that's how we form a  stalagmite in a cave.  Now the neat thing for this  study is that the oxygen, I just  turned them red there, the  oxygen in the water and the rain  can be related, through  something called oxygen  isotopes, to the oxygen in the  stalagmite that is forming in  the cave.  And so there's obviously some  oxygen in the other components  that make up this reaction.  But by understanding how the  isotopes of oxygen behave, you  can understand something about  past climate.  Now before I lose you, we'll do  a quick review on what an  isotope is, and I've got a  cartoon here on the left.  So isotopes are different  flavors of the same element.  So for instance, on the left  I've got three different  isotopes of hydrogen.  And they can be naturally  occurring and they have varying  abundances. 

 So for instance, hydrogen 1,  which has just a single proton  and no neutrons, is extremely  abundant on earth, whereas the  hydrogen 2, or deuterium, and  hydrogen 3, also known as  tritium, which have increasing  numbers of neutrons in the  nucleus but they all have the  same number of protons, that's  key, they are much less abundant  on earth.  So these varying abundances are  important.  They're different in different  reservoirs.  So similarly to hydrogen, the  element oxygen has three stable  isotopes, which means they're  not radioactive.  And so oxygen 16, 17 and 18 are  the three ones that are common  in nature and so, of course,  oxygen has eight protons in the  nucleus but because it's 16, 17  or 18 it means you can have  eight, nine or ten neutrons in  the nucleus.  So because these different  isotopes are interchangeable in  molecules it means if we can  measure the different abundances  we can use them as a fingerprint  in geology to understand how  these geologic processes and  climate processes are working.  And one last confusing thing  here is how we talk about the  abundance of isotopes in our  samples is using this delta  notation.  And all this is telling us from  this equation here is that we're  comparing the ratio of 18 oxygen  to 16 oxygen in the sample  versus 18 oxygen to 16 oxygen in  some kind of standard.  And we use ocean water for our  standard.  And we multiply that by a  thousand and it's reported in  units per mill. 

 If that doesn't mean anything to  you, that's okay.  The important thing down at the  bottom is that positive values  of delta O-18 is how you say  this term, means you have a  higher ratio of 18 to 16 oxygen  than in your standard.  And negative values of delta  O-18 mean you have a lower ratio  of 18 to 16 isotopes than your  standard.  And throughout the rest of my  talk I'll try and help remind  you there for in stalagmites  higher values of delta O-18  indicate a dryer climate and  lower values indicate a wetter  climate.  So I'll try to put those  indications up so we can keep  that straight.  So quickly here's a brief sort  of overview on work that's  already been done in Sorek Cave  in Israel.  And I've got plotted here the  past 160,000 years worth of  oxygen isotope record taken from  that multiple stalagmites  throughout the cave.  And you can see that there's a  pattern that jumps out and I've  plotted the delta O-18 values  there on the left hand axis.  Again, dry is up and wet is  down.  So you can see that the last ice  age which happened about 20,000  years ago, so two small tick  marks down there, was much dryer  actually in this part of the  world than it is now, it's a  little more moist now. 

 There are, I should mention,  okay we'll go to the other side,  the other axis on the graph here  is on the right side in the  pink.  The pink curve that's plotted  across there is one of those  Antarctic ice cores, and so you  can see halfway around the globe  there are actually some very  interesting patterns that show  up in both records.  And so that's great from a  geologic standpoint because it  means that the climate record  we're recording in Sorek Cave is  somehow related to the record  that's being recorded at the  poles.  So we're seeing some kind of  global influence here.  I've also highlighted there in  red, I'll try and point this  with my mouse, right here you  can just pick it out.  That's the time period of  interest that we're going to  look at the sample that I used  in my masters theses.  And it covers a very short time  period.  Only about a thousand years  starting 2,000 years ago.  So the other important thing is  that this occurs in sort of a  very quiet part of the record.  There's a lot of things going on  in what's controlling the  isotope value of the stalagmite. 

