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And now…

Chasing Microbes in Antarctica - Wed, 09/16/2015 - 00:24

…for something completely different.  My wife and I are expecting our first child in a few months, which is wonderful and all, but means that we are faced with the daunting task of coming up with a name.  Being data analysis types (she much more than me), and subscribing to the philosophy that there is no problem that Python can’t solve, we decided to write competing scripts to select a good subset of names.  This is my first crack at a script (which I’ve titled BAMBI for BAby naMe BIas), I’ve also posted the code to Github.  That will stay up to date as I refine my method (in case you too would like Python to name your child).

My general approach was to take the list of baby names used in 2014 and published by the Social Security Agency here, bias against the very rare and very common names (personal preference), then somehow use a combination of our birth dates and a random number generator to create a list of names for further consideration.   Okay, let’s give it a go…

First, define some variables. Their use will be apparent later.  Obviously replace 999999 with the real values.

get = 100 # how many names do you want returned? wife_bday = 999999 my_bday = 999999 due_date = 999999 aatc = 999999 # address at time of conception size = (wife_bday + my_bday) / (due_date / aatc) start_letters = ['V','M'] # restrict names to those that start with these letters, can leave as empty list if no restriction desired sex = 'F' # F or M

Then import the necessary modules.

import matplotlib import numpy as np import matplotlib.pyplot as py import math import scipy.stats as sps

Define a couple of variables to hold the names and abundance data, then read the file from the SSA.

p = [] # this will hold abundance names = [] # this will hold the names with open('yob2014.txt', 'r') as names_in: for line in names_in: line = line.rstrip() line = line.split(',') if line[1] == sex: if len(start_letters) > 0: if line[0][0] in start_letters: n = float(line[2]) p.append(float(n)) names.append(line[0]) else: n = float(line[2]) p.append(float(n)) names.append(line[0])

Excellent. Now the key feature of my method is that it biases against both very rare and very common names. To take a look at the abundance distribution run:

py.hist(p, bins = 100)

figure_1Ignore the ugly X-axis.  Baby name abundance follows a logarithmic distribution; a few names are given to a large number of babies, with a long “tail” of rare baby names.  In 2014 Emma led the pack with 20,799 new Emmas welcomed into the world.  My approach – I have no idea if it’s at all valid, so use on your own baby with caution – was to fit a normal distribution to the sorted list of names.  I got the parameters for the distribution from the geometric mean and standard deviation (as the arithmetic mean and SD have no meaning for a log distribution).  The geometric mean can be calculated with the gmean function, I could not find a ready-made function for the geometric standard deviation:

geo_mean = sps.mstats.gmean(p) print 'mean name abundance is', geo_mean def calc_geo_sd(geo_mean, p): p2 = [] for i in p: p2.append(math.log(i / geo_mean) ** 2) sum_p2 = sum(p2) geo_sd = math.exp(math.sqrt(sum_p2 / len(p))) return(geo_sd) geo_sd = calc_geo_sd(geo_mean, p) print 'the standard deviation of name abundance is', geo_sd ## get a gaussian distribution of mean = geo_mean and sd = geo_sd ## of length len(p) dist_param = sps.norm(loc = geo_mean, scale = geo_sd) dist = dist_param.rvs(size = sum(p)) ## now get the probability of these values print 'wait for it, generating name probabilities...' temp_hist = py.hist(dist, bins = len(p)) probs = temp_hist[0] probs = probs / sum(probs) # potentially max(probs)

At this point we have a list of probabilities the same length as our list of names and preferencing names of middle abundance. The next and final step is to generate two pools of possible names. The first pool is derived from a biased-random selection that takes into account the probabilities, birth dates, due date, and address at time of conception. The second, truly random pool is a subset of the first with the desired size (here 100 names).

possible_names = np.random.choice(names, size = size, p = probs, replace = True) final_names = np.random.choice(possible_names, size = get, replace = False)

And finally, print your list of names! I recommend roulette or darts to narrow this list further.

with open('pick_your_kids_name.txt', 'w') as output: for name in final_names: print name print >> output, name

A Week of Firsts for This Arctic Nation

TRACES of Change in the Arctic - Fri, 09/11/2015 - 18:06
47 AM the ship reached the North Pole, becoming the 1st U.S. surface vessel to do so unaccompanied. (photo U.S. COAST GUARD)

Gathered at the North Pole are the crew of U.S. Coast Guard Cutter Healy and the GEOTRACES science team. On Sept. 5 at 7:47 a.m., the ship reached the North Pole, becoming the first U.S. surface vessel to do so unaccompanied. Photo: U.S. Coast Guard

We are closing in on a week of intense focus and excitement for GEOTRACES and for the United States around the Arctic. It was barely a week ago (Aug. 31) that President Obama became the first sitting president to visit Alaska, refocusing the other 49 states on the fact that we are indeed an Arctic Nation. This historic first was followed closely by another, the Sept. 5 arrival of the U.S. Coast Guard Cutter Healy with the U.S. GEOTRACES scientists on board at the North Pole, completing the first U.S. surface vessel transit to the pole unaccompanied by another icebreaker. Combined with this, U.S. GEOTRACES became the first group ever to collect trace metals at the North Pole. You might assume these three items are unrelated, but they are in fact tightly linked.

GLACIER Conference logo

GLACIER Conference logo

In convening the GLACIER Conference (Global Leadership in the Arctic: Cooperation, Innovation, Engagement & Resilience) in Alaska, President Obama focused on a region that is fast changing due to its fragility and vulnerability to climate change. The meeting timing aligned nicely with the U.S. assuming chairmanship of the Arctic Council, and was a perfect platform for the president to address climate change, an issue that he has tackled aggressively. Conference sessions on the global impacts of Arctic change, how to prepare and adapt to a changing climate, and on improved coordination on Arctic issues all align with the work of Arctic GEOTRACES, although tackled from a different angle.

It was while he was in Alaska that President Obama announced a commitment to push ahead the schedule for adding to the U.S. icebreaker fleet. The “fleet” has dwindled to just 3 U.S. vessels at present, and limits our ability to work in the Arctic. The goal of adding another icebreaker by 2020 will help to address this. “Working” in the Arctic for this Coast Guard cutter includes supporting the research that is critical to our being able to develop a baseline understanding of conditions and more accurately predict the future changes.

Ship camera as the US Cutter Healy arrives at the North Pole. (Photo US Healy)

Ship camera as the U.S. Cutter Healy arrives at the North Pole. Photo: U.S. Healy)

Evidence for change in the Arctic is found in the ability of the U.S. Coast Guard Cutter Healy to cross the Arctic ocean along its longest axis (the Bering Strait route) and penetrate deep into the sea ice to make it to the North Pole unaccompanied. The ice has been thinner than expected and experiencing a much higher degree of melt. Ice stations, where the science team gets out onto the ice to sample, have been postponed because of safety concerns from the thin ice conditions. Everyone, including the captain, has been surprised by the conditions. The thin ice has increased the speed of travel. Although some thick (up to 10 feet) and solid ice has been encountered, much of the cruise has been spent traveling at up to 6 knots, and much less fuel has been used than expected because of this.

