When Oceans Leak

 

Posted By: Sidney Hemming on March 25, 2016

 Tim Fulton/IODP

Expedition 361’s scientists aboard the JOIDES Resolution, near the end of a successful two-month expedition. Photo: Tim Fulton/IODP

Read Sidney Hemming’s first post to learn more about the goals of her two-month research cruise off southern Africa and its focus on the Agulhas Current and collecting climate records for the past 5 million years.

We reached our last site yesterday morning, off Cape Town, South Africa, and the first core was on deck at 11:15 a.m. It was pretty stiff at the bottom, and its microfossils indicated it was more than 250,000 years at 1 meter. We decided to start again, and ended up with 6 meters in the first core of the B hole, with further indications of a very low sediment accumulation rate of approximately 1.5 cm per thousand years. The next few cores gave us troubles with shattered liners and low recovery, so Ian and I went back to the data from the alternative sites to consider moving. Luckily we decided not to, because things really started looking up.

We just completed the first hole with 300 meters of sediment and a base age of more than 7 million years, and with a quite pleasing accumulation rate below the very top part. We still don’t have quite enough information to evaluate the situation in the upper 1 million years, but it seems very clear that the rest of the site will be excellent. The sediment composition is very similar from top to bottom and very rich in carbonate (so called nannofossil ooze). The gamma ray (measures radioactivity and thus is a sensitive measure of clay) and color measurements give a very nice signal and are varying in concert with each other. The weather has gotten nicer since the beginning of the first hole, and we are hoping the conditions hold and that the sea conditions were the reason for the troubles at the beginning of our first hole. Meanwhile, we have just enough time to complete the triple coring of this site back to 7 million, with maybe enough time for logging of the final hole.

 Jens Gruetzner, Alfred-Wegener-Institut for Polar and Marine Research)

Crew members retrieve the beacon. Photo: Jens Gruetzner, Alfred-Wegener-Institut for Polar and Marine Research

So, the good fortune continues. Each site on this cruise has provided real prize material, and the team members are very eager to get started on the work back at home. We have been burning the midnight oil (or midday, depending on your shift), meeting about the various plans for post-cruise science. There remain a couple of conflicts to resolve, but overall it looks like there will be plenty of great science for each participant, and plenty of opportunities to develop career-long collaborations.

It has been a great privilege to be part of this, and it really makes you realize how powerful these huge efforts, that require the cooperation of so many countries and their scientists, are. It is a very different way of doing science, and not always convenient for the individual, but overall the benefits are huge.

Meanwhile, this is my last post for this cruise. We are less than a week from arriving at our dock in Cape Town, and there is no question that we are all quite eager to get there. The JOIDES Resolution is amazing and the (multiple) staffs of the ship company, catering service, and IODP are truly remarkable. They are friendly, professional and very eager to help us to get the best we can out of this amazing scientific discovery process.

Sidney Hemming is a geochemist and professor of Earth and Environmental Sciences at Lamont-Doherty Earth Observatory. She uses the records in sediments and sedimentary rocks to document aspects of Earth’s history.

 Tim Fulton/IODP

The crew and scientists of Expedition 361. Photo: Tim Fulton/IODP

Posted By: Sidney Hemming on March 19, 2016

 Dick Norris and Jason Coenen. Illustration by Deborah Tangunan

Expedition 361 micropaleontologists with their nannofossil specialties (not quite to scale …): Top, left to right: Margit Simon, Thiago Pereira dos Santos, Luna Brentegani and Deborah Tangunan. Bottom: Dick Norris and Jason Coenen. Illustration by Deborah Tangunan

Read Sidney Hemming’s first post to learn more about the goals of her two-month research cruise off southern Africa and its focus on the Agulhas Current and collecting climate records for the past 5 million years.

Limpopo was awesome! We ended up with close to 4 million years of sediment from our latest coring site, off Mozambique near the Limpopo River. The accumulation rate for the last 2 million years is close to 10 cm per thousand years, so there is potential for highly resolved records in that interval. The accumulation rate between about 2 million and 4 million years is much lower, probably about a quarter, but that is also good news because we only had permission to go 250 meters, and if there had been more sediment we wouldn’t have covered nearly as much time.

The foraminifera are spectacular – translucent, glassy and “very pretty” throughout the whole sedimentary section. We do have a gap or two, as hard as we tried to avoid it, but we have overlap among holes for most of the site, and a continuous record back to close to 2 million years.

During coring at the Zambezi site earlier this week, the micropaleontologists had less to do since there were only two biostratigraphic datums (one foraminifera and one nannofossil), so nannofossil specialist Debs Tangunan made some cute art (above) with each of the biostratigraphers upon a fossil type of his or her specialty. Debs and Luna are the nannofossil specialists; Dick and Thiago are the planktonic (shallow floating) foraminifera specialists; Margit is the benthic (from the bottom) foraminifera specialist; and Jason is the diatom specialist. Jason’s pouting because most of our sites have not been good for diatom biostratigraphy, except the Agulhas Plateau. He has been a great sport though and has been helping with sample preparation and picking benthic foraminifera for a preliminary stable isotope record to help refine the age models for our sampling party.

The Agulhas Current. Image courtesy of Arnold Gordon.

The Agulhas Current. Image courtesy of Arnold Gordon.

