Can Heat Flow in Ocean Models Predict Seasonal Arctic Sea Ice Retreat?

August 8th, 2018

Note: The following blog post is by Ben Sershen (’19), who worked with Dr. Crawford on a summer research project.

Source: https://csmphotos.wordpress.com/2013/01/17/bering-sea-opies-and-the-reality-of-the-deadliest-catch/

Intro: My summer research work aimed to further my Junior I.S. in the fields of oceanography and climatology. My research question was: “How well do computer ocean models work for predicting the melt of Arctic sea ice?” This is an important question to ask because many companies are looking to use the Arctic as a shipping passage. To answer this question, I analyzed the data from two models: The Simple Ocean Data reanalysis (SODA) and the Ocean ReAnalysis System 4 (ORAS4), which was produced by the European Center for Medium-Range Weather Forecasts (ECMWF). SODA and ORAS4 are programs that uses physics as well as real-world data, such as from underwater moorings, automated Argo floats, and satellites, to estimate aspects of the oceans such as temperature, water velocity, and salinity. These data could then, in theory, be used to determine when the enough heat has entered the Arctic Ocean to melt sea ice each year.

 

Figure 1: (Left) A map of the Bering Strait with the A3 mooring location labeled. The Chukchi Sea is the area to the north (above) the strait. The magenta line represents the location of my study. (Right) A similar map of the Bering Strait with the Alaskan Coastal Current (ACC) and the Siberian Costal Current (SCC) represented by the red and blue arrows, respectively (Woodgate et al., 2015).

Methods: I focused on the Bering Strait/Chukchi Sea region. This area is important as it is the strait where warm water enters the Arctic, as seen in the second map in figure 1. I calculated how much heat was passing through the Bering Strait, into the Arctic using data from SODA and ORAS4. Once I had done this, I had to compare my results to the data from the A3 mooring. This was done by first performing simple correlations (when the heat flow increases do the mooring temperatures increase?). I then correlated the heat flow values to sea ice data – more specifically, the date of the year when the sea ice concentration in the Chukchi Sea dropped below 30%. As heat flow increases, the ice melts faster, retreating earlier. To be a good predictor of sea ice retreat, the heat flow from the models must show this relationship (a positive correlation between the amount of heat and the rate of ice melt).

 

Figure 2: An example of a cross-section contour plot through the Bering Strait. The darker red represents more heat traveling through the cross-section at that location. The location of the cross-section is marked by the magenta line on the left map in figure 1.

Results: I found that SODA was only accurate when there were mooring data being fed into it. That meant that SODA would not do a very good job at predicting future ocean heat because it relied heavily on real-world data. I performed the same data analysis of ORAS4 that I had performed on SODA and found that ORAS4 produced data that was closer to the mooring data even when mooring data was not available. The ORAS4 data also had a stronger correlation with the sea ice data. I would guess that this is because the ORAS4 is simply better than the SODA model generating realistic data. The ORAS4 model focused on tropical data to generate data and produced better data than SODA, which had a bit more of an Arctic focus. I think that result goes to show how interconnected the world’s oceans really are if you can make accurate predictions of the temperature of the Arctic Ocean from data produced by a tropical model. Using the monthly heat flow values from ORAS4, I created a heat map to visualize the data (figure 3).

Figure 3: A heat map of heat flow data from ORAS4. The y-axis represents months of the year. Note the warmer values occurring in June-October. This represents the seasonal cycle. The x-axis represents years 1990-2017 which illustrates substantial interannual variability.

 

References

Last day at the Tartu Natural History Museum, and a visit to a grim museum

August 7th, 2018

Tartu, Estonia — Bill Ausich and I started our last full day in this city at the University of Tartu Natural History Museum, finishing our work with the marvelous Mare Isakar, pictured above. Mare quickly found the specimens we needed, and many others she knew we would find interesting. She did nearly instant registration of specimens, greatly speeding up our taxonomic progress.

We finished photographing museum specimens for our future reference and possible publications. Bill concentrated on Silurian crinoids and I worked on the Ordovician rhombiferan Echinosphaerites.

This is one of Öpik’s Echinosphaerites aurantium specimens. Two roundish encrusting brachiopods are visible, along with sheet-like bryozoans. Shockingly, there are gouges in the bryozoans as if someone tried to scrape them off!

Most of the rhombiferans are filled with sediment and/or calcite crystals, but Bill found this hollow one in the collections. Note that it was still able to resist sedimentary compaction. Also note the bryozoans on the broken edge.

This broken specimen shows sediment in the bottom of the skeleton and crystals in the top half. This is known as a geopetal structure where the sediment shows what was the lower part of the skeleton when it was filled. Here’s another example.