Members of the team who are not out on deck with the equipment 'manage' the cast from the aft control room. (photo T. Kenna)

Members of the team who are not out on deck with the equipment “manage” the cast from the aft control room. Photo: T. Kenna

The last week has been action packed for all 145 people on the Healy. First. a “superstation” was run, a 57-hour sampling stop with a large number of samples collected in the ~4,000-meter-deep water. A super station includes additional hydrocasts and pump sampling for the groups like Tim Kenna’s, that require large volumes of sample water. This was also a crossover station with the German GEOTRACES cruise on the Polarstern. Crossover means some of the extra samples collected can be used to do intercalibration (check to see that the results compare) between the science teams on the two ships. The German ship will collect at the exact same location. With large sampling projects using multiple labs and sampling teams, intercalibration becomes extremely important for interpreting the results.

The 'man-basket' lowering Tim Kenna and crew member to the ice via crane to do sampling from a pressure ridge. (photo Bill Schmoker)

The “man-basket” lowering Tim Kenna and crew member to the ice via crane to do sampling from a pressure ridge. Photo: Bill Schmoker

After our long superstation, the team went almost immediately into a dirty-ice station (ice that entrains sediment as it freezes). This ice can form in several ways: during the spring thaw when ice dams in Arctic streams force sedimented water out onto the ice, where it refreezes; during cold storms that churn up sediments in the shallow shelf regions to refreeze on the surface ice; and when shallow areas freeze solid, collecting sediment at the base, and later break away. Once the ice is formed, it moves into the Arctic circulation pattern, so identifying the source of the sediment can help us better understand the temporal and spatial nature of Arctic circulation. This type of ice has high value for Tim’s research, since short-lived radioactive isotopes are frozen into the ice with the sediments, providing a timer for the formation of the ice.

The dirty ice station was followed by an ice-algae station. Both of these entail stopping the ship and craning over two people in a “man-basket” where they can get out and sample (see image). This was followed closely by two full ice stations, where many groups went out on the ice to do their sampling; some for over 12 hours (brr). The second ice station had wind chills of -14 C.

Field time, especially in the polar regions, is expensive and limited, so while in the field it is critical to complete as much science as possible. Sleep happens later when the team is back home.

Lamont Note: As part of the Healy’s instrument package, they standardly carry a CO2 instrument from Lamont’s Taro Takahashi. This was onboard when the Healy reached the North Pole (89.997 °N). The partial pressure of CO2 (pCO2) in seawater was found to be 343.3 micro-atmospheres at the water temperature of -1.438 °C. This is about 50 micro-atmospheres below the atmospheric pCO2 of 392.7 micro-atmospheres, and indicates that the Arctic Ocean water is rapidly absorbing CO2 from the air. The measurements confirm that the Arctic Ocean is helping to slow down the accumulation of the green house gas in air and hence the climate warming.

Margie Turrin is blogging for Tim Kenna, who is reporting from the field as part of the Arctic GEOTRACES, a National Science Foundation-funded project.

For more on the GEOTRACES program, visit the website here.

Habitat

Geopoetry - Fri, 09/11/2015 - 12:00
The Island of Manhattan. Image from the Wildlife Conservation Society

Images representing the past and present Island of Manhattan. Credit: Wildlife Conservation Society

 

People are sometimes startled

By falcons perched on balconies, raccoons slinking through the park,

Bluefish blitzing herring up the river, coyotes tracing train tracks.

Isn’t it amazing, or isn’t it disturbing, we say,

A creature’s daring foray into our hard-paved empire.

I prefer the long view – that of Manhattan Schist, let’s say,

Having been buried in mile-thick ice,

Thoroughly sculpted and scoured,

Recolonized by green things and red-blooded things

Over and over again, with each ephemeral ice age.

From that vantage, it is we who are the curious invaders, an encrusting colony

Of organisms with a stunning talent for creating habitat for ourselves.

Diggers of ditches, un-earthers of bones, surveyors of history

All tell a tale of an earlier island of Eden,

Teeming with silver-backed, feather-tipped, vibrant-green life

Not so long ago.

The Schist, sparkling darkly in the park, is not surprised

By ‘coons and hawks, toothed and clawed neighbors,

Nor by the eels, pipers, moths, terrapins, raptors, seals, spiders,

By great trees ripping upwards through pavement.

You might think that I am about to lament all the changes we have wreaked

On this landscape, but I refuse to despise my own species.

I refuse to accept the conservationist’s guilt,

To draw boxes around wildness and around civilization,

And ignore the reality that these two can never truly be separated.

Instead, I am in awe of the spectacular forces that shape my world,

From grinding ice sheet to pulverizing jackhammer,

From rising skyscraper to ascending oak.

I live my animal life deliberately,

Knowing that we can never extract ourselves from Nature,

And that the boundaries we draw are not real.

 

This is one in a series of posts by Katherine Allen, a researcher in geochemistry and paleoclimate at the Lamont-Doherty Earth Observatory and the School of Earth & Climate Sciences at the University of Maine.

It’s as Clear as Mud

TRACES of Change in the Arctic - Sun, 09/06/2015 - 21:30
Core sample

Attempting to get a small sediment sample from the bottom of the Arctic. Photo: Bill Schmoker

Sediment coring the bottom of the world’s oceans is something that Lamont knows a lot about. Since 1947 Lamont has been actively collecting and archiving sediment from around the world. Currently our Core Repository contains sediment cores from every major ocean and sea in the world, some 18,700 cores. This is in large part due to Lamont’s first director, Maurice Ewing, who instilled a philosophy of “a core a day” for all ocean research vessels. Ewing firmly believing that if we had the sediment, we would be able to piece together patterns and stories about our planet, so every day at noon, or thereabouts, the ship would collect a core.

core repository

Historic Image of Lamont’s Core Repository. Photo: Lamont archive

Scientists from around the world have requested slivers of mud from the cores in the repository to unlock Earth’s mysteries and secrets. The cores in Lamont’s Core Repository are no stranger to revealing stories of Earth systems, including those of climate cycles. Almost 40 years have passed since the groundbreaking work of the CLIMAP group that used the cores to connect the start of Earth’s glacial cycles to changes in eccentricity, precession and tilt. (Hayes, Imbrie and Shackleton, 1976) . Collecting sediment on this Arctic GEOTRACES cruise will help us understand more of the stories locked in the oceans.

The length of a core is dictated by the goal of the collection. Early Lamont cores were more about collecting just to gather the material because the ship was there. These early cores were generally 6 to 9 meters long, although one incredibly long 28.2m core was collected from the Central Pacific. Locally cores have been collected on the Hudson River and local marshes that are closer to 1 or 2 meters in length.