We finished up at Limpopo this afternoon and now we are heading south to our final site, which is in the Cape Basin, and only eight hours from the harbor at Cape Town, South Africa. The catering staff put on a fantastic show for the 5-7 p.m. meal – it was sushi!  And what a beautiful layout, with butter carved into the shapes of fish and various melons and other food. It was delicious and amazing!

During the transit to the Cape Basin, which will take a little over four days, we will have a busy time finishing the cores from Limpopo and the Mozambique Channel. We had to put ~1/2 of a hole’s worth of cores to the side to get the shallow sites completed, and we will finish up those cores as we transit to the CAPE site. We must have all the data collected and reports finished before we arrive at CAPE because we are going to have to devote our full attention to the CAPE site in order to get the report finished on that site before we get to port.

CAPE is located right were the eddies that constitute the “leakage” from the Agulhas Current enters the Cape Basin. So this site is going to be very important for tying together the story of how the Agulhas Current system is connected to global ocean circulation. The water depth of CAPE (as well as the other three of our deeper sites from this cruise: Natal Valley, Agulhas Plateau and Mozambique Channel) is in North Atlantic Deep Water (NADW). So we should be able to obtain some great co-registered records of how the shallow and deep ocean circulation are changing through time, as well as how the productivity and temperature and salinity have varied and how these are related in time to southern African climates.

//www.cardiffhalfmarathon.co.uk/">Cardiff Half Marathon</a> to raise money for a charity by running the distance aboard ship. Photo: Tim Fulton/IODP

Stephen Barker (left) and Ian Hall prepare to participate in the March 26 Cardiff Half Marathon. They’ll be raising money for a South African education charity by running the 13.1 miles in laps around the ship’s helideck. Photo: Tim Fulton/IODP

Another exciting thing that is going to happen while we are at CAPE on March 26, is that Co-Chief Scientist Ian Hall and Stratigraphic Correlator Steve Barker, both from Cardiff University, are going to be running a half marathon around the deck of the JOIDES Resolution at the same time the Cardiff Half Marathon is underway in the UK. Steve is a former Lamont postdoc and an adjunct associate research scientist at Lamont.

Their goal is to raise funds for a charity that supports children in South Africa. The small South African charity, located in the Western Cape, is called the Goedgedacht Trust, and it promotes education to help poor rural African children escape grinding poverty.  We are also planning to provide some of the Trust’s children with a tour of the ship during our visit in Cape Town. Ian and Steve will appreciate any support you (or your colleagues) can give!  Donations can be made online. I’m planning to contribute, and I hope you will too.

Sidney Hemming is a geochemist and professor of Earth and Environmental Sciences at Lamont-Doherty Earth Observatory. She uses the records in sediments and sedimentary rocks to document aspects of Earth’s history.

Posted By: Sidney Hemming on March 16, 2016

//joidesresolution.org/">JOIDES Resolution</a>. Photo: Tim Fulton/IODP

Alexis Armstrong and Beth Novak of the International Ocean Discovery Program (IODP) prepare a core for laser engraving aboard the JOIDES Resolution. Photo: Tim Fulton/IODP

Read Sidney Hemming’s first post to learn more about the goals of her two-month research cruise off southern Africa and its focus on the Agulhas Current and collecting climate records for the past 5 million years.

We have finished coring the Zambezi site and are on our way to the Limpopo site. Both are just off shore from major rivers that flow through Mozambique and should provide a record of the terrestrial climate variability in southeastern Africa through time, but we discovered a surprise. Based on short cores from nearby, as well as seismic surveys, we were expecting that the sediment accumulation would be 10 cm per thousand years. We were wrong by almost 10 times. The accumulation rate is approximately 1 meter per thousand years. Luckily, one of the scientists has been studying records from short cores, and the correlations to them is very clear even though the accumulation rates are so much greater, and we have two biostratigraphic datums that are further consistent.

So with our 200 meters of core we were only able to get back to 200,000 years instead of the 2 million years we anticipated. This is happy news on one hand, as this will allow some extraordinarily highly resolved records of climate variability back to approximately 120,000 years, and maybe (with small gaps) back to 200,000 years. But it is also disappointing from the view of the goal to get a long record of climate variability in the Zambezi catchment. It allows different kinds of questions to be pursued, and they are also very valuable. We feared encountering a bunch of sand, and that did not happen, so all in all this was a successful site, and we are still absorbing the change of approach that would be required to get the most out of it.

Expedition 361's coring sites. APT is the Agulhas Plateau. NV is the Natal Valley.

Expedition 361’s coring sites.

We should get to the Limpopo site at about midnight ship time (Cape Town time) tonight, and expect the first core on deck early Thursday morning. It seems highly unlikely that our estimate of sediment accumulation will be much different, but we are eager to find out! The location of our site is on the outside of a terrace feature in the indentation feature on the African margin (both the Zambezi and Limpopo enter the Indian Ocean in distinctive indentations on the eastern margin of southern Africa). Based on the seismic cross sections, the deposit is what is called a “plastered drift,” it is a body of sediment that is built up by bottom currents flowing southward along the margin. So even though the site is in the Limpopo area, its location relative to the currents is such that we may expect to get a similar record here as well. We will need to make some careful comparisons using the many existing short cores to establish how to best apply and interpret our methods.