Mare found even more specimens of Echinosphaerites today, so there is much to do on a later trip! Thank you again to Mare Isakar and our other friends in Tartu. Tomorrow we travel to Tallinn for a bit more work before heading home on Friday.

And now for something darker — the KGB Cells Museum in Tartu. It is a horrifying place of pain, anguish and hopelessness, yet today is surrounded by a vibrant, free city and country. This museum, in an actual KGB prison, is both disturbing and ultimately inspiring. It is a history we avoid at our peril.

A cell door near the entrance to this basement complex of “the grey house”. These dungeons were used by the Soviet secret police for detention, torture and executions in the 1940s and 1950s. For a brief interval (1941-1944) the Nazis took over and did the same beastly activities. The victims were almost entirely Estonians.

A hallway of cells. The exhibits inside the rooms include many Soviet artifacts, along with stories of Estonian resistance.

A KGB mannikin at the end of a hallway. A sound track of a harsh Russian voice plays in a loop here, along with inevitable screams and moans. The brutality of the place is quite evident enough, thank you.

Finally, before you leave, why not dress up as a Soviet KGB officer and pose with Stalin? I don’t understand why anyone would do such a thing, especially in such a tragic space.

Tomorrow it is back to science as Bill and I take the bus to Tallinn. The countryside of free Estonia is beautiful.

Last day in the University of Tartu Geology Department — and a great garden party

August 6th, 2018

Tartu, Estonia — As a sign we’re near the end of our work in Tartu, there are no crinoids in this post. Instead, above is an Ordovician bryozoan from Estonia that encrusted the aragonitic shell of a nautiloid. The aragonite dissolved away, giving my favorite underside view of a bryozoan attachment from its ancestrula. We’ve seen this more than once in this blog. The bonus here are the just-visible chains of little crystalline teardrops across the surface.

These are the zooids of the cyclostome bryozoan Corynotrypa. They are encrusted right-side-up, meaning that they grew across the exposed attachment surface of the big bryozoan. The nautiloid shell thus dissolved between the two encrusting events — very early on the seafloor. Classic calcite sea dynamics.

After sorting out the specimens used in our crinoid studies, and doing some last microphotography, we finished our work for this season at the University of Tartu Department of Geology. A small and happy garden party followed.

Bill Ausich and some of our Estonian colleagues and friends. From the left is Oive Tinn, Mare Isakar, Bill, and Viirika Mastik. Great conversations. It actually got a little chilly outside, so we ended in Oive’s house (see below).

Sunday at the University of Tartu Natural History Museum — this time as tourists

August 5th, 2018

Tartu, Estonia — Bill Ausich and I returned to the Natural History Museum today to tour the public exhibits. It was hard to not make it into a study trip, though, for our research. I suppose since our “work” is so enjoyable it is difficult to separate it from a holiday. Above, for example, is a display of our favorite rhombiferan, Echinosphaerites aurantium of the Estonian Upper Ordovician.

There is a display about the Kalana Lagerstätte that we are studying.

Here is the museum description of the Lagerstätte.

And a close-up of some crinoids (“meriliilia”, sea lilies) from the Kalana.

It is a fun museum with a very thorough geology section, including meteorites you can touch (a favorite of mine). It has what is now an old-fashioned style of emphasizing actual specimens that Bill and I appreciated. There is a large biology section with much taxidermy and mounted skeletons. One of the featured exhibits is a rare “rat king” (see below), which you must look up!

Saturday at the Estonian National Museum (plus a street festival)

August 4th, 2018

Tartu, Estonia — This morning Bill Ausich and I walked to the new Estonian National Museum, shown above. It has a most unusual elongated building constructed on an abandoned secret Soviet airbase for bombers (Raadi Airfield). It follows an old runway with the revetments still in place. It is striking.

Parts of the Soviet base are still preserved, including these concrete fence posts.

This is an old Soviet air force garage on the way to the museum. This base was so secret that the entire city of Tartu was closed to foreigners. Now Bill and I stroll the grounds. We did the same in a once-secret Soviet missile base on Saaremaa.

The front entrance of the Estonian National Museum.

I don’t have a lot to show you in the museum itself, since it is mostly about fold and cultural history (which was fascinating). Bill and I appreciated the digital signs. They appear first in Estonian, like this one. We were issued special language cards, though.

When we pass the “English” card across the sensor, the text is instantly translated! Very clever.

Across the road from the museum is an upside-down house. It is apparently quite the tourist attraction, but we passed.

Back in the city center, in fact in front of our hotel, was a street festival. It had live music, fantastic food, and large, happy crowds.

There were lots of fried fish stands, with fish from the local lakes and the Baltic.