 So we kind of wanted to filter  out some of those other  variables and just focus on a  quiet part of the record.  I should mention that all of  those data points that make up  the blue curve were made with  thousands of little dental drill  holes that were put in  stalagmites just like I showed  you in the previous slide.  So you use a dental drill and  you poke a whole bunch of holes  right next to each other.  They go from the inside, the  inner-most growth rings to the  outer-most growth rings.  And you measure the geochemical,  the isotopes in each of those  samples and then you can build  those records if you know the  age of your sample.  So that's something to keep in  mind is that the conventional  way to analyze these things is  with a dental drill.  And it's got about a half  millimeter drill bit on it.  So the same they use in your  teeth to pick out all these  growth rings.  So kind of where our study is  going is that what about, is  there information that we're to  be gained by analyzing this  stalagmite record at a higher  spatial resolution.  So what if we use a smaller spot  to analyze, instead of a half  millimeter dental drill, can we  find anything else out by using  a smaller analysis size. 

 If so we could ask questions  like do these stalagmites record  seasonal climate variability?  And of course, ideally if we're  going to ask that question we  want to be in an area where  there is a strong seasonal  climate record.  If it was the same all year  long, even if you had seasonal  resolution, you wouldn't be able  to tell because it was all the  same.  It would be constant.  Well it just so turns out that  at Sorek Cave, or in that  semiarid area just outside of  Jerusalem there is a very  distinct climate signal.  So you can see here I've got  plotted in this graph the  average percent of the annual  rainfall for each month that is  plotted there along the horizon  axis.  So you can see that for  November, December, January,  February that's what this area  gets blasted with rain.  And the rest of the year,  essentially, it's bone dry or  almost bone dry.  So you have a very regular  pattern of rainfall in this  area.  I should also mention that this  is data that's been collected in  the area since 1990.  So it's about 20 years worth of  data. 

 And of course, that's another  excellent thing for our study is  that our collaborators in Israel  have spent 20-plus years  studying this cave so not only  did they develop that 160,000  year long record that I showed  in the last slide but they also  collected a bunch of climate  data and data from all over the  cave.  So we can use that to help  constrain the record that we've  developed.  Now I'm going to plot something  on top of this graph now and all  of those blue squares now are  relative to the axis on the  right and that's telling us what  the oxygen isotope composition  is of the rainwater that's  falling above the cave.  And so this gets really neat  because during that period  December, January, February when  the most rain is falling in the  area, you also have a very  distinct oxygen isotope signal  in that rain.  So over the course of the year  these values are averaged but  you can tell, essentially, what  time of the year you're in based  on what the oxygen isotope value  is of the rain that's falling  from the sky.  So there's a distinct pattern  here that we're going to use to  look at a seasonal climate  record in the stalagmite.  So we know we have a pulse of  very low oxygen isotope values  in the rain once a year.  And it turns out that if you  walk into the cave, this signal  that happens once a year is  recorded in the drip water.  So that drip water, the rain  that falls on the ground and  then percolates through the soil  and the limestone and eventually  comes out into the cave, it  preserves that oxygen isotope  signal that we see in the  rainfall.  And so that's great for us  because it means that the  stalagmites might possibly be  reserving that same signal. 

 So we can see that annual pulse.  And here's data from 1991 to  1996.  These are averaged over sort of  three month periods, drip water  that's entering the cave.  You can see there's a regular  pulse there that's showing that  same signal that we saw in the  rainwater.  And so now we know we have some  kind of seasonal signal.  The idea is now from our sample  can we see that signal?  And so in order to do that we  need two things.  First, we need a way to measure  oxygen isotope values with high  precision and high spatial  resolution.  And second, we need a way to  image the annual band so that we  can tell if one annual band we  can see one annual oxygen  isotope signal.  So I'm going to talk briefly  here about the first thing.  The way that we get the high  spatial resolution and the high  precision on those oxygen  isotope values is by using this  ion microprobe and this is a  machine that's about to turn  four years old this weekend. 