Meanwhile, things are very busy on the ship. We were not able to complete the measurements and description of the final hole from the highly successful first Mozambique site before arriving here, and we are still working on the Zambezi cores as we approach the Limpopo site. We hope to keep up the pace so we will be finished with both soon. We expect the coring at Limpopo to take approximately two full days. Then we have about four days transit to our final site, CAPE, off the tip of South Africa. We want to have all three site reports completed before we arrive at CAPE since we will have no scrap of extra time after that!

Sidney Hemming is a geochemist and professor of Earth and Environmental Sciences at Lamont-Doherty Earth Observatory. She uses the records in sediments and sedimentary rocks to document aspects of Earth’s history.

Posted By: Sidney Hemming on March 11, 2016

 Tim Fulton/IODP

Scientists crowd around the stratigraphic correlators’ screens as new details come in. Co-chief scientists Sidney Hemming and Ian Hall are on the right, joined by Luna Brentegani, Christopher Charles and Stephen Barker. Photo: Tim Fulton/IODP

Read Sidney Hemming’s first post to learn more about the goals of her two-month research cruise off southern Africa and its focus on the Agulhas Current and collecting climate records for the past 5 million years.

We just completed coring at our northernmost Mozambique site. The sea is still. The weather is hot and muggy, but so still. This is how sediment coring should be. The stratigraphic correlators think they are having a dream. We have no gaps, beyond the absolute minimum from the coring process, and the variability in the physical properties makes correlating among the holes dead easy.  And the variability looks like a fantastic, cyclic climate signal that is continuous back to 7 million years ago!

We are heading to the Zambezi site now. For our two river sites – offshore from the Zambezi and Limpopo Rivers – our big goal is making the most direct connection possible between what happened on land and in the oceans over the past ~2 million years. We’re only expecting about 2 million years because the accumulation rates are higher, but the nice thing about that is that we can get much more detail about the variability.

 Tim Fulton/IODP

The drilling crew works with equipment aboard the JOIDES Resolution. Photo: Tim Fulton/IODP

Among our science party, we have multiple tools to probe how the rainfall may have changed through time. We have organic biomarkers as well as several measures of terrigenous (land-derived) sediment sources, weathering intensity and fluxes. The Zambezi catchment is located at the very southern part of the annual shift in the Intertropical Convergence Zone (the so-called thermal equator), so there is a strong gradient to drier climate to the south.  And that is one of the reasons having both the Zambezi and Limpopo is so exciting to think about. The “great grey-green greasy“ Limpopo catchment is much drier than the Zambezi.

We are going to be so busy. We have finished the coring and yet more than half the cores are waiting to be processed for the various observations and measurements we have been making. We will get to the Zambezi site in less than two days, and the water depth is much shallower there, meaning the cores are going to come up every 20 minutes or so rather than every 45 minutes, as at the northern site. And then we only have about one more day to get to the Limpopo where the same rate of coring is expected.  So we are going to be buried in cores by the time we finish at Limpopo, and we’ll have about four days to finalize the data collection and reports before arriving at our final site, CAPE, off the tip of South Africa. More about CAPE later.

Sidney Hemming is a geochemist and professor of Earth and Environmental Sciences at Lamont-Doherty Earth Observatory. She uses the records in sediments and sedimentary rocks to document aspects of Earth’s history.

Posted By: Sidney Hemming on March 08, 2016

 Tim Fulton, IODP

Sedimentologists Andreas Koutsodendris of University of Heidelberg, Masako Yamane of Japan Agency for Marine-Earth Science and Technology, and Thibaut Caley of University of Bordeaux study freshly split cores aboard the JOIDES Resolution. Photo: Tim Fulton, IODP

Read Sidney Hemming’s first post to learn more about the goals of her two-month research cruise off southern Africa and its focus on the Agulhas Current and collecting climate records for the past 5 million years.

At the time of the previous entry, we were heading toward the waters off Mozambique while hoping government permission would be in hand in time for coring. It was a month after we had left port in Mauritius, and we had a couple of firm deadlines – well, actually one that we later revised due to the delay because of the helicopter evacuation. We decided that if we did not have approval from Mozambique’s Fisheries office by Wednesday, we would give up hope and head to our CAPE site, off the tip of South Africa, with the prospect of another site that was not part of our original plan as a consolation prize.

We did not hear back on Wednesday, so we stopped and brought extra pipe up for the potential extra site. Thursday morning, with no word from Mozambique, we began to head south. Approximately 24 hours later WE GOT PERMISSION! I cannot tell you what an emotional roller coaster this has been for the entire party. Some of us had already started warming up to the alternative site, but everybody is ecstatic that we finally have verbal permission for the Mozambique sites. We hope cores from the Zambezi and Limpopo sites, near major rivers that run through Mozambique, will give us a record of the terrestrial climate variability in southeastern Africa through the last 5 million years that can be compared with the Agulhas Current and other oceanographic factors.

Expedition 361's coring sites.

Expedition 361’s coring sites.

We are approaching our northernmost site, which is a re-occupation of an old Deep Sea Drill Project (DSDP) site 242 on the Davie Ridge in the northern part of the Mozambique Channel. The site, MZC, which will be IODP 1476, in some ways, is more exploratory than the other five of our expedition although there are hints that this will be a good spot for paleoceanography. The original drilling was done in 1972 during the 25th leg of the DSDP – they sailed from Mauritius, too, on the Glomar Challenger, and ended in Durban, South Africa.