Coring in the Hudson River

A file photo of Tim Kenna collecting a sediment core from the Hudson River. Note the length of core and the heavy weights on top to help with penetrating deep into the mud on the bottom of the Hudson. The very short cores to be collected for GEOTRACES will be much different. Photo: Margie Turrin

For the sampling GEOTRACES is doing in the Arctic, there is a specific goal of collecting just the top few dozen centimeters of sediment and the water just above it, yet at a depth of ~2,200 meters. This will require a much different technique than what was used for the Central Pacific core.

core

Mono-corer with the small section of core retrieved. Note the small weights to help penetrate the sediment, much less weight than is used on the Hudson River core pictured above. Photo: Bill Schmoker

The sediment in this region is soft, so the plan was to drop a small, general-purpose device called a mono-corer over the side of the ship with a few small weights on top to help drive the core tube in straight. The corer would hang below the bottom of the rosette of water samplers, far enough below that the rosette would remain mud-free but still able to collect near-bottom water samples. The mud in the mono-corer would be held in place by a spring-loaded door that snapped closed once the mud was inside and the tube began its return trip to the ship. All sounded good.

core

Core on its way up to the Healy. Note the “cone-of-silence” rigged by Tim Kenna and Marty Fleicher to stop any interference with the rosette altimeter used to lower the device. Photo: Bill Schmoker

Although the plan was good, things don’t always go perfectly. Making sure the corer actually penetrated the sediment without tipping over or over-penetrating and compressing the top sediments proved challenging, as did ensuring the sample made it back to the ship intact. After several attempts a special “cone-of-silence” (any Get Smart fans out there?) was rigged up by the two Lamonters, Tim and Marty Fleischer, to avoid interference with the communications that were connecting with the rosette altimeter, controlling the lowering of the device. The cone was installed and the speed of the core lowering was slowed. Success! ‘Houston we have mud!’

Now to unpack its secrets.

Margie Turrin is blogging for Tim Kenna, who is reporting from the field as part of the Arctic GEOTRACES, a National Science Foundation-funded project.

For more on the GEOTRACES program, visit the website here.

Scouring Arctic for Traces of Fukushima and Cosmic Rays

TRACES of Change in the Arctic - Sat, 08/29/2015 - 21:50
ice breaker

The Healy is doing a lot more ice breaking now that we have moved into the Arctic ice cap. Photo: Tim Kenna

Sounds like the basis for a great scifi thriller… “scientists scour Arctic, hunting for traces of nuclear fallout and ejections from cosmic ray impacts.” In reality this thriller theme is the actual core of the GEOTRACES mission. Let’s break it apart a bit to better understand it.

Fukushima and Other Nuclear Fallout

The project Tim is focused on is the human introduced (anthropogenic) radionuclides that are released into the environment as a result of nuclear industrial activities, things like weapons production and testing, as well as nuclear power generation and fuel reprocessing. This includes isotopes of plutonium, neptunium, cesium, strontium, iodine and uranium that are not normally found in the environment. The major sources of these nuclides include fallout from atmospheric weapons testing and liquid releases from European nuclear fuel reprocessing.

Radionuclides lab

The workspace set aside for the radionuclides work. If you have ever done “Where’s Waldo?” see if you can find Tim’s spot. Photo: Tim Kenna

One goal of our project is to determine the budgets (overall input and export) of these contaminants. Samples collected along our cruise track combined with those collected on the European GEOTRACES cruise taking place on the Polarstern will allow us to do this.

We are also collecting samples to evaluate for the presence and distribution of contamination related to Fukushima. Two cesium isotopes were released into the environment as a result of Fukushima; Cesium 137, with a half-life of 30 years, and Cesium 134, with a much shorter half life of two years, so little is left from past nuclear testing. Fallout from Fukushima is an excellent tracer to help us learn more about ocean circulation and transport models.

Cosmic Ray Interactions

Paul Aguilar

Paul Aguilar, part of the Beryllium 7 sampling team, signals thumbs up to the winch operator on a hydrocast. Hand signals are a major method of communication between ship operators and scientists and crew on deck. Photo: Tim Kenna

Another part of the GEOTRACES team is measuring Beryllium-7 (Be-7), a cosmogenic nuclide that is created when a cosmic ray breaks apart heavier atoms into smaller atoms. Be-7 is a short-lived isotope with a half-life of 53 days. We can use this short half-life to tell us something about water circulation and exchange rates under the ice. Currently the team is measuring Be-7 in the marginal ice zone. Once the ship reaches a section of ice that is large and thick enough for the scientists to work on, we will drill through to measure under the ice as well.

Yes We Have a Bubble Room!

bubble room

Jess and Sarah work in the heavily protected bubble room to keep their samples from being contaminated by elements on the ship. Photo: Tim Kenna

When we said “trace” elements we weren’t kidding! Jess and Sara are part of the team working on contamination-prone trace elements. Their work is done in an inflatable bubble to keep it ultra clean. The bubble is inflated using high-efficiency particulate arresting (HEPA) filtered blowers. Trying to measure very small trace elements without contamination is extremely difficult, and it is a testament to their skills that they can measure elements such as zinc and iron, which are extremely low in seawater but very common on the ship (rust never sleeps!). Getting an accurate measure means not picking up any of that ship input.

caught wires

Sampling in and among the ice floes can mean equipment wires get caught on the ice, as happened here. It can be tricky to untangle caught wires to free equipment. Photo: Tim Kenna

In order to run all these great experiments, we need samples, so we are collecting and filtering water at as many stations as we can. Sampling in the ice pack is very different than sampling in an open ocean. Station locations must be very carefully selected to reduce the risks of the equipment getting entangled in the ice and ending up either crushed or ripped away. Even in less dense ice, we caught the hydrowire on an ice floe (above).

Supersized

Everything is supersized on a ship like the Healy, from the large metal A-frame support that is used to lower collection equipment (yellow/buff colored) to the circular metal rosette which is filled with niskin collection bottles for gathering water samples. The deployment of a rosette for sampling is called a “hydrocast.” This allow scientists to collect water at a variety of depths. The images below are from a few days ago, before we hit denser pack ice.

hydrocast

You can see if you look carefully at the photos that these bottles have snapped closed, sealing the water sample inside. When deployed the bottles are opened at both ends so water freely flows through as the rosette descends to the sample depth. Photo: Tim Kenna

The rosettes can hold up to 36 bottles. Each bottle can be programmed to snap closed at a specific depth, so in one deployment, water can be collected at up to 36 different depths. This is extremely valuable for teasing apart circulation through tracking small particles entrained in the water column at different depths. The water collected in these sampling bottles will be used for a range of studies.

hydrocast

The rosette takes several people to stabilize and guide it over the side of the ship, and the A frame is several stories high. Photo: Tim Kenna

This sequence of the retrieval of this hydrocast involves four people to collect and stabilize the rosette, as well as the personnel up above operating the winch to lower the equipment, and several people in a console monitor verifying both the depth of the rosette and that the cable on the equipment is sending up the necessary data. Operating the equipment on a ship is labor intensive, but each deployment retrieves enough sample material for not only the team on board the Healy, but for colleagues and partners waiting back at their home institutions for samples.