 It's a relative, this is sort of  a state of the art instrument.  There are only I think a handful  operational in the world and  we're lucky enough to have the  best team of people in the world  running ours so we get excellent  data here.  And it's very exciting for me as  a graduate student to work in a  lab like this.  There are many different types  of projects that are on here and  we can talk about that  afterwards if you're interested.  So quickly how this machine  works, how we get those very,  very tiny spots.  Here's a schematic of the  instrument.  For those of you that are  interested, it's a double  focusing mass spectrometer  on the second, on the right hand  side, with an ion beam  on the left hand side.  And I'm going to overlay some  pictures here to explain this a  little more clearly.  So the idea is that instead of a  dental drill bit you actually  use a focused beam of ions to  sputter away your sample.  So we can put a little piece of  my stalagmite right down here in  this red box and we focus a  what's called a primary ion beam  which is made up of cesium ions  into a very tight beam. 

 It's only 10 micrometers across  which is about one one-hundredth  of a millimeter.  So we're talking very, very  tight beam.  And that beam is focused then  onto the sample and in this  cartoon in the middle I'm trying  to show you how exactly that  works.  So in come the cesium ions and  they sputter off ions from this  sample surface, and we're  interested in oxygen isotopes  like we've been talking about.  And so those oxygen isotopes  that are sputtered off the  sample are accelerated in what's  called a secondary ion beam into  the mass spectrometer.  And so they're accelerated  around the mass spectrometer  and we can then measure ratios  of oxygen 18 to oxygen 16.  And that gives us those delta  values that we've been talking  about.  Let me go back really quick.  Again, I should mention that the  beam is only in 10 micrometers  in diameter.  It sputters away a little pit  that's only about one micrometer  deep and that's equivalent to  about a nanogram of sample. 

 And typically with those dental  drills they have to measure  powder that's the weight of  which is at least a thousand  times more than this.  So we're measuring samples that  are much, much smaller.  And so that's something that has  never really been done before  with the precision that we're  able to have on this machine.  So quickly, how do we get from a  stalagmite to the machine?  Here is the image that I showed  you before.  I cut a bunch of one centimeter  cubes out of the stalagmite.  And they're all along sort of a  radial traverse there.  So we're taking those steps from  the middle of the tree rings to  the outside of the tree rings or  the growth rings in the  stalagmites' case.  And then I can mount two of  those centimeter cubes into an  inch wide mount epoxy mount.  And that gets polished and put  into the machine.  And I've got one of those up  here also you can check out  after I'm done. 

 So there are the chips.  A, B, C, D, and E.  Those are the those one  centimeters cubes.  Here's an example of how they  are mounted within the mount.  They go in there with some  standard range which we use to  make sure we have a control on  how precise our data is.  And then we can see if there's  any instrument drift or beam  instability we know right away.  So briefly here I'm going to  throw up an image that shows the  first 40 hours of an analysis  session that I did.  Here we go.  So on the left axis here, this  is busy but we're just going to  look at a couple of things here.  The left axis is the raw oxygen  isotope values measured on the  machine. 

 All those green dots on the top  are the sample, so the  stalagmite that we measured.  And the red and blue dots down  at the bottom are the standard.  And so those are important for  constraining, again, the  precision of the data we've got.  The few things that I wanted to  mention here before I move on  because we're going to compare  it to the data that I  collected, are one, the  variation in those green dots at  the top.  You can see there is about 3 per  mill.  It goes from 20 to about 23 on  that scale.  So remember that.  There are 427 analyses all  across the sample that we did in  40 hours.  So this machine you can really  sit there and crank out the  data.  You've got about four minutes to  go and read a sentence or run to  the bathroom but you've got to  be back on that machine as soon  as it's done to go to your next  spot. 

 So it's an exciting time.  And yes, those are continuous so  overnight and through the day.  And the last thing that I want  to show here is that the  precision that we obtain using  our standards is the standard  deviation is .17 per mill.  And if you compare that to other  labs that have done this on  similar types of samples, the  one standard deviation that they  get is three, or more sometimes,  times higher than us.  So we have very precise data for  this type of study.  Okay, so now this is why I  wanted you to remember those  things.  Here is the conventional drill  data across those same five  one-centimeter plugs.  And you can see the most that  they could fit in there was 65  analyses and we did 427.  So we've got a lot more data to  work with.  And if you notice the  conventional drill data there  only has about one unit of  variation on the per mill axis  there where as you remember the  green arrows there are showing  the three per mill that we saw  on the ion probe. 

