Climate Monday: NASA Animations of Ice Sheet Loss

February 19th, 2018

Two weeks ago on Climate Monday, I highlighted some different visualizations of sea ice loss in the Arctic. Monitoring the sea ice regime is important for knowing the limits of human navigation, resource extraction, and other activities in the Arctic, but the subsequent decline in land ice has a much broader impact on humans because melting land ice leads to sea level rise. You may have seen time lapses of retreating glaciers before, like this time lapse of Columbia Glacier in Alaska. That is dramatic and provocative, but in the long term, the two most important sources of ice melt are Greenland and Antarctica.

Artistic depiction of the GRACE satellites from the NASA Earth Observatory.

One of the main ways we monitor the loss of mass from these ice sheets is the GRACE satellites. GRACE (Gravity Recovery and Climate Experiment) is a pair of satellites launched in 2002 that follow each other around the world about 120 km (90 miles) apart. What they actually measure are very slight variations in that distance between them, and this is indirectly but accurately measures the regional gravitational pull of the Earth.  The stronger Earth’s gravitational pull, the faster the satellites will orbit.  Since they’re 90 miles apart, when the first satellite passes over an area with greater mass (and therefore a stronger gravitational pull), it goes a little faster and the distance between the two satellites expands.  Then, when the second one passes over the same spot, it catches back up and shrinks the distance. That variation in distance tells NASA scientists how much mass comprises various regions of the Earth.  It can’t detect small changes like constructing a new building or cutting down a stand of trees.  But it can detect large changes like long-term groundwater withdrawal or melting ice sheets.

NASA has put together two animations that show this system at work in Greenland and Antarctica. The beauty of these animations is that they pair a time series of mass loss with a map of the decline in the height of the ice sheet. (Be careful; the change in “height” of the ice sheet is measure in “water equivalent”, which means they’re reporting the loss as liquid water, not ice.  This is done because the density of water is less variable than the density of ice.  Using water makes it easier to compare different areas.) In Greenland, you can see the seasonal cycle of accumulation in winter and melt in summer, but the overall decline is also obvious.  Most of the ice sheet has lost mass, but the greatest loss has been at a few really large glacial outlets. Overall, there’s about 0.8 mm (0.03 inches) per year of sea level rise coming from Greenland right now. That’s not huge, but combined with mountain glaciers, Antarctica, and thermal expansion, it’s been around 3 mm (0.12 inches) each year overall since GRACE was launched.

Although not very important right now, Antarctica is the most important mass of ice for the long haul. If the entire Antarctic ice sheet melted, it would add roughly 9 times as much water to the oceans as Greenland would (roughly 60 m versus 7 m, respectively). That isn’t going to happen under current projections — but by 2100 we could very well see a meter. The animation starts in 2002 and shows how much mass loss occurred through 2016. The average loss is 125 gigatons per year, which sounds like a lot.  It is, to be sure, but it’s only a small amount of sea level rise — about 0.35 mm (0.014 inches) per year.  So right now, Greenland is still the bigger contributor. The really cool thing about the animation is that you can see that current mass loss from Antarctica is restricted to just a few places.  The Antarctica Peninsula is one place, which makes sense; it’s the farthest north and warmest area of Antarctica. But another is in “West Antarctica” (on the left of the map). This area is losing mass fast, especially Thwaites Glacier and Pine Island Glacier. But overall, Antarctica is contributing only very a small about of melt to the oceans compared to its potential.

Climate Monday: NERSC Surface Pressure Observations

February 12th, 2018

Although we often care more about the temperature and precipitation when we talk about weather, the most basic weather observation we can make is atmospheric pressure. Atmospheric pressure is really a measure of how much air is above you. That might not seem like a big deal, but clear skies are characterized by high pressure (e.g., 1020 hectopascals, or hPa) whereas storms are characterized by low pressure (e.g., 980 hPa). So air pressure was an early method of short-term weather prediction. If the pressure is dropping, a storm will likely follow. And once the pressure starts rising again, the worst is likely over. That’s useful. What’s also useful is that air pressure is easy to measure. Evangelista Torricelli made a functional mercury barometer back in the 1600s.  Today, air pressure is still one of the basic variables used to characterize weather and make forecasts.