Margie Turrin is blogging for Tim Kenna, who is reporting from the field as part of the Arctic GEOTRACES, a National Science Foundation-funded project.

For more on the GEOTRACES program, visit the website here.

 

Moving into the Realm of the Polar Bear

TRACES of Change in the Arctic - Mon, 08/24/2015 - 18:15
Looking out over the Arctic sea ice as the ship moves out over the deeper ocean. (Photo credit Tim Kenna)

Looking out over the Arctic sea ice as the ship moves out over the deeper ocean. Photo: Tim Kenna

The Healy has now moved off of the shallow continental shelf that extends around the Arctic land border (shown in white in the map below) into the deeper center of the Arctic Ocean. In our last blog we noted that some of the questions Arctic GEOTRACES is addressing include quantifying the fluxes of trace elements and isotopes into and out of the Arctic Basin from the two oceans through choke points like the Bering Strait, as well as characterizing how much comes from rivers. Arctic GEOTRACES is also studying what regulates the Arctic shelf to deep basin exchange, and the role of sea ice in the transport of trace elements and isotopes. (Follow the expedition here.)

The position of the research vessel Coast Guard cutter Healy on August 24, 2015.

The position of the research vessel Coast Guard cutter Healy on Aug. 24, 2015.

The oval shaped blue area in the map above is the basin of the Arctic Ocean, ranging from ~3,500 meters to ~5,000 meters at its deepest. The Healy is currently over a ridgeline named the Mendeleev Ridge, after a Russian chemist and inventor, Dmitri Mendeleev, long dead when the ridge was first discovered by fellow Soviets in 1948. Mendeleev Ridge is about 1,000 meters shallower than the deep Arctic, bottoming out at ~2,500 meters in depth. The Russians maintain that the ridge, with its long reach into the Arctic basin, gives them claim to large sections of the ocean stretching out to the North Pole. The claim remains unresolved, in part because there are so many questions that still remain about the Arctic. As we move into the basin, we will be sampling to try and better constrain what happens at the shelf/basin interface.

polar bear text

All hands on deck alert – huge polar bear 100 yards ahead! Photo: Tim Kenna

When we venture into the Arctic for research, for most of us there is the lingering hope that a polar bear will appear on our watch; at least as long as we are safely outside of its reach. Several polar bear have been spotted by the watchful eyes of the crew as we have moved into the more tightly packed heavy ice away from the marginal ice zone. However, today a very large bear (yes the alert text says “huge”!) was spotted, and it seemed to have us under thoughtful consideration. The following is a string of images that relay the majesty of this incredible creature in its natural environment, moving with great agility over the sea ice.

 Tim Kenna

Polar bear taking a drink and assessing the ship full of researchers. Photo: Tim Kenna

Polar Bear (photo credit Tim Kenna)

Polar bear carefully testing the thinning stretch of sea ice.  Photo: Tim Kenna

Polar Bear (photo credit Tim Kenna)

The polar bear coloring matches easily to the Arctic ice surroundings. Photo: Tim Kenna

Polar bear live only in the Arctic and rely almost entirely on the marine sea ice environment for their survival. They use the ice in every part of their daily life, for travel, for hunting ringed seal, their favorite food, for breeding and in some cases for locating a birthing den. Their wide paws, which you might be able to see in these photos, distribute their weight when they walk on the sea ice, which late in the season can be quite thin in the annual ice region, melting down to only a thin crust over the water. Their large size, clearly visible in these photos, belies the fact that they are excellent swimmers, helped by their hollow fur, which traps air to keep them buoyant, as well as the stiff hair and webbing on their feet. For all their cuddly appearance, they are strong hunters. Currently polar bear range in conservation status from Vulnerable internationally, to Threatened in the U.S., primarily the result of a warming climate that is melting their habitat…sea ice.

Polar Bear moving easily across the ice. (photo credit Tim Kenna)

Polar bear move easily across the ice, even though males can weigh up to 1,500 lbs. Photo: Tim Kenna

Polar bear

Polar bear use their natural agility to avoid the thinner sections of sea ice. Photo: Tim Kenna

Polar Bear takes measure of the Healy. (Photo credit Tim Kenna)

Polar bear takes measure of the Healy. Photo: Tim Kenna

Polar bear taking a moment to drink. (Photo credit Tim Kenna)

Polar bear taking a moment to drink from an open lead in the Arctic. Photo: Tim Kenna

Arctic Sea Ice Extent

Daily Arctic sea ice extent Aug. 23, 2015. Source: National Sea Ice Data Center

The Arctic is approaching the annual low for sea ice extent, which occurs each year in September. An image of sea ice extent for today (shown in white) against an average of the last thirty years (outlines in yellow) shows how our annual sea ice cover has dropped. Today’s cover is 2.24 million square miles (5.79 million square kms), which is  521,200 sq. miles (1.35 million square kms) below the last 30 year average period. Aside from being of concern to the polar bear, this is part of why Arctic GEOTRACES is so important. We need to understand the role of sea ice in current circulation patterns and delivery of trace elements and isotopes in the Arctic, and then bring this more complete understanding forward to our careful examination of the changing Arctic.

Tim Kenna captures himself in the field surrounded by Arctic sea ice. (photo credit Tim Kenna)

Tim Kenna captures himself in the field surrounded by Arctic sea ice.

Margie Turrin is blogging for Tim Kenna, who is reporting from the field as part of the Arctic GEOTRACES, a National Science Foundation-funded project.

For more on the GEOTRACES program, visit the website here.