Here is Bill waiting for a meal. Impressively, by 10 pm the festival was over, and the streets completely clear the next morning. This is a very efficient, sensible country!

Back to work in the University of Tartu Geology Department

August 3rd, 2018

Tartu, Estonia — Today Bill Ausich and I returned to the geology lab on the university campus to continue our work on the Kalana Lagerstätte crinoids. There is Bill above working on specimens.

I spent most of the day working with this beautiful Leica photomicroscope (model S9i). It is the most intuitive photomicroscope I have ever seen. The images are superb. I want.

Here I am at the microphotography station, looking wistfully outside.

We don’t have anything new to report today, so here’s an image of one of the best Kalana crinoids.

This is my favorite specimen because it is squashed in a way that separated the calyx plates to make them easier to see.

The calyx is on the left side of this specimen. The pinnules from the arms are preserved so well here they look like hair. Note the small angular fossil just below the crinoid on the right. These are common in the Lagerstätte, often appearing to be attached to crinoids. We think they may be green algae, possibly like the modern Hydrodictyon but marine — and with larger cells. Another mystery in this fossil assemblage.

We’ve now completed a week in Tartu. The Kalana crinoid project has gone especially well. Thank you to graduate student Viirika Mastik who collected most of the Kalana crinoids, and to her supervisor Oive Tinn. They have helped us immensely in the lab.

Starting work in the University of Tartu Natural History Museum

August 2nd, 2018

Tartu, Estonia — Today Bill Ausich and I began our work in the University of Tartu Natural History Museum. Our most knowledgeable and helpful host is chief geology curator Mare Isakar. This museum is just a short walk from our hotel.

This is one of the collections rooms in the paleontological research part of the museum. Here is where I examined Ordovician bivalves and gastropods for bryoimmurations.

One of our goals is to study encrusters on specimens of the nearly spherical Late Ordovician rhombiferan echinoderm Echinosphaerites aurantium. Mare Isakar kindly set out dozens of specimens for us to study, a small subset of which is shown above.

Here is Bill at work scanning through a drawer of Echinosphaerites.

One of the encrusted Echinosphaerites skeletons. The black, branching, carbonaceous encruster is the graptolite Thallograptus sphaericola (“sphere-dweller”).

Posted in the museum is this figure by Öpik (1925) showing his idea of an Echinosphaerites community with encrusting graptolites. We want to test his hypothesis that the graptolites encrusted living rhombiferans as shown. My hypothesis is that the graptolites lived instead on dead, cemented skeletons. Armin Aleksander Öpik (1898-1983) was a prominent and productive Estonian paleontologist. Like many Estonian scientists of his generation, his career was bifurcated by World War II.

Several characters from Estonia’s scientific past watched us work. This is Constantin Grewingk (1819-1887). Ohio paleontologists will recognize him as the namesake of the rugose coral Grewingkia.

Here is Friedrich Schmidt (132-1908), considered the founder of Estonian geology. Both Grewingk and Schmidt were Baltic Germans.

The public part of the museum includes this exhibit on “Secrets of Ancient Sea”. You may recognize some familiar Ordovician characters in this scene. Bill and I intend to visit the public exhibits here on Sunday.

Thank you again to Mare Isakar for setting us up so efficiently for our research!

Back to the paleontology lab in Tartu, Estonia

August 1st, 2018

Tartu, Estonia — Disconcertingly it says “chemistry”, but there really is a geology department inside this building on the University of Tartu campus.

The Geology Department is part of the Institute of Ecology and Earth Sciences. We are very impressed with their facilities and friendly academics.

Here again is the lab room loaned to us for our stay. Bill is working in the back. The crinoid-rich specimens from the Kalana Lagerstätte at the Kalana Quarry (Silurian, Llandovery, Aeronian) are spread out through the room. We are very fortunate to have such space.

This is my workstation with my trusty laptop. The Leica microscope is fantastic.

We are examining the crinoids preserved on this dolomicritic limestone slabs that were carefully collected by university staff from Kalana Quarry in central Estonia. The crinoids are quickly apparent because their beautiful hair-like pinnulate arms are visible.

I’ll write more paleontological details later, but here is the part-counterpart of the best specimen of what will be a new crinoid taxon. From the bottom is the cylindrical stem, followed upwards by the conical calyx, and then the long arms with thin extensions called pinnules. You can also see some black smears of carbonaceous material on the right. These specimens are compressed and mostly decalcified. Their preservation is still a bit mysterious to us.

This is why we’re here so far from home!

Here is an image of the Kalana Quarry, where the Lagerstätte is found, from this wonderful Estonian geology website.