The surface pressure network as of January 1851 (beginning of the animation).

Today’s climate visualization is 160 years of weather observations by Philip Brohan.  It’s a gargantuan 13-minute animation of all surface pressure observations dating back to 1851 that are currently freely available to the scientific community. Every frame shows all measurements for a 3-day period. That is precise! And some of the patterns are fascinating. At the beginning of the record, most of the data are from ship observations. The only land stations are in North America and Europe, and even those are limited.  Throughout the late 1800s, the USA, Europe, Russia, and Australia all see increasing coverage. At sea, changes in ship technology is apparent, as individual ships make a greater range of observations as time progresses.  The opening of the Suez and Panama Canals is also obvious. Several countries show abrupt increases in the density of their pressure networks. Japan suddenly has ample coverage in 1901; Germany increases density in the 1930s that far exceeds France. During WWII, India suddenly has a broad network, and Germany’s network reaches a peak in coverage that suddenly drops after the war. eastern China’s network becomes large in the 1950s, falls back in the 1960s, and then stays dense for good in the 1970s. Finally, the breakup of the USSR in 1991 was accompanied by a major decrease in surface pressure observations.

I have not dug too deep into the history of these observations, but this animation is a good window into how human technology and society can impact the availability of scientific data.  We are still reliant on shipping lanes to this day for pressure observations, and we know more about the North Atlantic than the South Pacific.  For more information about the data source, check out Internatonal Surface Pressure Databank.

The surface pressure network as of March 1970 (9:45 in the animation).



Climate Monday: Four Ways to Visualize Arctic Sea Ice Decline

February 5th, 2018

During the Spring 2018 semester, Monday is Climate Day.  To make it even more thematic, I’m focusing on various ways of visualizing climate and weather data.  Today’s topic: the long-term decline of Arctic sea ice since 1979.

Scientists have long known that global warming would cascade throughout the Earth’s climate system and lead to many indirect effects of carbon dioxide accumulation in the atmosphere. However, the rapid decline in the Arctic’s sea ice cover was one of the earlier indications that climate change was not just in our future, but also our present. The classic way to present this decline is with two figures: a map and a graph (Figure 1).

Figure 1. (top) Map of average September Arctic sea ice extent for 2017 (compared to median extent for 1981-2010) and (bottom) time series (with linear trend) of September Arctic sea ice extent for 1979 to 2017. (National Snow and Ice Data Center)

Why September?  September is the month that Arctic sea ice reaches its minimum extent. Each winter, sea ice expands out of the Arctic Ocean into lower latitudes like Hudson Bay and the Bering Sea.  Each summer, it retreats back to the central Arctic Ocean. September is the end of summer, so any sea ice leftover at that minimum is part of the “perennial” or “permanent” sea ice cover. The rest is just temporary.

These two plots are helpful scientific tools.  For instance, you can see in the map that on average from 1981-2010, there was no open water passage through the Arctic.  In 2017 it was possible to send any sea-worthy vessel through. On the graph, you can see how in the year 1996, there still was no clear climate change signal.  But 20 years of decline later, the trend is obvious.

However, this version of showing sea ice can be hard to wrap your head around in terms of scale.  How big is 8 million square kilometers anyway? This is where Option #2 comes in.

Figure 2. Arctic sea ice loss from 1980 to 2012 compared to the size of the United States. (Courtesy of Walt Meier)

In the Figure 2 on the left, white states are equal to the area of sea ice that existed in both 1980 and 2012. Blue states are equal to the area that had sea ice in 1980 but not in 2012. In other words, blue states are equal in area to the sea ice loss between 1980 and 2012.  This figure, by Dr. Walt Meier, helps put sea ice loss into perspective, because that’s not just an analogy; those areas of the states are equivalent to the areas of summer sea ice. So it’s not only that there’s been more than a 50% reduction; a vast area of ocean half the size of the lower 48 used to be covered with ice year-round, but now is seasonally open.

But this still isn’t very flashy, so some people have gone the route of animation. Option #3 is animating the maps of Arctic sea ice extent that come from the National Snow and Ice Data Center (Figure 1). This maintains the basic science data approach of Option #1 but adds the animated aspect to help your eyes compare the shape of sea ice extent, not just a dot on a graph.  Of course, it can be hard to tell precisely how much sea ice there is in a given year, so this is solely a communication tool, not a research tool.

