Influence of Indian Summer Monsoon on Deglaciation c.130,000 years ago.

By Katrina Nilsson-Kerr

Understanding of how the monsoon systems of Asia, the East Asian Monsoon and Indian Monsoon, responded to past changes in climate has undergone debate within the palaeoclimate community due to gaps in data at both the temporal and spatial scale (https://www.nature.com/articles/nature18591). Assumptions have been made to infer both of these monsoonal systems to respond similarly to climate forcing. However, a spate of new research has pointed to more complex controls on the past behaviour of the East Asian Monsoon (http://science.sciencemag.org/content/360/6391/877, https://www.nature.com/articles/s41467-018-05814-0) and Indian Monsoon (https://www.nature.com/articles/s41467-018-07076-2 ) systems than previously thought. Our study, published in Nature Geoscience (https://www.nature.com/articles/s41561-019-0319-5), provides further insights into the past behaviour of the Indian Summer Monsoon, its relationship with the East Asian Summer Monsoon and global climate evolution during the penultimate deglaciation (127 to 140 thousand years ago).

Figure: G. ruber used in this study (left hand panel); Joides Resolution – the vessel used in the IODP expedition. Images: P. Anand.

We have exploited International Ocean Drilling Program (IODP) Expedition 353, Site U1446 situated in the northern Bay of Bengal. This location is uniquely situated as it captures surface freshening and increased terrigenous fluxes associated with increased rainfall and fluvial runoff during the summer monsoon season permitting reconstruction of a primary and direct signal of the Indian Summer Monsoon using a range of geochemical proxies. By combining Mg/Ca derived SST’s in planktic foraminifera with their oxygen isotope composition (δ18OC) a proxy for local surface freshening can be extracted; the oxygen isotope composition of the seawater (δ18Osw-IVC). This record of surface freshening is combined with proxies inferred to represent increased terrigenous fluxes to the site during periods of strengthened monsoon; planktic foraminifera Mn/Ca, Nd/Ca and U/Ca are presented in a novel application to reconstruct fluvial runoff.

Our records show that during deglaciation the Indian Summer Monsoon responded to warming in the southern hemisphere while the rest of the northern hemisphere, including the East Asian Summer Monsoon, remained largely in a glacial state. It is inferred that this strengthening of the Indian Summer Monsoon promoted cross-equatorial transport of heat and moisture from the warm, deglacial southern hemisphere into the northern hemisphere. However, full deglacial strengthening of the monsoon occurs following warming in the northern hemisphere. Thus, conveying that the monsoon is an incredibly dynamic system and is not biased to climatic conditions within a specific hemisphere. Ultimately, it is suggested that components of Earth’s internal climate system should not be viewed in isolation; the monsoon and high-latitudes are intrinsically linked.

 

The Present is the Key to the Past

Trace element and isotope proxies in paleoceanography: A synthesis workshop

3 – 5 December 2018, Aix-Marseille, France

geotraces_groupimages_s_little1

Report by Susan Little

At a workshop in December, scientists from 11 countries and 4 continents converged on Chateauneuf de Rouge, Southern France. With expertise spanning modern and paleoceanography, we gathered to talk biology, ocean circulation, particle fluxes, and models of the present and past oceans…

Why focus on the oceans?

In short, the oceans, and the bugs growing in them, are a vital part of Earth’s climate system.

Microscopic algae in the sunlit upper ocean use carbon (from carbon dioxide, CO2) to build their cells. After they die, they sink and decay, a process that ‘pumps’ CO2 from the surface ocean to the deep.

Once in the deep ocean, the CO2 is trapped for hundreds, or even thousands, of years. This process reduces the level of CO2 in the atmosphere, and the resultant greenhouse effect, cooling the planet.

The Present is the Key to the Past?

Charles Lyell famously wrote: ‘The Past is the Key to the Present’. Scientists even use the past to help predict what might happen in the future warming world.

But how do we figure out what happened in the past? The past oceans are long gone, so scientists use proxies to reconstruct particular ocean properties.

Interesting properties might include the availability of nutrients that algae need to grow, or the patterns of ocean currents. Past ocean proxies include a spectrum of all kinds of bio/geo/chemical measurements, made in all sorts of seawater archives, from individual microfossils to ancient sediments collected from the seafloor.

To develop proxies, it turns out that the present is the key

Tuning your Time Machine

A good proxy is a real life Tardis, allowing us to go back in time… But how do we know what, and how well, a proxy is recording an ocean property?

To test and improve a proxy (e.g., Cd/Ca ratios in microfossils as a record of past nutrients) scientists compare modern measurements of the property in seawater (e.g., nutrient concentrations) with the value recorded by the proxy in its modern archive (e.g., in modern microorganisms).

At this workshop, we set out to improve our understanding and application of a range of proxies. We used what we have learned from the modern ocean in the international GEOTRACES program (www.geotraces.org).