 So immediately it's obvious that  we must be collecting more  information here which seems to  make sense since we're at a  higher resolution.  And just a note quickly on what  sort of time resolutions we're  talking about, the outer-most  portion of this sample you get  50 or 60 years for each one of  those drill spots whereas the  inner-most portion of the sample  you're looking at eight or nine  years that's being integrated  within each single drill spot.  And I'm going to show you in a  minute that we're actually  getting sub-annual resolution  which is very exciting.  So quickly the second thing we  need for this study is it is a  way to image these annual bands.  And the way we've done that is  with a something called a  confocal laser fluorescent  microscope.  And this gives us these  brilliant green images, and  we've taken this across the  whole traverse that we did our  isotope analyses and you can see  growth bands here and we've done  this, I'll explain a little bit  what they mean, we've done this  at the Keck lab here on campus  in the Medical Sciences Center.  And so here's sort of a step  back, that little red box over  there shows the last image I  just showed you.  You can see there's kind of a  regular pattern that sticks out  here as we go from older to  younger, right to left.  It seems that there is a sharp  boundary where you get a bright  green fluorescent band and then  it grades to darker and darker.  And then you get another sharp  bright green boundary and then  is it grades to darker and  darker. 

 And the way that microscope  works is you have a focused  laser that will make organic  molecules vibrate and this wave  length of laser that's coming  into the organic molecules and  vibrating them around will be  reemitted at a characteristic  wave length depending on what  the organic molecule is.  And so it turns out this green  light is produced by what we  think are humic and folic acids  which are those acids that occur  in the soil column when plant  matter decays.  So we think that this regular  pattern going from bright  fluorescents to dark  fluorescents in a single band is  showing that pulse that we  talked about in the rainfall.  So you get heavy rains is going  to push all these organic acids  from decaying material in the  soil column into the cave and  that's going to get trapped in  the stalagmite as it grows, and  then later in the year when  there's not as much of this  humic acid left in the soil, you  don't get as much organic acids  and so you don't get the  fluorescents.  So we think those are the annual  bands, that regular pattern of  light to dark fluorescents.  So here again is the blow-up of  that pattern.  Just quickly I've shown the  yellow circle there is showing  what that dental drill analysis  is integrating.  So you can see there's a lot of  bands that are collected all in  one analysis.  So there's a lot of information  potentially being lost.  The gray box there is showing  the outline of the next image  I'm going to show you here. 

 So this is where I've done the  isotope analysis on the ion  probe.  So there's that same section.  And now each of those tiny  little white spots there that  are outlined is an ion  microprobe pit.  So those are those 10 micrometer  pits.  And, plotted both above and  below versus the vertical axis,  are the oxygen isotope values of  each one of those pits.  And so you can see that it was  exciting to discover that the  oxygen isotope values correlate  quite nicely with the  fluorescents of the band.  And so you can see at the top  here as you go from a  fluorescent band, you have the  lowest oxygen isotope values  which are wet, again, and then  as you go towards darker and  darker fluorescents you get  higher and higher oxygen isotope  values.  And this pattern repeats itself  again and again across all these  bands.  And again remembering that  pattern, we think back to the  drip water.  So this looks like we possibly  are recording this annual cycle. 

 So what does this mean?  Here's a quick cartoon of the  data interpretation as we see  it.  So the top shows that traverse I  just showed you with the oxygen  isotope values.  And I've got the fluorescents  there indicated at the top.  And down at the bottom we've  just got the explanation.  So the light zone in each band  where we have the lowest oxygen  isotope values, so for instance  here and here, that's where the  organics, those humic acids are  collecting.  And that represents the wet  season.  So that pulse of rain every  year.  And then as you go on through  the band you get to the dark  zone and that's represented by  the high delta O-18, the high  oxygen values, where there is  fewer organics and that's  representative of the dry part  of the year when there's almost  no rain.  Now there's some interesting  things that we've pulled out of  this, in that for each band that  we could identify across the  sample, we measured the highest  and lowest oxygen isotope  values, so right at the edge of  each band and we took the  difference between those values  and we plotted them up for each  band that we could across the  whole sample and what I've got  then in the graph at the bottom  is showing how that sort of the  gradient across the single band  changes through time and again  we're going from 2,000 years ago  to only about 1,000 years ago.  That's when the stalagmite grew. 