A more recent type of animation that has become especially popular on Twitter is the “death spiral”.  Now we are fully in the “communication” realm because the title assigned to this flavor of animation is using charged language.  I personally find the term “death” here excessive.  However, putting the alarmism aside, the animation can be informative.  Around the edge is every month of the year.  The sea ice volume (from the Pan-Arctic Ice Ocean Modeling and Assimilation System, or PIOMAS) is 0 cubic kilometers at the center and 35 million cubic kilometers at the edge. Having the Arctic map in the background is superfluous and possibly distracting, but this is the most recent version of the style I could find.

This animation does a decent job of showing both a) the seasonal cycle of sea ice growth in winter and melt in summer and b) the long-term trend of declining sea ice volume. Note, though, that this is a bit different from measuring sea ice extent.  Sea ice extent is a 2-D measure of the surface area of sea ice in the Arctic. Sea ice volume is 3-D; it’s the area times the thickness of sea ice.  Thickness is harder to measure than extent, and PIOMAS assimilates model output with a combination of observations from aerial and satellite remote sensing instruments. Although less confidence can be placed in the precision of the numbers, this metric tells the same story as sea ice extent.

I’d love to hear opinions about which type of presentation you like the best!

Climate Monday: Keeling Curve Animation from NOAA

January 29th, 2018

While Dr. Wilson is away on leave this semester, I am going through 15 weeks of “Climate Monday”, in which every week I get the opportunity to highlight one graphic or animation or data tool that shows something interesting about climate (and weather). I’m also using these tools to share a little climate science. Last week I highlighted a weather animation tool, so this week is fully in the realm of climate with NOAA’s animated Keeling Curve (also on youtube).

map of mauna loa observatory

The Scripps carbon dioxide program, including the Mauna Loa Observatory. (Image Credit: Scripps Institution of Oceanography)

Humans have decades of direct observations of carbon dioxide concentration in the atmosphere. The longest continuous record dates back to March 1958, when C. David Keeling started analyzing air at the Mauna Loa observatory in Hawai’i. Mauna Loa is a good place to make such measurements because Hawai’i is isolated from major industrial regions like the Midwest of the USA, the Ruhr Valley in Germany, and the Pearl River Delta in China. There is relatively little regional pollution (although there is some from cities like Hilo and Kona, and from nearby islands like Oahu and Mau’i). The composition of the air in Hawai’i is a better reflection of the Earth’s average atmosphere than measuring, say, at LAX or O’Hare.  Atmospheric measurements have been made up on Mauna Loa ever since.

The Mauna Loa Observatory (Image Credit: Theo Stein, NOAA)

The resulting data is the Keeling Curve, which is plotted below. The “sawtooth” pattern of the red line is the seasonal cycle of winter and summer in the Northern Hemisphere.  In summer, plants take up carbon dioxide during photosynthesis, reducing carbon dioxide concentration. In winter, photosynthesis slows or stops throughout much of the Northern Hemisphere, and carbon dioxide can accumulate in the atmosphere. So carbon dioxide is always a bit higher in winter than it is the following summer. The black line has the seasonal cycle removed, so it shows the year-to-year changes in carbon dioxide. It also shows the increase from under 320 ppm in the 1950s to over 400 ppm today.

This is all really cool to seem but there is much more to our record of carbon dioxide than just Mauna Loa.  NOAA has put together an animation that shows all of the dozens of other sites around the global that record carbon dioxide concentration and how that record has changed through time. It also puts that record in the context of paleoclimate. Seeing the whole animation, you can detect all of the nuance in the global carbon dioxide record.  For instance, the Northern Hemisphere has a much stronger seasonal cycle than the Southern Hemisphere since it has substantially more land plants at mid and high latitudes.  Other locales are even more variable, like many in the continental USA closer to major industrial centers. The South Pole generally lags a little behind the Northern Hemisphere, in part because it takes awhile for carbon dioxide emissions to mix throughout the whole atmosphere.