As an aside, this reminds me how the DSDP and its descendants – the Ocean Drilling Program, Integrated Ocean Drilling Program, and the current International Ocean Discovery Program (IODP) –  have made an incredible legacy of understanding the evolution of the ocean basins and the evolution of the oceans and climate system through the Cenozoic. We would know far less without these extraordinary programs. The DSDP site 242 was drilled to understand the history of separation between Africa and Madagascar, and to establish a mid-latitude faunal succession (the evolutionary change of marine creatures) for the western Indian Ocean. The hole was drilled and cored intermittently to 676 meters, and the bottom sediment recovered was from the Eocene (~50 million years old). The sediment was nannofossil ooze throughout. Nannofossil ooze is sediment that is made up of mostly calcareous nannofossils, which are single-celled organisms that have a calcium carbonate structure. This is also the composition of the first two sites we cored and a very common composition for tropical and subtropical sites without much terrigenous (land-derived) dust and debris. This location is upstream of the Agulhas Current, and it appears to have an important influence on Natal Pulses (turbulent pulses that are triggered by eddies originating in the Mozambique Channel) that pass down the Natal Valley and lead to the Agulhas Leakage.

 IODP

Barbecue on the JOIDES Resolution‘s “steel beach.” Photo: IODP

We should get to our northernmost site, MCZ/1476, in the early morning on Tuesday March 8. By trimming our program of coring to only include the advanced piston coring and not go to greater depth than needed to capture the 5 million year interval, we think we can still get everything we need at all six sites. It is going to be a really busy final three weeks, but everybody is ready for the challenge.

Meanwhile, the reports are almost finished for site 1475, at the Agulhas Plateau. The correlators were able to put together a splice of cores that provides a continuous section, although there are intervals that will be further scrutinized back home. We had a barbecue on deck Saturday in the nice hot weather, and we are looking forward to the next site.

Sidney Hemming is a geochemist and professor of Earth and Environmental Sciences at Lamont-Doherty Earth Observatory. She uses the records in sediments and sedimentary rocks to document aspects of Earth’s history.

Posted By: Sidney Hemming on February 28, 2016

 Tim Fulton/IODP.

Sedimentologists Thibaut Caley of the University of Bordeaux and Andreas Koutsodendris of the University of Heidelberg and Deborah Tangunan, a paleontologist from the University of Bremen, work in the core lab aboard the JOIDES Resolution. Photo: Tim Fulton/IODP

Read Sidney Hemming’s first post to learn more about the goals of her two-month research cruise off southern Africa and its focus on the Agulhas Current and collecting climate records for the past 5 million years.

A lot has happened since my last post. As we were heading south to the Agulhas Plateau, one of the scientists had to be evacuated by helicopter for medical treatment. We were within a day of the Agulhas Plateau site and had to go back to near Port Elizabeth for the handoff and then return to drill the plateau. The weather at the plateau was bad enough that we were probably going to have a delay anyway, so we didn’t lose too much time. Our colleague is fine now, and our drilling on the Agulhas Plateau has been a success.

We have had some trials and tribulations because of the large ocean swells and because the sediments do not have as strong of a physical property signal as the previous site. Both of these factors increased the challenge for the stratigraphic correlators, so it has been a real cliff-hanger to find out if we can splice together a continuous section. Because of the small signal-to-noise of the physical properties, the scanning took longer and the records for correlating are not quite as clear. This has created a backup in the work flow, and it means the descriptions and scanning (and some sampling) of the split cores will be continuing as we begin our transit. And it means that until all this is completed we will not know for sure how continuous of a record we have. We are reasonably sure we will have few or no gaps in the splice, but it will be nice to see it all completed.

 Tim Fulton/IODP

The end of a fresh core, just brought aboard the JOIDES Resolution. Photo: Tim Fulton/IODP

Meanwhile, we came here thinking that we would get a high accumulation rate record for the last million years, but the accumulation rates are modest between the surface and about 100 meters – approximately 2 cm per thousand years. Below that, they turned out to be really quite nice, approaching 7 cm per thousand years through much of the Pliocene. The low accumulation in the Pleistocene is a disappointment as there is a great interest in the mid-Pleistocene climate transition, but it does look like it is a continuous record. The higher accumulation in the older sediment is exciting because the early Pliocene is a warm time in Earth’s history and the most recent with global temperatures as warm as modern times. So we Earth scientists are quite eager to understand everything we can about this interval. The Agulhas Plateau site, near where the Agulhas Current swings back toward the east, is well situated to provide some important information about linkages of different factors in the climate system.

Again at this site, as with the previous site, the development of the time scale has been fun and exciting to watch. We have four groups of organisms that are aiding in our time scale – in addition to foraminifera and nannofossils, there are abundant diatoms and dinoflagellates here. This is great for the biostratigraphy and also great for our participants whose post cruise research will use diatoms for documenting paleo-environmental changes. The magnetic stratigraphy started out looking bleak because the weak signal was messed up by the coring process in the first hole, due to the ship’s heave in the waves.  They almost gave up, but the second core preserved a great record. So we are going to have an excellent time scale for this site as well.

Expedition 361's coring sites. APT is the Agulhas Plateau. NV is the Natal Valley.