The Modern Ocean

Since 2006, GEOTRACES has completed 109 cruises and released two Intermediate Data Products (IDP), in 2014 and in 2017. The IDP2017 includes data from 41 cruises, more than 1866 stations, 470 parameters and 51000 samples

That’s a lot of data! And it’s all freely available to download here: https://www.bodc.ac.uk/geotraces/data/idp2017/

The Wine Work

The workshop addressed the following questions:

State of the Art

What trace element and isotope proxies are currently being measured and modelled in the ocean?

Challenges

Can we use data from GEOTRACES to improve our understanding of proxies for use by the paleaoceanographic (PAGES, www.pastglobalchanges.org) community?

Perspectives

What future technical developments, modelling approaches, cruises or other activities would help to develop or interpret proxy distributions?

It was a fascinating, stimulating, interdisciplinary three days of discussion. Thanks to everyone who was involved[i]. Watch this space for upcoming workshop products!

[i]More details of the workshop:

https://geotracespages.sciencesconf.org/

Thanks to the Sponsors:

PAGES, GEOTRACES, SCOR, US-NSF, Aix-Marseille Université and John Cantle Scientific

 

Meet the committee

The current Geochemistry Group committee are:

Officers

Chair: Dr Christopher Pearce. Senior Research Scientist, National Oceanography Centre, Southampton.

Secretary: Dr Marc-Alban Millet. Lecturer in isotope geochemistry, Cardiff University, Cardiff.

Treasurer: Dr Sam Hammond. Geochemistry project officer, The Open University, Milton Keynes.

Communications: Dr Wesley Fraser. Reader in physical geography, Oxford Brookes University, Oxford.

Ordinary members

Dr Susan Little, Imperial College, London.

Dr Christian März, University of Leeds.

Dr Andrea Burke, University of St. Andrews.

Prof. Craig Storey, University of Portsmouth.

Dr David van Acken, University College, Dublin.

Dr Nicola Potts, University of Edinburgh.

Dr Patricia Clay, University of Manchester.

Co-opted members

Dr Marie-Laure Bagard, University of Cambridge.

Dr Gordon Inglis, University of Bristol.

Post-graduate student representative

Ms. Rachael Shuttleworth, University of Southampton.

 

Goldschmidt 2018, Boston. 

by David van Acken.

The 28th Annual Goldschmidt Conference was held at the Hynes Conference Center in Boston, MA, from August 12th to 17th 2018, assembling around 3500 geochemists from all over the world. With the usual wide spread of topics from the origins of the solar system via biogeochemistry to the management of mining and nuclear waste, this year’s edition had a distinct tilt towards low-temperature geochemistry. Over five days, 16 parallel sessions, plus a joint poster and industry exhibition area allowed for scientific exchange. Plenaries covered topics of exploration of habitable planets, oxygen cycling in coastal waters, inclusivity and diversity, microbial life in planetary interiors and the evolution of Earth’s volatiles. Notably, the poster session on outreach and public education was running on all conference days, highlighting the commitment of the geochemistry community to reach a broader audience than just specialists in the respective fields. Workshops were organized around the conference schedule covering the same wide range of topics presented in the scientific program, and pre- and post-conference field trips allowed for exploration of the geology and marine life of New England.

All-focus

The science presented at the meeting was excellent, with many presentations by students showcasing their projects. Decade-old paradigms such as the Lunar Cataclysm were called into question, showing that the Goldschmidt conference is the prime outlet for new results and hypotheses in geochemistry.

The social events took full advantage of the diversity of the culture and academic landscape of Boston: in addition to the icebreaker and the society receptions, events were held and Fenway Park, home stadium of the Boston Red Sox baseball team, and the Harvard Mineralogical and Geological Museum. The banquet dinner took place in the ballroom of the conference centre.

The conference was a well-organized success, supported by many student helpers and the organization committee. Next year’s edition in Barcelona is eagerly anticipated!

2018 Geochemistry Group Postdoctoral Awards Announced

by Susan H. Little

Winning Geochemists!

For the third year in a row, the Geochemistry Group is thrilled to award two Postdoctoral Prizes, recognizing the outstanding work being carried out by UK-based early career researchers.

We are delighted to announce that the 2018 winners are:

Postdoctoral Medal: Alex J. McCoy-West

ECR Prominent Lecturer: Rosalie Tostevin

ECR Prominent Lecturer

Dr Tostevin is currently a Postdoctoral Research Assistant at the University of Oxford. Her research primarily focuses on the interactions between life and the environment on the early Earth.

She will be offering a choice of two talks on her fully funded (Agilent Technologies) UK-wide tour in 2018-19. Interested institutions are encouraged to contact the Geochemistry Group in the first instance.

The first talk will describe a radical new theory for the genesis of ancient sediments, which transforms our understanding of ocean chemistry and has implications for microbial evolution.

The second lecture will share five years of work tracking the distribution of oxygen in Neoproterozoic basins, and discusses the consequences for early animal life.

Rosalie follows in the footsteps of the successful tours of Dr David Wilson (2017-18) and Dr Kate Kiseeva (2016-17). We can’t wait!

The Geochemistry Group would like to thank Agilent Technologies for generously providing financial support for this award.