Climate Monday: Weather Animations by Cameron Beccario

January 22nd, 2018

While Dr. Wilson is on leave and taking a hiatus from his acclaimed “Fossil of the Week” series, the Department of Geology decided to fill the void with something completely different: Climate Monday. For 15 weeks in the Spring 2018 semester, I am going to highlight one animation, graphic, or online tool that helps visualize some aspect of the climate system. Some are about weather, some about climate. Most are about the atmosphere, but the ocean comes into play as well.

I want to start with a bang, so first up is my favorite weather animation: Cameron Beccario’s “Earth”. A screenshot below is from just after  New Years’, when a nor’easter was blasting the northeast USA and cold Arctic air was surging southward over the Midwest.  (Wooster, OH is in the middle of the little green circle.) This is a beautiful image on its own. The swirling convergence of wind around the nor’easter turns red to indicate the high wind speeds. The easterly Trade Winds blowing off Africa are clearly defined. Two additional winter storms can be seen by the clustered wind streamers and red coloring in the North Atlantic and North Pacific Oceans, although neither is as tight and powerful as the East Coast blizzard.

Screenshot of wind animation for 5 January 2018, from Cameron Beccario’s weather animation tool. Redder colors indicate stronger wind and the streamers indicate wind direction.

But that’s just a glimpse at what this tool can do.  Besides staring at colorful wind patterns and watching cyclones churn, users can pan around the entire Earth, zoom in and out, change the color variable to temperature, humidity, or cloud density, even aerosols or ocean currents.  You can toy around with different projections, examine different levels of the atmosphere, and even go back in time.

The data behind these animations are from a variety of sources.  Cameron Beccario has integrated the National Oceanic and Atmospheric Administration’s (NOAA) Global Forecasting System (GFS), version 5 of NASA’s Goddard Earth Observing System (GEOS-5), various other datasets from the US and EU agencies, as well as a few non-profits. Underlying most of these monitoring systems are a combination satellites, surface observations, and atmospheric models. These are the same tools used for weather prediction and analysis, so although it’s not a research tool, Beccario’s animations have high-qaulity data behind them, and they’re the best animations of atmospheric and oceanic data I’ve seen.

For a little more fun, here’s a glimpse at the aerosols.  More specifically, this is the dust concentration from the same day: 5 January 2018.  I focused this on the widespread dust coming off the Sahara Desert. Some of those dust particles can end up as far away as Florida and Texas.

Screenshot of dust concentration on 5 January 2018 from Cameron Beccario’s weather animation tool. The tanner the color, the more dust.

Sometimes zooming in on a feature can be fun.  Here’s an example of the Gulf Stream, a warm water current along the western boundary of the North Atlantic Ocean that hugs the east coast of the USA from Florida to Cape Hatteras.  It’s because of this current that the Atlantic Coast of southern Florida often have warmer water than the Gulf Coast in winter. Beach-goers be aware!

Sea surface temperatures and ocean currents on 5 Jan 2018 from Cameron Beccario’s weather animation tool. Red is hot; blue is near freezing.

Weather Sensationalism: Boston is colder than Mars

January 4th, 2018

Today, CNN and several other news outlets are reporting that “Boston and part of New Hampshire will be colder than Mars” this weekend. At first glance, this sounds incredible.  It’s going to be really cold this weekend! Indeed, on Saturday, the coldest day forecasted, Boston is expected to see a low of -7°F (The Weather Channel), -4°F (AccuWeather), or -2°F (Weather Underground)… so yes, this is cold.

CNN headline from January 4, 2018 declaring that “Parts of the East Coast will be colder than Mars”.

But there are two things misleading with the statement “Boston will be colder than Mars”. First, the statement makes you think about this cold snap is a big extreme. The thing is, Boston can get colder. Last year on February 14, the low was -9°F, and on February 9, 1934, Boston had its record low of -18°F (NOAA).  Normally, the coldest temperature of the year in Boston is about 2°F (ibid.). So this isn’t unprecedented, even though it’s rare.  It’s an extreme, but nothing to put down in the history books.

The second misleading part is the comparison to Mars.  Yes, Mars is roughly 1.5 times farther away from the Sun than we are, and it has almost no atmosphere, so it on average much colder than Earth. In fact, the average temperature on Mars is about -81°F, whereas Earth is about 57°F (NASA Mars Facts). But wait! -81°F is much colder than Boston has ever been.  So what gives?  The numbers CNN are using come from the Rover Environment Monitoring Station (REMS), which was deployed in Gale Crater along with the Curiosity Rover. If you go to the REMS page and use the arrows on the big weather widget to go back to December 31 (Earth time), you’ll find a temperature of -19°C, or -2°F, as the maximum at Gale Crater. That’s warmer than (or as warm as) Boston is expected to be this weekend.