First to arrive and last to leave…

Sugar - Sun, 08/23/2015 - 18:17
It is hard to believe that just a few days ago, the hotel had 30+ college students
roaming the hallways and the parking lot was full of SUV’s washed in clay, sand and
mud. When most of the second phase of the SUGAR project had come to a halt, there
was still work to be completed by the Seismic Source Team (SST). In order to
understand why, let me take you through the work schedule of the SST.
Dr. Harder and I drove to Atlanta on July 1st after completion of the ENAM
project in North Carolina and began scouting the shot-holes we would need to drill, load
and stem i.e. fill before the shot dates, which were scheduled for August 7th and 8th for
Line 2 and August 14th for Line 3. When scouting, you want to ensure that the shot-hole
locations selected have good, accessible roads and enough space for the drillers as well as
work crew to move in and out of easily. However beforehand, you want to ensure that
you have the permits to access different properties and have the correct keys for the
property entrance/exit gates, which Donna took care of. Scouting holes took 4 days
before drilling began on July 7th until July 29th.
An example of a good, accessible road for the drillers and SST to use.Pick a lock, any lock. One of the entrance/exit gates to a shot location. Thankfully, we
had the key. I just had to test it on each lock to open the gate. A typical workday would consist of waking up at 6:30 am, eating breakfast at 7
am and leaving to work at 7:30/8 am. We would arrive on site about an hour later and the
drillers would set up and begin drilling. This would take about 2-3 hours at some holes
and 3-4 hours at others. The last hole composed of hard rock took about 14 hours to
complete. That does not include the time it took for us to stem the hole. We would
prepare the charges to load into the hole when the drillers had ~20 ft left to drill. They
drilled up to ~80 ft at the 2 shot-holes on the ends of Line 2 and ~70 ft for the remaining
13 shot-holes. For Line 3, they drilled all 11 holes to ~60 ft. After drilling and loading
the charges into the ground, Dr. Harder would lead the drillers to the next shot-hole while
Galen, Yogi and I would stay behind to stem the hole with gravel, sand and plug it with
bentonite. We would also check the detonators to make sure they worked before heading
off to the next shot-hole to repeat the process. On average, we would drive anywhere
from 100 – 200 miles per day depending on what we were doing and where we needed to
go.
Yogi (Victor Avila, left) and Galen preparing 2  charges to be lowered into the shot-hole.
Each charge contains 2 detonators attached  to 2 boosters indicated by the sets of wires.The drillers lowering the charge into the hole with Yogi carefully holding the detonator (orange wire) chords.
On the left is the water truck and to the right is the drill rig."The Beast" with a 1.1 Explosives placard after transporting the source materials to the shot location.Galen taking a GPS waypoint of the loaded shot-hole while Ashley tests the detonators to ensure that they are working.Dr. Harder (left) and Kent splicing the wires at one of the shot-holes to connect the detonators in order to shoot. The routine changed once drilling was complete. We made our way to Vidalia
where we met with Donna, Dan and everyone at the instruments center and began
preparing our equipment for the nights we were going to shoot. Shots would start at 11
pm and last until as late/early as sunrise depending on the weather conditions as well as if
the detonators would connect. The days that the deployment team members were
flagging and deploying instruments, we were busy driving to shot-holes and cleaning the
ones that blew out. The idea is that you make the shot-hole location look the way it did
before the shot took place.
Shot-hole 7 on Line 3. It looks like a regular hole, but it is actually about 5ft deep and has a 5ft diameter cavity.Using the backhoe to clean up the above shot-hole.After clean up!!I can honestly say there was never a dull moment while working on the SST. I
remember Donna saying at our farewell dinner something along the lines, “We do all this
work for just a disk of data, but it’s all worth it.” She could not have summed it up any
better than that.

Here’s to another successful project….salud!

Ashley Nauer - UTEP

Tracing the Arctic

TRACES of Change in the Arctic - Wed, 08/19/2015 - 00:07
Leaving Dutch Harbor

The U.S. Coast Guard cutter Healy leaving Dutch Harbor, Alaska, and heading to the high Arctic for the GEOTRACES research cruise. It doesn’t take long to move from a landscape of steep carved cliffs to one of endless waves on an Arctic passage. Photo: T. Kenna

Dutch Harbor Alaska is located on that long spit of land that forms the Aleutian Islands of Western Alaska. Research vessels launch from this location and head northeast into the Bering Sea on their way to the Bering Strait, the gateway to the Arctic.

map of Dutch Harbor

Dutch Harbor, Alaska (from http://www.vacationstogo.com)

Our research cruise is part of the international Arctic GEOTRACES program, which this summer has three separate ships in the Arctic Ocean. The Canadian vessel headed north in early July, and the German vessel will follow a week behind the Healy. Each will be following a different transect in the Arctic Ocean to collect samples. The U.S. vessel has 51 scientists on board, each with a specific sampling program. We will focus our time in the western Arctic, entering at the Chukchi Sea. (Follow the expedition here.)

What is GEOTRACES studying? The program goal is to improve our understanding of ocean chemistry through sampling different trace elements in the ocean waters. Trace elements can be an asset or a liability in the marine system, providing either essential nutrients for biologic productivity, or toxic inputs to a rapidly warming system. This part of the larger program is focused on the Arctic Ocean, the smallest and shallowest of the world’s oceans and the most under siege from climate change. Results from this cruise will contribute to our understanding of the processes at work in the Arctic Ocean, providing both a baseline of contaminants for future comparisons as well as insights into what might be in store for our future.

The land surrounding the Arctic Ocean is like a set of cradling arms, holding the ocean and the sea ice in a circular grasp. Within that cradle is a unique mix of waters, including freshwater from melting glacial ice and large rivers, and a salty mix of relatively warm Atlantic water and cooler Pacific water. Our first sample station lasts over 24 hours and focuses on characterizing the chemistry of the water flowing into the Arctic from the Pacific Ocean. This is critical for locking down  the fluxes and totals of numerous elements in the Arctic.

Map of sea ice

Daily map from the ship showing sea ice cover. Yellow is the marginal ice, and the red is heavy ice. The location of the Healy is visible at the lower edge of the photo at the edge of the red dot.

In the past the “embrace” of the Arctic land has served as a barrier, holding in the sea ice, which is an important feature in the Arctic ecosystem. In 2007, however,  winds drove large blocks of sea ice down the Fram Stait and out of Arctic. In recent years the Arctic sea ice has suffered additional decline, focusing new attention on the resource potential of this ocean.

Unexpectedly this year, the sea ice is projected to be thick along the proposed cruise track, thick enough that it might cause the ship to adjust her sampling plan.

Walrus

Walrus resting on Arctic sea ice. Photo: T. Kenna

The walrus in the above image are taking advantage of the Arctic sea ice. Walrus use the ice to haul out of the water, rest and float to new locations for foraging. Walrus food of preference is mollusks, and they need a lot of them to keep themselves satisfied, eating up to 5,000 a day, using the sea ice as a diving platform. As the ship moves further from shore, we will lose their company.

Margie Turrin is blogging for Tim Kenna, who is reporting from the field as part of the Arctic GEOTRACES, a National Science Foundation-funded project.

For more on the GEOTRACES program, visit the website here.

Introducing PAPRICA

Chasing Microbes in Antarctica - Tue, 08/18/2015 - 14:00

I’m very excited to report that our latest paper – Microbial communities can be described by metabolic structure: A general framework and application to a seasonally variable, depth-stratified microbial community from the coastal West Antarctic Peninsula was just published in the journal PLoS one.  The paper builds on two very distinct bodies of work; a growing literature on microbial community structure and function along the climatically sensitive West Antarctic Peninsula, and a family of new techniques to predict community metabolic function from 16S rRNA gene libraries, which we are calling metabolic inference.