Expedition 361’s coring sites. APT is the Agulhas Plateau. NV is the Natal Valley. Credit: IODP

Meanwhile the saga continues in our quest to get permission from Mozambique to drill in their waters. We have word from our contact in the American embassy that the form has been signed by the Foreign Ministry and is now with the ministry that deals with fisheries. While that process continues, we have to start toward our next site. Our decision is to head toward the Zambezi site, as it is going to take us six days to get there anyway. If we don’t get permission before we arrive, we’ll have to turn around and head for the Cape site.

The Zambezi and Limpopo sites are near major rivers. We hope they will give us a record of the terrestrial climate variability in southeastern Africa through the last 5 million years that can be compared with the Agulhas Current and other oceanographic factors. The hope is that we will get a continuous record with a variety of proxy data for factors such as precipitation, runoff, distribution of vegetation on the landscape, and surface ocean temperatures. The coring is going to be fast at these sites because they are much shallower. In the happy case that we get to drill there, we will then have another long transit to finish off the analyses.

Sidney Hemming is a geochemist and professor of Earth and Environmental Sciences at Lamont-Doherty Earth Observatory. She uses the records in sediments and sedimentary rocks to document aspects of Earth’s history.

Posted By: Sidney Hemming on February 19, 2016

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The team aboard the JOIDES Resolution collected the first four cores of Expedition 361 from the Natal Valley site. Here, scientists prepare to open the first. (Tim Fulton/IODP)

To drill down into the sea floor, the ship uses a large rig and a professional drilling crew. ( Jens Gruetzner, Alfred-Wegener-Institut for Polar and Marine Research)

Professional rig personnel bring the first core aboard. Each segment is 9.5 meters long and is sectioned into smaller pieces for analysis and storage. (Tim Fulton)

Scientists work the core catcher, which holds each segment of core in as it lifted from the sea floor. (Tim Fulton)

Once the cores are split, they are photographed in shipboard imaging equipment called a Section Half Image Logger. (Tim Fulton)

The shipboard labs are ready for scientists to go to work. Kaoru Kubota of the University of Tokyo and Xibin Han of China work on reports in the core lab. (Tim Fulton)

Sedimentologists Julien Crespin of the University of Bordeaux and Alejandra Cartagena-Sierra of Notre Dame take down descriptions of the core. (Tim Fulton)

Nambiyathodi Lathika, a physical properties specialist from India's National Centre for Antarctic and Ocean Research, enters core data at the sample table. (Jens Gruetzner)

Jeroen van der Lubbe of the University of Amsterdam works with a cyrogenic magnetometer to analyze the magnetic properties of a sample. (Jens Gruetzner)

A map of the Agulhas Current, which the scientists of Expedition 361 are studying along with southern Africa's climate history. (Courtesy of Arnold Gordon)

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The team aboard the JOIDES Resolution collected the first four cores of Expedition 361 from the Natal Valley site. Here, scientists prepare to open the first. (Tim Fulton/IODP)

Read Sidney Hemming’s first post to learn more about the goals of her two-month research cruise off southern Africa and its focus on the Agulhas Current and collecting climate records for the past 5 million years.

We finished up at our first core site yesterday, and now we are steaming south toward the Agulhas Plateau. The groups presented their summaries this morning, and the results from this site are awesome.

Inevitably there is a gap between each sediment core because of how the cores have to be taken. The drilling crew drills down to the level of the previous core’s penetration and then sends the piston core down again. There are potential coring artifacts, such as “suck-in” of sediment at the bottom, “fall-in” of sediment at the top (these are descriptive terms), or loss of sediment because the core catcher didn’t catch. That is the reason for triple – and in this case quadruple – holes at each site. The stratigraphic correlators, Steve Barker and Chris Charles, take data from the physical properties measurement tracks and work fast to determine how the cores that are coming up can be correlated to previous cores. They find the gaps and work with the drillers to ensure that the gaps from all the holes do not overlap. With the help of the lithologic description team, they also avoid parts of the core that have been disturbed by the drilling.

At the Natal Valley site, the correlators were able to achieve a continuous splice going back more than 5 million years!  We obtained samples older than that, but they are “floating”. The splice, like it probably sounds, uses the overlapping physical features in the cores to identify a combination of cores that, when pieced together, yield a full continuous record. This splice is where most of the sampling and measurements will be conducted at the post-cruise sampling party. That will probably take place in September to give enough time for the cores to be shipped to Texas A&M and, we hope, scanned with an XRF scanner in order to construct the best sampling plan.

Women scientists and technicians of Expedition 361 on UN Women in Science Day. (Tim Fulton)

Women scientists and technicians aboard the JOIDES Resolution for IODP Expedition 361 on UN Women in Science Day. (Tim Fulton)

We still do not have permission to drill in Mozambique waters. This is causing considerable anxiety for the team, and by steaming south, we will definitely not be able to drill our northern-most planned site. However, if permission comes before we finish the Agulhas Plateau site, we could still meet our Zambezi and Limpopo objectives. The Zambezi and Limpopo are major rivers that drain from the African continent. We hope to capture sediment coming from those two rivers to answer questions about rainfall and runoff and weathering.

The Agulhas Plateau is also an exciting site. It is a little bit north of the sub-tropical front, which is the northern boundary of the Antarctic Circumpolar Current. Today, it is under the Agulhas retroflection, where the Agulhas Current swings back toward the east (see the map at the end of the slideshow). Our goal is to understand how the position of the sub-tropical front and the Agulhas retroflection have changed through the last 5 million years, and how those changes are related to climatic variability in southern Africa.

