Abstract of the project :
A better understanding of past climate variations and their interactions with geosphere and biosphere is essential to apprehend future climatic changes. Most of the available paleoenvironmental proxies were developed and used in oceanic environments. Nevertheless, it is essential to have reliable proxies which can be applied to continental archives, both terrestrial and aquatic. Some specific organic compounds – 3-hydroxy fatty acids (3-OH FAs), produced by Gram-negative bacteria – could be used as such temperature and pH proxies based on recent studies in soils. Nevertheless, these molecules and their source microorganisms have not been studied in detail in lakes yet. It is now essential to obtain accurate information on the
adaptation of 3-OH FA source microorganisms to temperature/pH changes in lakes to potentially developing robust and universal (paleo)environmental proxies.
The main objectives of this work will be to investigate the applicability of 3-OH FAs as new temperature and pH proxies in lakes and to concomitantly compare these new proxies to the existing ones (e.g. GDGTs). To this aim, the source(s) of microbial lipids in lakes will first be assessed. We then envision to develop calibrations between temperature/pH and distribution of
microbial lipids in surface lacustrine sediments previously collected worldwide. Last, these calibrations will be applied to long-term paleoenvironmental reconstructions from two alpine lacustrine cores covering the last 14,000 years.

Quantifying the nature and scale of human-mediated environmental
and land-cover change in the UK over millennia

People have been influencing natural landscapes in the UK for
millennia. These climate-sensitive ecosystems have experienced a
range of land-use pressures including; deforestation, agricultural
development and increasing influx of pollutants. Ecosystems under
pressure become more sensitive to climate-driven disturbance
dynamics such as droughts, flooding, fire and pests. It is predicted
that these climate-induced disturbance events will become more
frequent, increasing the vulnerability of these environments.
Peatlands and forests are important carbon sinks susceptible to
erosion. Ecosystem management is important to regulate these
natural ecosystem services and there is a shift towards
environmental stewardship including upland and river rewilding for
natural flood management, and rewetting of peatlands and
expansion of forests for increased carbon storage.
To further understand ecosystem functioning and potential risk of
landscape change, we need better regional coverage in available
data. Palaeoecology data is available as a past analogue for past
environmental conditions, land-use change and ecosystem recovery.
In particular, Bronze age forest landscapes may provide an analogue
for rewilding upland Britain, but past records remain poorly
resolved. The key challenge for this PhD student is to fill the gaps
and test these hypotheses.
The aim of the project is to quantify local, regional and national
anthropogenic-driven environmental change and land-use history
under varying scales of human-mediated influence.
● Objective 1 - Reconstruct local and regional land-cover
change for upland NW Britain using a multi-proxy
palynological approach
● Objective 2 - Integrate those reconstructions to build a
better spatial and temporal pattern of environmental change
and land-use change across the UK
● Objective 3 - Model environmental and ecological thresholds
to then explore future risk scenarios with each validated
against past observations.
This PhD will incorporate palaeoecological fieldwork, laboratory
analysis, data collection, meta database analysis and modelling. Key
proxies will include pollen analysis (vegetation), charcoal (fire),
geochemistry (flooding), heavy metals and nutrient cycles
(pollutants) across ecological thresholds spanning the Neolithic,
Bronze Age and Iron Age establishment of agriculture and industry.
Other key environmental records may include biological pathogens
and water quality indicators (testate amoebae and diatoms).

This position is funded through the DFG project "Regional reconstruction of water availability to extend instrumental hydroclimatic records into the Late Holocene - a high-resolution investigation of calendar year-dated natural archives from maar lakes in the Newer Volcanic Province, south-eastern Australia". The lacustrine sediment records to be investigated offer ideal conditions for the reconstruction of regional water availability as well as of short-term climate fluctuations during the last millennium. The project work will be carried out at the University of Bremen and in international cooperation with universities in Adelaide (Australia), Bern (Switzerland) and Gdansk (Poland).

Comparative Legacies of Human Land Use in the Brazilian Atlantic Forest

Rapid warming in the Arctic is expected to cause biodiversity change. However, we are lacking basic understanding on how quickly different species adapt and will shift their distribution poleward. This knowledge gap hinders our ability to make precise predictions about the future state of the Arctic. As part of the advertised PhD project three key questions will be addressed: How can we learn from past species specific dispersal pattern inferred from proxy data to better understand and predict future change? How fast can Arctic species shift their distribution northwards to track preferred climate and ecological niches? Which arctic areas should we protect now to safeguard the long-term survival of arctic biodiversity?