The motivation for metabolic inference is in the large amount of time that it takes to manually curate a likely set of functions for even a small collection of 16S rRNA genes.  In today’s world, where most analyses of microbial community structure consist of many thousand of reads representing hundreds of taxa, it is simply impossible to dig through the literature on each strain to see what metabolic role each is likely to be playing.  Ideally a researcher would use metagenomics or metatranscriptomics to get at this information directly, but it is not advisable or desirable in most cases to sequence hundreds of metagenomes or metatranscriptomes (necessary for the kind of temporal or spatial resolution many of us want these days).  Metabolic inference provides a convenient alternative.

A quick Google Scholar survey of the number of studies since 2005 that have used high throughput 16S rRNA gene sequencing.

A quick Google Scholar survey of the number of studies since 2005 that have used high throughput 16S rRNA gene sequencing.  Over the last ten years we’ve collected an astonishing amount of sequence data from a diverse array of environments, however, much of this data has been from taxonomic marker genes like the 16S rRNA gene, leaving microbial community function largely unknown.  PAPRICA and other methods that try to infer microbial functional potential from 16S rRNA gene data can help bridge this gap.

The basic concept behind all metabolic inference techniques (e.g. PICRUSt, tax4fun, PAPRICA) is hidden state prediction (HSP) (you can find a nice paper on HSP here).  In 16S rRNA gene analysis metabolic potential is a hidden state.  The metabolic inference techniques propose different ways to predict this hidden state based on the information available.

Our small contribution to this effort was to develop a method (PAPRICA – PAthway PRediction by phylogenetIC plAcement) that uses phylogenetic placement to conduct the metabolic inference instead of an OTU (operational taxonomic unit) based approach.  Our approach provides a more intuitive connection between the 16S rRNA analysis and the HSP (or at least it does in my mind) and can increase the accuracy of the inference for taxa that have a lot of sequenced genomes.

Most analysis of large 16S rRNA datasets rely on an OTU based approach.  In a typical OTU analysis an investigator aligns 16S rRNA reads, constructs a distance matrix of the alignments, and clusters the reads at some predetermined distance.  By tradition the default distance has become a dissimilarity of 0.03.  This approach has some advantages.  By clustering reads into discrete units it is easy to quantify the presence or absence of different OTUs, and it allows microbial ecologists to avoid problems with defining prokaryotic species (which defy most of the criteria used to define species in more complex organisms).  To conduct a metabolic inference on an OTU based analyses it is possible to simply reconstruct the likely metabolism for a predefined set of OTUs based on the OTU assignments of published genomes.  This works great, but it limits the resolution of the inference to the selected OTU definition (i.e. 0.03).  For some taxa, such as Escherichia coli (and plenty of more interesting environmental bugs), there are many sequenced genomes that have very similar 16S rRNA gene sequences.  PAPRICA provides a way to improve the resolution of the metabolic inference for these taxa.

Our approach was to build a phylogenetic tree of the 16S rRNA genes from each completed genome.  For each internal node on the reference tree we determine a “consensus genome”, defined as all genomes shared by all members of the clade originating from the node, and predict the metabolic pathways present in the consensus and complete genomes using Pathway-Tools.  To conduct the actual analysis we use pplacer to place our query reads on the reference tree and assign the metabolic pathways for each point of placement to the query reads.  One advantage to this approach is that the resolution changes depending on genomes sequence coverage of the reference tree.  For families, genera, and even species for which lots of genomes have been sequenced resolution is high.  For regions of the tree where there are not many sequenced genomes resolution is poor, however, the method will give you the best of what’s available.

Fig_2

Figure from Bowman and Ducklow, 2015.  PAPRICA includes a confidence scoring metric that takes into account the relative plasticity of different genomes.  In this figure each vertical line is a genome (representing a numbered terminal node on our reference tree), with the height and color of the vertical line giving its relative plasticity (which we refer to as the parameter phi).  The genomes identified with Roman numerals are all known to be exceptionally modified, which is a nice validation of the phi parameter.  Many of these are obligate symbionts.  I) Nanoarcheum equitans II) the Mycobacteria III) a butyrate producing bacterium within the Clostridium IV) Candidatus Hodgkinia circadicola V) the Mycoplasma VI) Sulcia muelleri VII) Portiera aleyrodidanum VIII) Buchnera aphidicola, IX) the Oxalobacteraceae.

PAPRICA provides some additional helpful pieces of information.  We built in a confidence scoring metric that takes into account both predicted genomic plasticity and the size of the consensus genome relative to the mean size for the clade (deeper branching clades will have a bigger difference), and predicts the size of the genome and number of 16S rRNA gene copies associated with each 16S rRNA gene, both of which have a strong connection to the ecological role of a bacterium

For our initial application of PAPRICA we selected a previously published 16S rRNA gene sequence dataset from the West Antarctic Peninsula (our primary region of interest).  One thing that we were very interested in looking at was whether we could describe differences between microbial communities organized along ecological gradients (e.g. inshore vs. offshore, or surface vs. deep water) in terms of metabolic structure in place of the more traditional 16S rRNA gene (i.e. taxonomic) structure.  Using PAPRICA to convert the 16S rRNA gene sequences into collections of metabolic pathways we found that we could reconstruct the same inter-sample relationships identified by an analysis of taxonomic structure.  This means that a microbial ecologist can, if they choose, disregard the messy and sometimes uninformative taxonomic structure data and go directly to metabolic structure without losing information.  Applying common multivariate statistical approaches (PCA, MDS, etc.) to metabolic structure data yields information like which pathways are driving the variance between sites, and which are correlated with what environmental parameters.  This information is much more relevant to most research questions than the distribution of different microbial taxa.  It is worth noting that while inter-sample relationships are well preserved in metabolic structure, the absolute distance between samples is much less than for taxonomic structure.  This might have some implications for the functional resilience of microbial communities, which we get into a little bit in the paper.

PAPRICA was an outgrowth of a couple of other papers that I’m working on.  At some point the bioinformatic methods reached a point where separate publication was justified.  As a result, and reflecting the fact that I’m much more an ecologist than a computational biologist, PAPRICA is not nearly as streamlined as PICRUSt (which is even available through an online interface).  I’ve spent quite a bit of time, however, trying to make the scripts user friendly and transportable.  Anyone should be able to get them to work without too much difficulty.  If you decide to give PAPRICA a try and run into an hitches please let me know, either by posting an issue in Github or emailing me directly!  Suggestions for improvement are also welcome.

L2-14

Sugar - Sun, 08/16/2015 - 22:33
... so my mother can see I'm wearing a hardhat (Hi Mom).  Galen getting it done, Natalie with commentary, Yogi counting it down ...



Shot L3-01 video

Sugar - Sun, 08/16/2015 - 21:52


HUGE THANKS to all the volunteers who worked so hard to make this project such a great success. It  was a pleasure working with you and getting to know you all.  Also mega thanks to all the landowners who were kind enough, and trusting enough, to let us put a source on their property.  None of this could have happened without your generosity and spirit of curiosity.  Thanks so much.