But this is a bad comparison because they compared the low temperature in Boston to the high temperature on Mars. Compare to the low temperature in the Gale Crater instead, and you have -79°C to contend with, or -110°F. So based on the lows, Mars is still colder than Boston.

Air temperature reported by the REMS instruments aboard the Curiosity Rover in Gale Crater, Mars on December 31, 2017 (Sol 1921).

However, there are two other things that make this comparison misleading. First, they are comparing Boston, at 42°N on Earth to the Gale Crater on Mars, at 5.4°S (REMS).  They are comparing a mid-latitude location in winter on Earth to a location near the Equator of Mars. The Equator of Mars is relatively warmer than the mid-latitudes of its winter hemisphere.

Second, Boston in winter is often colder than Gale Crater. Mars has very little atmosphere and no ocean, so daily and seasonal temperature swings at the surface are much greater than on Earth.  In summer, Gale Crater can exceed 32°F. In fact, if you look back to when Curiosity first landed on Mars, it recorded a high temperature of 37°F on Sol 10. (See that lower graph on the REMS page.) The average high temperature in Boston in January is only 36°F (NOAA).  So being “colder than Mars”, at least based on CNN’s loose phrasing, is not particularly strange.

With all that said, it will be cold in Boston this weekend after the blizzard, so bundle up, New Englanders!

Wooster Geology at AGU 2017

December 18th, 2017

The Mississippi River in New Orleans, Louisiana. Photo: Dr. Karen Alley

Three Wooster Geologists (Dr. Karen Alley, Dr. Alex Crawford, and senior Geology major Cole Jimerson) descended on New Orleans last week to attend the Fall Meeting of the American Geophysical Union. With 20 to 25 thousand attendees each year, this is the largest Earth and space science meeting in the world.

On Wednesday, Dr. Crawford gave a talk about his research in seasonal sea ice prediction. As the Arctic continues to warm, seasonal sea ice melt is occurring progressively earlier each year. Although almost unheard of 20 years ago, commercial shipping along the Russian coastline (the “Northern Sea Route”) is now a routine summer operation. However, the seasonal timing of when the sea ice melts enough for normal shipping is highly variable from year to year. Dr. Crawford and his collaborators are investigating various ways of improving our ability to predict that variability. Better predictions can aid shipping companies in planning their summer routes.

The Northern Sea Route through the Arctic Ocean and the “last retreat day” (LRD), which means the last day of the year on which sea ice concentration is above 50% (left) or 15% (right). Adapted from Stroeve, Crawford, & Stammerjohn (2016); 10.1002/(ISSN)1944-8007.

On Thursday, Dr. Alley gave an invited talk about a new data product she and her collaborators have developed for researchers studying the Antarctic ice sheet. Using ice velocity derived from satellites and sophisticated mathematics and computer coding, they calculated strain rates for Antarctica’s ice sheet and ice shelves. These strain rates are a measure of how fast the ice deforms by stretching and compressing as it moves. They are a fundamental parameter to know for anybody trying to understand how Antarctica’s ice is responding to climate change.

Strain rates on the Filchner Ice Shelf, Antarctica. From Dr. Karen Alley.

Finally, Cole Jimerson presented a poster on Friday overviewing some of the research he and other students performed through a Keck Geology project concerning erosion rates on the Caribbean Island of Dominica. Dominica is a volcanic island prone to explosive ash eruptions. Many of the rocks and sediments on the island are quickly eroded by rivers and chemical weathering in the hot, wet tropical climate. These and other factors lead to landslide risks, and better understanding erosion rates can improve hazard mitigation strategies.

Cole Jimerson presents his poster at the Fall Meeting of the American Geophysical Union.