Fieldwork in Estonia, with a bonus visit to Narva

July 31st, 2018

Tartu, Estonia — Today Bill and I had a spectacular geology and culture field trip in northeastern Estonia. As you can see in the images, the weather was excellent, if a little warm. Our Estonian hosts took us from Tartu to several places north and east to the border with Russia. Our fieldwork in an oil shale quarry is shown above, but first our journey there —

Lake Peipsi (or Lake Peipus) is near Tartu. It is one of the largest freshwater lakes in Europe, with the Russian border running down its center. We stopped briefly for this view. It looks like one of North America’s Great Lakes from here. There is much history along these shores.

This is the Kiviõli Concentration Camp Holocaust Memorial near our collecting site today. The 20th century history of this region, especially during World War II, is notably grim and brutal. Relatively little has been published on the German concentration camps in Estonia.

This is the oil shale mine we visited near Põhja-Kiviõli in northern Estonia. The oil shales, in the form of kukersite, are the brown units in the top half of the outcrop. The shales are dug from these pits and then separated from the limestones, which appear light gray. The pits fill quickly with water, so there are massive pumps continually working nearby.

A closer view of an oil shale outcrop. These units are Late Ordovician in age (Sandbian) and nearly unique to Estonia. They are very rich in organic material — up to 55% of the rock. The oil shales are used in a variety of ways for energy and petroleum products.

Finding specimens of the spherical rhombiferan echinoderm Echinosphaerites was one of our goals for this trip. Here is one in limestone. The best are those that are in the oil shale because they pop free of the matrix. We didn’t find very many, though.

Giant bryozoans were surprisingly common in the oil shales. This is the base of a large trepostome. We found many of these bryozoans with beautiful borings. It was a good collecting site.

Here are our delightful Estonian hosts at lunch following fieldwork. From left to right: Olev Vinn (a colleague since 2006), Ingrid Vinn, and Mare Isakar.

Much to our surprise we were able to go to the storied easternmost Estonian city of Narva. This was very much a treat. Narva sits along the Narva River, which is the border with Russia. The city has a high concentration of Russian-speakers and a distinct Estonian-Russian culture. Its history has been, needless to say, complex even to present times.

This is Hermann Castle, also called Narva Castle, the focus of our visit. Hermann Castle is the blocky, high structure. To the right is visible another castle on the other side of the Narva River (see below).

This is that Russian castle opposite the Hermann Castle on the castle on the other bank of the Narva River. It is the Ivangorod Fortress. It makes for quite a striking boundary at the western edge of Russia.

The Narva River between the two castles, looking upstream. The Ivangorod Fortress is on the left. This is effectively the boundary between East and West in Europe.

The Narva border crossing bridge between Estonia on the left and Russia on the right. This is the view from the top of the Hermann Castle. At this point my phone gave me a message: “Welcome to the Russian Federation”.

The interior of the Hermann Castle is a museum. I thought these stone cannon balls were geologically interesting, considering that earlier this summer I saw their equivalents in Wales. Note my foot for scale.

On the way back to Tartu, we visited the town of Sillamäe on the Baltic coast. During Soviet times factories in Sillamäe extracted uranium oxides from local oil shales and then from other ores mined throughout the Soviet Empire. Because of the high concentration of scientists and engineers, this town was built with, shall we say, higher architectural and aesthetic standards than the usual Soviet constructions. It was a “closed town” forbidden to foreigners or even most Estonians.

This is a 1987 statue in Sillimäe celebrating its atomic achievements. By then this town produced almost 100,000 tons of uranium oxides for Soviet nuclear weapons and energy plants. It all stopped in 1989, and when Estonia reclaimed the area two years later there were serious contamination problems to solve. [Update: Cheryl Rofer, Los Alamos National Laboratory (retired), added a comment and a link to her story about the clean-up: Averting a Baltic Sea Disaster. It is an excellent read!)

What a rich trip this was. Thank you again to Olev, Ingrid and Mare.

Starting work in Estonia

July 30th, 2018

Tartu, Estonia — Ah, fossils at last! Bill Ausich and I are here to explore several topics, but the main one is describing the crinoids in a Silurian (Aeronian) Konservat Lagerstätte at Kalana Quarry in central Estonia. Much more on this later, but above is one of the crinoids, from the stem to the calyx to the pinnulate arms. The preservation is very odd, with most of the original calcite dissolved away and considerable carbonization and, maybe, some recrystallization. (Much of the list of preservation modes we teach!)

We’re working in a beautiful teaching lab at the University of Tartu. We have plenty of space to lay out the specimens collected by the geologists here. (These particular quarry beds are no longer accessible.) The microscopes are new and the best student models I’ve seen.

Today was mostly orientation for us in the lab. After dinner we walked down to the Emajõgi River, which runs through the campus and has been very important in Estonian history. Its name means “Mother River”. Beautiful.

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