Allison Franzese’s Ph.D. research used a time-slice approach to compare the modern composition of sediments washed in from the continents with those deposited during the last glaciation about 20,000 years ago (ice at that time covered what today is New York City). She has suggested that the path of the Agulhas retroflection was very similar between modern and glacial times. Her results are enigmatic because they indicate both a weakening of the current and a similar path for the retroflection, and these observations are inconsistent with what is predicted from physical oceanographic modeling. The cores we collect here should allow her to extend her studies back to 5 million years and achieve a much greater understanding of how the system has worked under a range of climate conditions, particularly when combined with results from the Natal Valley site and the Cape site (the final site of the cruise).

As an aside, I am pretty pleased that even though we are sailing through a storm with about 30 knot winds right now and the ship is swaying, I’m still feeling pretty good. Apparently this could change – we are heading toward the “roaring 40s”.

Sidney Hemming is a geochemist and professor of Earth and Environmental Sciences at Lamont-Doherty Earth Observatory. She uses the records in sediments and sedimentary rocks to document aspects of Earth’s history.

Posted By: Sidney Hemming on February 12, 2016

Jeroen van der Lubbe examines the first core brought up by the team aboard the Joides Resolution.

Jeroen van der Lubbe examines the first sediment core of Expedition 361 brought up by the team aboard the JOIDES Resolution. Photo: Sidney Hemming

Read Sidney Hemming’s first post to learn more about the goals of her two-month research cruise off southern Africa and its focus on the Agulhas Current and collecting climate records for the past 5 million years.

We have our first core! The team pulled up 254.1 meters of sediment from the Natal Valley site off southern Africa, near the start of the Agulhas Current. We think we have about 6 million years of history in that core that should be able to tell us details about the how the region’s currents and climate changed through time.

The whole core (IODP 361 U1474A) is actually several cores. Each is 9.5 meters long and is cut into sections that are 1.5 meters for analysis and storage. The top of each of those cores was jostled by the coring process, but we hope we will be able to fill the gaps with cores from the two other holes we plan to drill at the Natal Valley site. It has become standard in the International Ocean Discovery Program’s (IODP) paleoceanography drilling to core three holes, deliberately offsetting the gaps, in order to have a full record from the site. This presents a challenge for our stratigraphic correlators, Steve Barker and Chris Charles, but they are definitely up for it. They spent the time in port and during transit working hard to master the software.  I understand it is powerful, but not easy to work with (a sign on one of their computers says: “exercise extreme patience”).

 Sidney Hemming

Steve Barker’s computer used for correlations comes with a warning: “Caution: exercise extreme patience.” Photo: Sidney Hemming

Seeing our first core come up was very exciting. As it was happening, we were getting age estimates in real time from the paleontologists, and not too much later from the paleomagnetists. The paleomagnetic measurements appear robust, and they show several magnetic reversals, so we can use the known magnetic reversal time scale to help date each part of the core. The foraminifera and calcareous nannofossil species changes in the core catchers (more on this below) are providing a similar estimate of the ages as the paleomagnetics. This is so exciting to watch in real time, I keep thinking about whether there is a way we could reenact this in a classroom setting.

Now we are on the second hole. Hole B is primarily being taken for squeezing out pore waters – this is the water captured in pores of the deep sediment. We hope it can tell us about the salinity and oxygen isotope composition of the water long ago. The oxygen isotope composition of glacial water is important for understanding how much ice there was, as well as the temperature of the deep ocean. Sophie Hines, a graduate student working with Jess Adkins at Caltech, is leading the effort. She and the other four geochemists, including Lamont’s Allison Franzese, are working hard to get the pore waters squeezed. It is a tough operation, and the presses are not always as cooperative as one might wish. The geochemists decorated the most cantankerous press with a photo of Jess, who wrote the proposal for the pore waters project, to ensure they remember whom to blame.

I mentioned the foraminifera and calcareous nannofossils (calcareous means they build their shells with calcium carbonate) that were found in the core catchers. At the bottom of the core barrel – remember Lisa’s analogy to the straw in the milk shake – there is a mechanism that is open when the barrel is going down into the mud. When the core barrel has penetrated into the sediment and the rig starts to pull it up, that mechanism snaps shut, thereby catching the core and keeping it from falling back out, hence the term core catcher. Some of the sediment goes into the core catcher, and it’s a bit messy, so it is taken immediately and used for examining the microfossil content. Sometimes it’s disappointing, but in this case, the microfossils except for the siliceous ones are working out really well. More about the siliceous ones in another post.

Sidney Hemming is a geochemist and professor of Earth and Environmental Sciences at Lamont-Doherty Earth Observatory. She uses the records in sediments and sedimentary rocks to document aspects of Earth’s history.

Posted By: Sidney Hemming on February 08, 2016

Bubba Attryde, a core technician, shows scientists on the <i>Joides Resolution</i> some of the ship's drilling tools. Tim Fulton/IODP

Bubba Attryde, a core technician, shows scientists on the JOIDES Resolution some of the ship’s drilling tools. Tim Fulton/IODP

Read Sidney Hemming’s first post to learn more about the goals of her two-month research cruise off southern Africa and its focus on the Agulhas Current and collecting climate records for the past 5 million years.