Wooster’s Fossil of the Week: Echinoid bite marks from the Upper Cretaceous of southwestern France

November 30th, 2017

Above is another beautiful image from Paul Taylor’s paleontological lab at the Natural History Museum, London. It is one of our fossil oysters (Pycnodonte vesicularis) from the French Type Campanian collected in the town of Archiac in southwestern France on our most enjoyable expedition this past summer. The fine crossing short grooves are bite marks produced by grazing regular echinoids (sea urchins). They form the trace fossil Gnathichnus pentax Bromley, 1975. You can learn more about this type of fossil in a previous blog entry describing Cretaceous Gnathichnus from southern Israel.

This is a good time to update our readers on the French Campanian sclerobiont project. Macy Conrad (’17) has done extraordinary work identifying the hundreds of encrusting bryozoans on our oysters. She is using a series of mugshots of Campanian bryozoans produced by our colleague Paul Taylor to name our specimens as accurately as possible. All the pink you see in these trays represents bryozoans that have been identified.

Here is a closer view. Very distinct patterns of diversification of bryozoans and trace fossils upward through the stratigraphic column are emerging. Macy will continue this work next semester as she finishes her Independent Study thesis. I will be doing my parts as well, but from a bit of a distance: I’ll be on a research leave next semester.

Which leads me to this announcement: Wooster’s Fossil of the Week will no longer be weekly. Since I’ll have other writing goals and travel plans over the next several months during my leave, I will contribute blog entries less frequently. The name “Fossil of the Week” has become a bit of a brand, so I’ll keep it, just no longer post every week (which I’ve been doing since January 2, 2011).



Wooster’s Fossils of the Week: Barnacle borings from the Cretaceous of southwestern France

November 24th, 2017

Small comma-shaped trace fossils this week in a Cretaceous (Upper Campanian) oyster (Pycnodonte vesicularis) from the Aubeterre Formation of southwestern France. (Locality C/W-747, Plage des Nonnes, to be exact.) These are borings produced by barnacles, which are sedentary crustaceans more typically found in multi-plated shells of their own making. We’ve seen this fine type of boring before in this blog, so some of this information is repeated.

These boring barnacles (yes, I know the joke) are still around today, so we know quite a bit about their biology. (More on how in a minute.) These acrothoracican barnacles drill into shells head-down and then kick their legs up through the opening to filter seawater for food. They’ve been doing it since the Devonian (Seilacher, 1969; Lambers and Boekschoten, 1986).

This particular trace fossil is Rogerella elliptica Codez & Saint-Seine, 1958. It is part of a diverse set of borings collected on our wonderful field trip this past summer to the Bordeaux region with Paul Taylor.

We know so much about boring barnacles because Charles Darwin himself took an almost obsessive interest in them early in his scientific career. While on his famous voyage on the HMS Beagle, Darwin noticed small holes in a conch shell, and he dug out from one of them a curious little animal shown in the diagram below.

Cryptophialus Darwin, 1854

He called it “Mr. Arthrobalanus” in his zoological notes. He figured out early that it was a barnacle, but he was astonished at how different it was from others of its kind. He later gave it a scientific name (Cryptophialus Darwin, 1854) and took on the problem of barnacle systematics and ecology. Eight years and four volumes later his young son would ask one of his friends, “Where does your father do his barnacles?” The diversity of barnacles played a large role in Darwin’s intellectual development and, consequently, his revolutionary ideas about evolution (Deutsch, 2009).

Burrowing barnacle diagram from an 1876 issue of Popular Science Monthly.


Codez, J. and Saint-Seine, R. de. 1958. Révision des cirripedes acrothoracique fossiles. Bull. Soc. géol. France 7: 699-719.

Darwin, C.R. 1854. Living Cirripedia, The Balanidae, (or sessile cirripedes); the Verrucidae. Vol. 2. London: The Ray Society.

Deutsch, J.S. 2009. Darwin and the cirripedes: Insights and dreadful blunders. Integrative Zoology 4: 316–322.

Lambers, P. and Boekschoten, G.J. 1986. On fossil and recent borings produced by acrothoracic cirripeds. Geologie en Mijnbouw 65: 257–268.

Seilacher, A. 1969. Paleoecology of boring barnacles. American Zoologist 9: 705–719


Wooster’s Fossils of the Week: Encrusting cyanobacteria from the Upper Ordovician of the Cincinnati region — now published

November 17th, 2017

1 pdt19598 D1253[This week’s post is a repeat from last year, with some modifications. The paper Paul Taylor and I wrote on these microbial beauties has just appeared this week in the latest issue of the journal Palaios. A pdf is yours if you send me an email message.] Update: The paper is now a cover story.