 And so we think that the, when  you have a big difference  between the beginning and end of  a annual band in oxygen isotopes  that means you've got a very wet  year so there's a very powerful  signal that was transmitted into  the cave.  And during the dry years, the  difference is very small.  So this gives us the ability on  a year to year basis to tell a  wet year from a dry year.  Also, an independent measure we  made was using the modern  observation that annual rainfall  amount in the region can  correlate actually with the  annual average isotope value in  the rain.  So this slope that I've got  plotted there at the top shows  the modern observations in  rainfall.  And you can see again that very  high isotope values represent  very dry periods.  So there's almost no rainfall in  this particular year.  But in a very wet year, down  here is almost a meter of rain  or a little more, the annual  isotope value for a year's worth  of rain is much lower.  So using that correlation we've  estimated the rainfall for each  one of these bands through time.  So now we have a way to, a rain  gauge essentially from 2,000  years ago to 1,000 years ago in  this cave just outside of  Jerusalem. 

 So you can see that through time  not only in the last plot but in  this plot, and I'm going to  stack them here in a minute, it  appears that we go from sort of  relatively wet conditions to  much dryer conditions.  Panel B, the second one there,  again that's the gradient that  we measure decreases greatly  indicating possibly a much dryer  climate.  Our precipitation estimates also  decrease greatly from just over  a meter of rain per year to as  low as half a meter of rain per  year.  And the top are the raw data and  again if you remember that  general relationship between wet  and dry, we go from much lower  values to higher values.  So it appears that during this  time period things went from  being fairly wet to being much  dryer.  And the cool thing is down here  at the bottom this is  an independent proxy  of paleo rainfall.  And if you imagine the Dead Sea,  which is only 50-kilometers or  so away, as a regional rain  gauge, it's collecting all the  rainfall from the surrounding  area.  And through time you can imagine  if you had a lot of rainfall the  Dead Sea would fill up and if it  got dryer the Dead Sea would go  down again.  And this is data that has been  collected by other scientists in  Israel.  And you can see that down here  where we think it was the  wettest, the lake levels were  the highest. 

 And at these periods where we  see some large drops, they  correspond to the drops in the  Dead Sea level that have been  observed.  So the fun thing about this  study has been that this is an  extremely interesting area sort  of in terms of, well culturally  as well.  And so across the time period  that we looked at, 2,000 years  ago to 1,000 years ago, I've  just got some very general sort  of events through time here.  Of course, this is zero and  we're increasing in time to the  left to about 1100 AD when the  first crusade happened.  And the neat thing is that the  Byzantine Empire in this region  was finally flushed out of the  sort of area surrounding  Jerusalem at about 636 at this  battle called the Battle of  Yarmuk.  And whether or not there is a  direct tie between climate and  the down fall of the empire in  this particular region, we're  not sort of ready to say yet.  But the correlation is  nonetheless interesting.  You can imagine that here I've  got our rainfall estimates  plotted.  It's a little bit stretched and  squished there, but you can see  that as it dries out we go from,  possibly this has some lasting  implications as far as  agricultural and trade go in the  region.  So that might be one reason  amongst many that the empire has  been, the Byzantine Empire has  moved out of this area. 

 So quickly some conclusions.  We've come up with that  stalagmites are definitely a  valuable climate proxy.  The ion microprobe analysis, in  particular, achieves very high  temporal resolution, much higher  than the drilling we've seen.  And with that, we observe some  isotope variations across a  single annual bands, and so  where we go with this in the  future we hope to apply this to  much older records or records  from different parts of the  world where these seasonal  changes are very interesting and  could be applied to these  climate models.  Again, the capital delta O-18 or  the gradient we observe there,  that records trends in  seasonality through time  of these wet and dry years.  And finally the delta O-18 or  the isotope value of those  fluorescent bright bands that  are representative of the wet  season can be used as records of  annual paleo rainfall amount.  And so lastly I'd just like to  acknowledge all the people that  have helped me with this study,  and hopefully you've learned  something, and I'd be happy to  take your questions.  [APPLAUSE]