Our first day on the ocean was pretty rough. We left the harbor in Mauritius into high winds and choppy seas, and I don’t think I was alone in feeling pretty miserable.  I woke up the next day to calm seas and a much better perspective.

We have been busy with meetings, training sessions, and planning for the core flow, and I think people are getting close to being ready for the 12-hour shifts. My shift is 3 p.m. to 3 a.m., and my co-chief scientist Ian Hall’s is the opposite. It works out pretty well relative to our home clocks (when I start my shift, it’s 8 a.m. back in New York), and we’ll have significant overlap. I plan to get started by noon, and Ian will hang around until 6 or so before going to bed. We have decided we’ll take a break for exercise—should be a good strategy.

The staff is wonderful on the ship. They feed me great meals, and there is even an espresso machine right outside the science office where I sit. Today Kevin Grieger, our operations manager, gave us a tour to the bridge, the drilling rig and the core shack, where we met Bubba Attryde, who has been the core specialist since Glomar Challenger days and continues to make innovations. We went down through the motors and pumps, past the moon pool, and out to the JOIDES Resolution‘s helideck.

The helideck has a special role this cruise. On March 26, Ian Hall and Steve Barker will be running in the IAAF/Cardiff University World Half Marathon Championships. It requires 328 laps around the deck, which is noisy and hot. They are doing it to raise money for a small South African charity called the Goedgedacht Trust, which promotes education to help poor rural African children escape grinding poverty. Ian has learned that the money raised will help bring solar power to schools. When we reach Cape Town, some of the children plan to tour the ship.

It is now official that we will start with the Natal Valley site while we wait for clearance from Mozambique to work on what would have been our first site.

The Natal Valley is at the beginning of the Agulhas Current, where the waters flowing through the Mozambique Channel and the East Madagascar Current come together and flow along the southern Africa coast. A central goal of the expedition is to understand the history of the Agulhas Current and its role in climate variability, and this site could help us characterize how the microorganisms and the land-derived sediments it carries have changed over the last 5 million years.

Recently published evidence from the past 270,000 years from very close to the Natal Valley site also shows that there have been significant changes in rainfall in southern Africa on millennial time scales. We are very interested in getting a longer record of rainfall changes with this expedition. So in effect, we have the dual goals of understanding the nearby climate record from Africa and understanding the ocean currents below which the core is located—both the Agulhas Current and deep water circulation, which currently flows north along the western Natal Valley and is the reason for the sediment “contourite” accumulation that we are coring.

We will be getting to the Natal Valley site about 8 p.m. local time on Tuesday, so we should have cores coming in before daylight on Wednesday. You can feel the excitement start to build. Our staff scientist, Leah, has organized everybody well. The groups gave reports on their methods this morning and will turn in drafts of their methods before we get to the first site. It’s getting close!

Sidney Hemming is a geochemist and professor of Earth and Environmental Sciences atLamont-Doherty Earth Observatory. She uses the records in sediments and sedimentary rocks to document aspects of Earth’s history.

Posted By: Sidney Hemming on February 03, 2016

The scientists aboard the Joides Resolution for Expedition 361

The scientists of Expedition 361, including Co-Chief Scientist Sidney Hemming, will be spending the next two months aboard the Joides Resolution.

Read Sidney Hemming’s first post to learn more about the goals of her two-month research cruise off Southern Africa and its focus on the Agulhas Current and collecting climate records for the past 5 million years.

It’s almost midnight here, and we’ll be setting sail around 7 a.m. The transit will take approximately six days to the first coring site. Right now, we have the uncertainty that we may not have Mozambique clearance in time for the first intended site, so we will have to make a decision when we get to the tip of Madagascar about whether to head toward the proposed first site, or instead go to the site that would be #4, the northernmost site in South African waters. Apparently this is a normal thing that the permissions are not granted until just as the ship leaves (we hope that happens here), and in our case we have rumors that the form has been signed but it is unclear where it is.

So Kevin Grieger, our operations manager, has been calculating times for alternative plans and considering plans we may have to drop if we cannot stick with the original schedule. We may have to skip some of the operations, and we may even have to forgo a site. Our highest priority site is the sixth out of six on our geographic path, so we have to be judicious in our planning in order to ensure we get there. And it is the closest to the port in Cape Town — word is we only have eight hours in the schedule between the coring site and the port — exciting but also scary because of all the work we have to get done before getting into port.

My husband, Gary, and I had fun in Mauritius before we came to meet up with the JOIDES Resolution. Ian Hall (the other co-chief), Leah LeVay (the IODP staff scientist) and I boarded the ship on Jan. 30, and we went into Port Luis for dinner that night to meet up with a few of the scientists, Allison Franzese, Steve Barker (former Lamont post-doc), and Sophie Hines. Sophie is a Caltech graduate student who is leading the pore water sampling program for her advisor Jess Adkins (also a former Lamont post-doc) who was unable to participate in the expedition.

So we have been living on the ship since the 30th and getting ready for the cruise. That involves a lot of meetings and training. Many of the science team did not know each other before we got here, and we also did not know about the others’ research plans. The plans will evolve as we discuss potential overlaps and collaborations. And they will also change as we find out what we really are going to encounter in the cores. We are all getting to know each other and learning what each others’ interests are and trying to come up with a plan that will maximize what we can discover with the materials we will collect on this cruise. It is very different than anything I have done before, and it is exciting. I think it will be a really rewarding experience. The group seems to already have developed a good rapport, and we are all very optimistic.