Dan



What goes bump in the night? We do.

Sugar - Sun, 08/16/2015 - 11:30
Steve Harder prepares to detonate a shot.Controlled blasts in deep holes are the source of sound waves for our program.  We set them off in the middle of the night because that is when it is quietest along the county and state roads where our instruments are shallowly buried on profiles across eastern Georgia and listening for sound waves.  During the nights of Aug 7, 8 and 11, our blasting experts Steve Harder, Galen Kaip and Ashley Nauer prepped and detonated 25 blasts along our lines, with some help from other enthusiastic scientists (like me).  Our shots have between 200 and 1600 lbs of explosives – mostly ammonium nitrate emulsion. At each shot, we connect a long wire between the drill hole and a blast box, move back a safe distance from the shot site, wait for the appointed time, and set off the blast. The blast box is used to detonate the shot at a very accurate time. There were two shooting teams, and each has different time windows for blasting to ensure that we only do one blast at a time. If two blasts occurred at the same time, the sound waves could interfere with one another.
Ashley Nauer and Kent Anderson wire up a shot.
When the blast goes off, you feel it more than hear it.  The sound waves radiate out from the shot traveling both within the earth and along the surface. Waves that travel along the surface of the earth (“surface waves”) cause the most ground shaking. If the ground is wet, sometimes a geiser briefly occurs 5-10 seconds are the explosion.  Not surprisingly, plenty of people are interested in experiencing this besides us!  Several of the property owners who very kindly gave us permission to set off these blasts on their land came out in the middle of the night to spectate.
Even putting aside the obvious rush of setting off a bunch of blasts, its fun to be out and about in the Georgia country side at night.  A cacophony of sounds echo around the forests from crickets and frogs.  Immediately after a shot, all of these creatures very briefly go silent – they know that something has happened! And then they ramp up again.  We also see other animals prowling around, including amardillos. A meteor shower occurred during our final night of blasting, which we could see quite well from the rural stretches of Georgia, far from light pollution of population centers.

Donna Shillington, LDEO

Jim Gaherty illuminates a steaming hole that formed over the shot site from the blast.
The shot team filled in this hole the next day.Armadillo patrols one of shot sites.

More updates from our field teams...

Sugar - Sun, 08/09/2015 - 12:35

Seventeen teams are rounding up 1953 small seismic stations along our 350-mile-long line across eastern Georgia, and they continue to send texts and pictures with updates on their work…

“21757. Still kickin”
Kevin hunts for missing texans with the metal detector....
“Team 11 is all done and headed home to the mother ship”

“We’re not coming back unless we have all of them!”

“We had a helper at site 20431!”

“Hello Donna Rach and I are crushing it right now”

“Daily check in, we’re making good time so we should see the puppies soon enough”


Making metadata...
“Recovered a Texan at stop 20858. This one doesn’t seem to be working correctly, whenever I press it it just tells me things like “The Cowboys are America’s team” and “Bush was an American hero”. Weird.



“We got to 20170 the one with the ant colony”

Loaded up with Texans and geophones
“Stop 20804. Everything’s fine, except some guy came out of the woods and bit Brent. All he’s saying now is “brains” and is acting super creepy. I’ll keep an eye on it and only use the shovel if necessary”




“Will do! I will let you know if we become stuck… Looks likely”

Unearthing another Texan

“Just beat the downpour and headed for base”

“Stop 20879. Found the Texan disconnected from the geophone on top of where we buried it with pieces of bag around it, looked everywhere for the geophone. Found it about 5 m down the hill near the tree line with bite marks all along it. Either an animal dug it up or a very hungry confused thief”



Picking up litter?
“Found 2 dollars at 21058! Who says geology doesn’t pay well?”

Was not seen on the line...
Was seen on the line... yikes.

Best texts from the field (so far...)

Sugar - Thu, 08/06/2015 - 07:43
Seventeen teams have been out deploying small seismographs and geophones along a 300-mile-long profile across eastern Georgia, and they have been checking in with me regularly by text message. Some highlights from texts and pictures from our groups:



“Team4 is Done! I repeat again, 4 is done! Heading back to the sweet onion city! ☺”

“Still alive”



“Team gruesome twosome on our way back to the hub”

“We are gonna skip installing 21520 because both sides of the streets are well maintained yards and there’s not a great place to put a Texan”

“We’re done! Just kidding haha. We’re on our second!”

“We’re in the zone”

“All geophones buried --- I am beat. Where’s a can of spinach when ya need one, lol”

“It's a long way to the top if you want to study rocks”
"Sunrise at station 21779"
“We’re dirty but doing well!”


“Still digging. Still have not reached China. Will attempt again on next hole”


“On 20186 and we lost our bubble level. We even dug up the last geophone to see if I accidentally buried it”

“We just deployed our last station, 20224. Can we go to Jekyll Island?”



Donna Shillington, LDEO

Digging Holes and Filling Batteries -- A party in Vidalia, Georgia

Sugar - Tue, 08/04/2015 - 07:52

The SUGAR deployment team arrived en-masse on Saturday bringing the Line 2 personnel total to a whopping 45! The day started off with science and overview lectures by the SUGAR principle investigators Donna Shillington and Dan Lizarralde.  Students diligently rearranged the ten’s of Texan boxes into a makeshift lecture hall, complete with a projector and a Bluetooth sound system. 

With the science lecture complete and stomachs full of pizza, the entire group ventured out to conduct a practice deployment under the watchful eyes of the PASSCAL instrument team.  All 17 teams participated in the activity, standing in a single file line in front of our hotel digging practice holes, connecting the Texans to the geophones, and mindfully orientating them with their handy-dandy bubble levels. 

After a sweat filled hour under the Georgia sun, we caravanned back to the instrument center for a “battery party”. I call it a battery party in honor of the “streamer parties” that students will often participate in on active source seismic research cruises in which kilometers of cable need to be reeled off and rearranged.  In our case a battery party consisted of the 32 students placing 2 D-cell batteries inside each of the 2,000 Texans.  The instrument center quickly transformed from an orderly lecture hall into a mass of empty battery boxes and disassembled Texans though despite the apparent chaos, we got the job complete and the Texans filled in only a few short hours. 

Next up will be flagging the instrument locations and the actual deployment.  We have our fingers and toes crossed for dry weather and safe road conditions as the student teams prepare to set off on their flagging and deployment expeditions. 

Natalie Accardo - Columbia University, LDEO


The SUGAR2 deployment team hails from all across the United States
covering more than 15 states and 21 different universities/institutions.   

The deployment team sits with rapt attention listening to
the science and overview lecture.