Deep in the basement of the Natural History Museum in London, Paul Taylor and I were examining cyclostome bryozoans encrusting an Upper Ordovician brachiopod with a Scanning Electron Microscope (SEM). This is one of our favorite activities, as the SEM always reveals tiny surprises about our specimens. That day the surprises were the smallest yet – fossils we had never seen before.

2 Infected brachWe were studying the dorsal exterior surface of this beat-up brachiopod from a 19th Century collection labelled “Cincinnati Group”. (Image by Harry Taylor.) We knew it was the strophomenid Rafinesquina ponderosa, and that the tiny chains of bryozoans encrusting it were of the species Corynotrypa inflata. We’ve seen this scene a thousand times. But when we positioned the SEM beam near the center of the shell where there was a brown film …

3 pdt16920 D1253… we saw that the bryozoans were themselves encrusted with little pyritic squiggles. These were new to us.

4 pdt19580 D7139In some places there were thick, intertwining mats of these squiggles. We later found these fossils on two other brachiopod specimens, both also Rafinesquina ponderosa and from 19th Century collections with no further locality or stratigraphic information.

5 pdt19578 D7139Paul and I scanned these specimens again and began to put together an analysis. We believe these are fossil cyanobacteria. They are uniserial, unbranching strands of cells that range from 5 to 9 microns in length and width. Some of individual strands are up to 700 microns long and many are sinuous. The cells are uniform in size and shape along the strands; there are no apparent heterocysts. They appear very similar in form to members of the Order Oscillatoriales.

6 CyanobacteriaCyanobacteria are among the oldest forms of life, dating back at least 2.1 billion years, and they are still abundant today. The fossils are nearly identical to extant forms, as seen above (image from:

7 pdt19599 D1253Paul made this remarkable image, at 9000x his personal record for high magnification, showing the reticulate structure preserved on some of the fossil surfaces. Note that the scale bar is just 2 microns long. These are beautiful fossils in their tiny, tiny ways.

We have not seen these cyanobacteria fossils before on shell surfaces, so we submitted an abstract describing them for the Geological Society of America annual meeting in Denver this September. We are, of course, not experts on bacteria, so we are offering our observations to the scientific community for further discussion. Here is the conclusion of our abstract —

“We suggest the cyanobacterial mats developed shortly before final burial of the brachiopod shells. Since the cyanobacteria were photosynthetic, the shells are inferred to have rested with their dorsal valve exteriors upwards in the photic zone. That Cincinnatian brachiopod shells were occupied by cyanobacteria has been previously well demonstrated by their microborings but this is the first direct evidence of surface microbial mats on the shells. The mats no doubt played a role in the paleoecology of the sclerobiont communities on the brachiopods, and they may have influenced preservation of the shell surfaces by the “death mask” effect. The pyritized cyanobacteria can be detected with a handlens by dark squiggles on the brachiopod shells, but must be confirmed with SEM. We encourage researchers to examine the surfaces of shells from the Cincinnatian and elsewhere to find additional evidence of fossilized bacterial mats.”


Noffke, N., Decho, A.W. and Stoodle, P. 2013. Slime through time: the fossil record of prokaryote evolution. Palaios 28: 1-5.

Tomescu, A. M., Klymiuk, A.A., Matsunaga, K.K., Bippus, A.C. and Shelton, G.W. 2016. Microbes and the Fossil Record: Selected Topics in Paleomicrobiology. In: Their World: A Diversity of Microbial Environments (pp. 69-169). Springer International Publishing.

Vogel, K. and Brett, C.E. 2009. Record of microendoliths in different facies of the Upper Ordovician in the Cincinnati Arch region USA: the early history of light-related microendolithic zonation. Palaeogeography, Palaeoclimatology, Palaeoecology 281: 1-24.

Wilson, M.A. and Taylor, P.D. 2017. Exceptional pyritized cyanobacterial mats encrusting brachiopod shells from the Upper Ordovician (Katian) of the Cincinnati, Ohio, region. Palaios 32: 673-677.

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