Before the <i>Joides Resolution</i> leaves port, Lisa Crowder (left) and Rebecca Robinson (right) take students from a girls' school in Mauritius on a tour. Photo: Tim Fulton/IODP

Before the JOIDES Resolution leaves port, Lisa Crowder (left) and Rebecca Robinson (right) take students from a girls’ school in Mauritius on a tour. Photo: Tim Fulton/IODP

While we have been in Mauritius, the BBC picked up on our work, and twitter has been atwitter with blurbs about the cruise and people on the cruise. We have also had quite a few tours through the ship. Dick Norris (from Scripps Institution of Oceanography) and I went to a girls’ school yesterday and discussed global change and encouraged them to think about science. A small group of the girls from that school came for a tour today, and they seemed really keen and engaged. Lisa Crowder, who oversees the ship’s technicians working with core processing protocols and lab equipment, gave a really awesome show that we all enjoyed! She used the straw-in-the-milkshake analogy for coring in the ocean. It was a great visual!

It is supposed to be quite windy tomorrow, so I’m nervous about being seasick and I’m going to take my Dramamine first thing in the morning. I sure hope I am going to get my sea legs quickly!

Sidney Hemming is a geochemist and professor of Earth and Environmental Sciences at Lamont-Doherty Earth Observatory. She uses the records in sediments and sedimentary rocks to document aspects of Earth’s history.

Posted By: Sidney Hemming on January 27, 2016

 Arnold L. Gordon.

The Agulhas Current runs along the southern coast of Africa and is influenced by other flows. Credit: Arnold L. Gordon.

I am on my way to Mauritius to spend a few days with my husband, Gary, before boarding the JOIDES Resolution in Port Louis for a two-month research cruise, IODP Expedition 361, South African Climates. This is my first cruise as co-chief scientist, so I am both excited and nervous. The goal of the cruise is to obtain climate records for the past 5 million years at six sites around southern Africa. Each has its own special focus.

As with research cruises in general, this represents the culmination of a huge effort over many years, in this case led by Rainer Zahn and my co-chief scientist, Ian Hall. Those efforts included planning workshops, site survey cruises, proposal writing and re-writing, and a lot of development of stratigraphic records and proxies of climate-sensitive factors such as temperature and salinity of surface and intermediate waters, positions of the “Agulhas Retroflection,” and evidence for deep ocean circulation.

The cruise is going to an exciting place in the global climate system. Evidence for the vigor of North Atlantic Deep Water overturning circulation (a.k.a. the Great Ocean Conveyor) can be found in the same sediment cores taken from the floor of the southern Cape Basin, off the southwest coast of South Africa, where scientists have found evidence for Agulhas “leakage” of warm, salty water from the Indian Ocean into the Atlantic Ocean.

The Agulhas Current is the strongest western boundary current in the world’s oceans. It flows along the eastern side of southern Africa, and when it reaches the tip of Africa, it is “retroflected” to flow east, parallel to the Antarctic Circumpolar Current. Changes in the Agulhas Current are coincident with climate change in Africa, and thus it may even have been an important factor in the evolution of our species in Africa. Lamont-Doherty Earth Observatory’s Arnold Gordon has made the case that leakage of salt and heat from the Agulhas Current into the Atlantic Ocean is one of the ingredients that enhances North Atlantic Deep Water overturning circulation.

On this cruise, we’re studying the current to collectively try to uncover the story of southern African climates and their connections with global ocean circulation and climate variability for the past 5 million years.

My role is to use the layers of sediment on the ocean floor that either blew in or washed in from land to contribute to understanding of rainfall and runoff, weathering on Africa, and changes in the Agulhas. (I’m working on this in collaboration with fellow sailing scientists Allison Franzese of Lamont, Margit Simon of the University of Bergen, and Ian Hall of Cardiff University, and shore-based scientist Steve Goldstein at Lamont). Questions about rainfall and runoff and weathering will be tackled in sediment cores that are near major rivers. These efforts will also serve to characterize the composition of sediments being carried in the Agulhas Current.

Fortuitously, the sources of sediments along the eastern coast of South Africa have significantly different radiogenic isotopes than those on the western side. Radiogenic isotopes are isotope systems that change due to radioactive decay of a parent isotope and thus respond to the time-aspects of geologic history. We discovered during the Ph.D. thesis of former graduate student Randye Rutberg that in RC11-83, a pretty famous sediment core from the southern Cape Basin, the land-derived sediments have a higher ratio of Strontium-87 to Strontium-86 during warmer climate intervals than during colder intervals, and the values are so high as to require an external source—that is the eastern side of Africa and carried into the Atlantic via the Agulhas leakage.

Franzese did her Ph.D. thesis on land-derived sediment evidence of changes in the Agulhas between glacial times, about 20,000 years ago, and modern times. She documented the map pattern of variability of both the sources and sediment changes, and further confirmed the role of the Agulhas Current in depositing sediments in the South Atlantic. It will be super exciting to extend the observations back to 5 million years and explore how the sources, as well as the Agulhas Current itself, may have changed.

Sidney Hemming is a geochemist and professor of Earth and Environmental Sciences at Lamont-Doherty Earth Observatory. She uses the records in sediments and sedimentary rocks to document aspects of Earth’s history.