Students practice digging holes and deploying Texans
near our hotel in Vidalia, Georgia.
Students and PASSCAL personnel take over the instrument center
filling 2,000 Texans with D-cell batteries.
The "battery party" comes to an end as the last Texans are filled and
the boxes are rearranged for easy late-night programming by the PASSCAL team.  



2000 “Texans” with all the fixin’s….

Sugar - Sun, 08/02/2015 - 09:21
During our project, we plan to record sound waves generated by a series of controlled blasts on two profiles, one with 2000 instruments (“Texans”) deployed along a 350-mile-long profile across Georgia and another with 700 Texans deployed along an 80-mile-long profile.  In total, that’s 2000 instruments and 2700 deployments!! Lot of instruments means lots of stuff.   The basic components of the instruments themselves were shipped in ~160 big plastic boxes arranged into ~18 pallets.  Each of these instruments will be powered by two D-cell batteries. To power the instruments for both lines, we needed 5500 D-cell batteries.  We picked them up from the Lowes in Vidalia as a 2000-lb pallet.  For each station, we also need flags to mark the locations, and bags and tape to protect the data recorder.  We very quickly filled up our 1800-square-foot field center in Lyons, GA with all these goodies…

Donna Shillington,  LDEO

Freshly delivered pallets of boxes holding all the science equipment
The PASSCAL team re-arranged the boxes into a T for their own devious reasons :)The trusty Silverado loaded down with 2000 pounds of batteries! (Dan for scale).



Drill, Baby Drill! Drilling and filling for the SUGAR seismic shots

Sugar - Fri, 07/31/2015 - 12:14
We are using sound waves to image the subsurface of Georgia along two long transects.  It is like creating a huge x-ray of the geology in the region. Thousands of instruments (termed “Texans”) will record sound waves that are generated from a series of controlled seismic sources (“shots”) that we will set off along the line. 

For the last few weeks, the seismic source team, based at the University of Texas – El Paso, and the drillers have been hard at work drilling twenty-six 60- to 100-foot-deep holes that will contain the explosives used to create the sound waves.  Once the holes are drilled (the first stage of which is termed spudding), emulsion explosives with boosters and caps are carefully installed in the base of the hole and the remaining height is filled in with dirt and gravel (“stemming”). 

Now with the 26 shots drilled and patiently waiting for the electronic signal to blow, all we have left to do is deploy the 2,000 instruments that will record the sound waves … An easy feat for the 50+ scientists, students, and engineers descending on Vidalia, GA over the next few days.  Stay tuned for our progress and adventures as we continue on this epic scientific undertaking.

Natalie Accardo - LDEO

The SUGAR seismic source and science team from left to right:
Steve Harder, Dan Lizarralde, Ashley Nauer, and Galen Kaip
The drill rig set up and drilling a shot on SUGAR Line 2.

Galen Kaip prepares the source charges (white tubes) on the truck bed as
the drillers complete a shot hole.
The source team carefully lowers the prepared seismic charges into the complete shot hole.
Ashley Nauer (red hat) stands waiting with shovel in hand to fill the remaining height of
the hole with sand and gravel.   
The drill team monitors the process of spudding, the very first stage of drilling the
shot hole, for SUGAR line 2.
The source team and drill team push on late into the night to ensure the completion of the
final shot for the entire SUGAR experiment.  

Ramping up for bigger, badder SUGAR Part 2

Sugar - Tue, 07/28/2015 - 23:11
We are in Georgia gearing up for the second phase of field work for the SUGAR project, which will involve collecting seismic refraction data along two profiles spanning eastern Georgia. In the coming weeks, we’ll deploy thousands of small seismometers along county and state roads across the region, which will record sound waves generated by a series of controlled blasts. We can use the sound waves to make pictures of geology beneath the surface. Geological structures beneath Georgia record the most profound events involved in the formation and evolution of the eastern North America continent. In particular, we want to image an ancient suture between Africa and North America that formed when these continents collided to create the supercontinent Pangea, frozen magma bodies from one of the biggest volcanic outpourings in Earth’s history, and continental stretching and thinning that lead to the breakup of Pangea and formation of the Atlantic Ocean.


Map of SUGAR lines, showing two possible locations of the ancient suture (red dotted lines)

We collected similar data in western Georgia last year during the first phase of the SUGAR experiment imaging these same features. During that field program, we deployed 1200 seismometers and set off 11 controlled blasts along a 250-mile-long line, which felt like a big project at the time. But this year, we will go even bigger! In eastern Georgia, we need to span an even larger area to encompass our geological targets. One of the reasons that we need to look at a bigger swath of the earth is that there is a debate about the location of the suture here – it could be as far north as Milledgeville, GA or as far south as Baxley, GA. (In case you are not up on your Georgia geography, those towns are ~100 miles apart). This means longer profiles, more instruments and more blasts! We will deploy a total of 2700 seismometers and detonate 26 blasts along two profiles. The longer profile spans 350 miles from Winder, GA to the Florida-Georgia state line near St Mary’s Georgia. Stay tuned!

Donna Shillington, LDEO 



Stay Tuned for SUGAR 2!!

Sugar - Wed, 07/22/2015 - 21:57
In just a few short weeks a mass of students and scientists will descend on southern Georgia with work boots and sunscreen in hand to take part in the second portion of the SUGAR active source experiment.  Make sure to stay tuned for regular updates on our progress and to learn more about the exciting science that motivates this amazing field expedition!

Tiny Architects

Geopoetry - Fri, 07/10/2015 - 11:00
 Kelly Strzepek.

Foraminifera are tiny plankton that typically build elaborate shells of calcium carbonate. Their kind have lived in the ocean for millions of years. Photo: Kelly Strzepek.

 

Heaved upwards from your deep and watery grave,

From the quiet murk onto a chaotic, brine-encrusted ship deck,

You’re ever so carefully washed free from the mud,

From all the rinsings of continents that settled out of the sea with you

Like snow, softly entombing your remains.

Now through my looking glass, you lie scattered

Like discarded Christmas ornaments,

Lying in broken glory, shards of a former world;

Tiny fossils, utterly bewitching.

Some people say there must be a knowing architect behind all this design;

Looking at your tiny turrets, buttresses, embellishments,

I understand the sentiment.

How is it, and why is it, that you craft such castles

Smaller than a grain of sand?

I know it is your work, not that of some artful watchmaker;

I’ve watched your live descendants raise their miniscule arches,

Lay down their mortar and stone, precisely and perfectly.

Still, it’s hard to believe my eyes. I am desperate to ask you,

Clever protist with no brain, to tell me all your secrets.

I wonder if some life-form, eons hence,

Will ever find my ancient bones,

Marvel at their beauty,

And imagine the life of the mysterious being that grew them.

 

_________________________________________________________________

This is one in a series of posts by Katherine Allen, a researcher in geochemistry and paleoclimate at the Lamont-Doherty Earth Observatory and the Department of Marine and Coastal Sciences at Rutgers University.

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