Postdoctoral Medal

This year, the Geochemistry Group Postdoctoral Medal was awarded to Dr McCoy-West for the following outstanding paper:

McCoy-West, A.J., Millet, M.A. and Burton, K.W., 2017. The neodymium stable isotope composition of the silicate Earth and chondrites. Earth and Planetary Science Letters, 480, pp.121-132. doi: 10.1016/j.epsl.2017.10.004

This paper presents the first accurate and precise measurement of Nd stable isotope compositions and uses a combination of a double-spike techniques and high-precision TIMS analyses. As such, it marks a significant breakthrough in measuring stable Nd isotopes.

As well as representing a major analytical advance, the paper addresses the problem of the non-chondritic neodymium (Nd) 142Nd/144Nd ratio of the silicate Earth, which has been attributed variously to collisional erosion, nucleosynthetic variations between solar system bodies, or segregation of sulphide to the core.

The data show that chondrites and the silicate Earth possess an indistinguishable Nd stable isotope composition, indicating that Earth’s excess 142Nd is best explained by a higher proportion of s-process Nd in the Earth.

Overall, this is a very impressive paper, both technically and scientifically. Congratulations Alex!

Finally, the Geochemistry Group committee would like to thank all the applicants/nominees for both Postdoctoral Awards. Both were extremely difficult decisions!

Deadline for the next round of applications: 15 January 2019

#GGRiP2018 starts with a Bang, a Pop, and a Dance…

by Wesley T Fraser

J_Rae_start

The Geochemistry Group annual Research in Progress meeting got off to a fantastic start with a sell-out public lecture delivered by Dr James Rae at the Byre Theatre on Monday evening.

James told us all about global climate change, with an explosive introduction to the burning of fossil fuels, a balloon-based demonstration of the influence of water on the thermal capacity of our planet, and a groovy energy dance to explain transfer of solar radiation to the Earth.

J_Rae_danceA thoroughly entertaining evening, with a truly interactive spirit, and informative to boot!

Dr James Rae is a Research Fellow at the University of St. Andrews. His research focuses on understanding past climate change, particular glacial-interglacial cycles, and the climate of the Cenozoic.

You can follow updates from this years conference using the Twitter hashtag #GGRiP2018 and follow James on @mudwaterclimate

ChAOS in the Arctic.

by Christian März

The NERC-funded project “The Changing Arctic Ocean Seafloor” (ChAOS) has been going for a year now, and it is one of the most exciting interdisciplinary projects I have ever been a part of! ChAOS will quantify the effect of changing sea ice cover on organic matter quality, benthic biodiversity, biological transformations of carbon and nutrient pools, and resulting ecosystem function at the Arctic Ocean seafloor. We will achieve this by determining the amount, source, and bioavailability of organic matter and associated nutrients exported to the Arctic seafloor; its consumption, transformation, and cycling through the benthic food chain; and its eventual burial or recycling back into the water column.

We will study these coupled biological and biogeochemical processes by combining

  • a detailed study of representative Arctic shelf sea habitats that intersect the ice edge, with
  • broad-scale in situ validation studies and shipboard experiments,
  • manipulative laboratory experiments that will identify causal relationships and mechanisms,
  • analyses of highly spatially and temporally resolved data obtained by the Canadian, Norwegian and German Arctic programmes to establish generality, and
  • we will integrate new understanding of controls and effects on biodiversity, biogeochemical pathways and nutrient cycles into modelling approaches to explore how changes in Arctic sea ice alter ecosystems at regional scales.

We will focus our research on the Barents Sea, a part of the Arctic Ocean where drastic changes in sea ice cover and water mass distribution are the main environmental control. Common fieldwork campaigns will form the core of our research activity. Our focal region is a N-S transect along 30 degree East in the Barents Sea where ice expansion and retreat are well known and safely accessible. In support of our field campaign, and informed by the analysis of field samples and data obtained by our international partners (in Norway, Canada, USA, Italy, Poland and Germany), we will conduct a range of well-constrained laboratory experiments, exposing incubated natural sediment to environmental conditions that are most likely to vary in response to the changing sea ice cover, and analysing the response of biology and biogeochemistry to these induced changes in present versus future environments (e.g., ocean acidification, warming). We will use existing complementary data sets provided by international project partners to achieve a wider spatial and temporal coverage of different parts of the Arctic Ocean.

The unique combination of expertise (microbiologists, geochemists, ecologists, modellers) and facilities across eight leading UK research institutions will allow us to make new links between the quantity and quality of exported OM as a food source for benthic ecosystems, the response of the biodiversity and ecosystem functioning across the full spectrum of benthic organisms, and the effects on the partitioning of carbon and nutrients between recycled and buried pools. To link the benthic sub-system to the Arctic Ocean as a whole, we will establish close links with complementary projects studying biogeochemical processes in the water column, benthic environment (and their interactions) and across the land-ocean transition. This will provide the combined data sets and process understanding, as well as novel, numerically efficient upscaling tools, required to develop predictive models that allow for a quantitative inclusion seafloor into environmental predictions of the changing Arctic Ocean.

More information can be found at https://www.changing-arctic-ocean.ac.uk/