The PhD position is part of the PCARB project (Investigating the past climate influence on the carbon accumulation rates of Irish blanket bogs). The research will develop three records of past carbon accumulation rates from coastal, upland and mountain blanket bogs in Ireland. To enhance our understanding of the causes of past carbon accumulation variability, the project will also develop a suite of reconstructions showing past peatland vegetation, surface wetness and peat humification at each site.

A new proxy for ocean circulation and its impact on rapid climate change Project description

The Atlantic meridional overturning circulation (AMOC) plays a fundamental role in transporting heat from the tropics to NW Europe. The finding that AMOC can rapidly weaken, resulting in major cooling in the Northern Hemisphere, remains one of the most fascinating yet enigmatic results in the study of past climates, with critical lessons for our rapidly warming world. The potential impacts of a future shutdown in Atlantic overturning are closely informed by these changes in the past, as recently highlighted in the IPCC’s AR6. However, despite its critical importance, our ability to reconstruct past changes in ocean circulation remains rudimentary.
To advance our understanding of changing ocean circulation and its impact on the carbon cycle and climate, we need new ways of reconstructing past ocean circulation. In this project we will develop a brand-new circulation proxy, based on redox sensitive elements in fossil foraminifera shells, which can vary based on the strength of the circulation. Preliminary data highlight the potential to obtain a remarkably clean and coherent record of change of overturning circulation over rapid millennial climate change events, supporting the use of this novel proxy.

Start of the PhD program at the Université de Montréal is May or September 2023. We are looking for a talented student with interests in ecosystem greenhouse gas balance, soil biogeochemistry, peatland ecology, and Canada’s northern permafrost region.

Climate and environmental impacts of volcanic eruptions in the extratropics

Extremely large volcanic eruptions are among the most violent geologic hazards and sudden climate cooling events on modern Earth, but their impacts on atmosphere, ocean, and environment are barely known. Climate model studies for such large eruptions in the northern and southern extratropics are rare, information that would be crucial for deciphering their atmospheric, oceanic, and environmental impacts in the past.

The PhD Research Fellow will run a state of the art volcano aerosol chemistry-climate model, systematically varying eruption source parameters (i.e., volatiles, altitude, season) for past eruptions in the northern and southern hemisphere extratropics, to constrain the uncertain volcanic forcing and the climate and environmental response. Different initial ocean-sea ice states will be set-up, which are crucial for the model response. The model data will be analysed and compared with available and pilot paleo proxy data and with other available model runs. The climatic impacts will be assessed, both on the atmospheric and oceanic circulation. Funding for field campaigns to the volcanic vents in New Zealand and Japan will be sought, to collect data and to inspect the eruption episode scenarios. National and international collaborators with volcanology and paleo climate proxies (i.e., ice cores, pollen) expertise exist and scientific exchange visits are planned. The PhD Research Fellow will exchange hers/his work at international workshops and conferences and with the VolMIP and PAGES communities.

The PhD Research Fellowship is financed by UiO and will be embedded with existing research groups at MetOs (e.g., VIKINGS, CompSci, Rough Ocean).

PhD #1: Signal preservation in the deepest part of the EPICA Dome C ice core and application to paleoclimate reconstruction from 600 000 to 800 000 years ago

Variations of past climatic and environmental conditions can be retrieved from ice and air bubble composition of ice cores from East Antarctica over the last 800 000 years (EPICA Dome C ice core). A new ice core project should provide records covering the last 1.5 million years (Beyond EPICA ice core). In the deepest part of the ice cores lies the oldest part of the record. The analysis of the deep ice is tricky because the ice layer thinning tremendously affect the temporal resolution: the last 200m of the EPICA Dome C ice core (only 6% of the length of the core) includes 200 000 years of climate record (25% of the age span covered by the core). Moreover, under the influence of (1) elevated temperature, nearly reaching the melting point, and (2) because of the age of the deep ice, diffusion phenomena, extreme growth of the ice crystals, and migration of chemical species within the ice itself can affect the recorded climatic signal.

In the ice itself, preliminary studies showed that the diffusion length can reach several dozens of cm at the bottom of the EPICA Dome C ice core, limiting the interpretation of the water isotope signal. In the gas trapped in the air bubbles (such as O2, N2, CH4 et CO2), diffusive exchange can affect the precision of ice core dating, as well as the reconstruction of pass greenhouse gases concentration. These diffusive effects are still only poorly constrained despite studies of multiple environmental tracers in multiple deep ice cores. One of the main causes is that the resolution at which these cores have been analysed was not high enough to compensate the high levels of thinning the ice underwent. To retrieve a high-quality climatic signal, it is necessary to compensate for both the thinning by increasing the resolution, and for the diffusion by increasing the precision.

PhD #2: Reconstruction of carbon cycle-climate interactions between 600 and 800 thousand years ago from the analysis of the air trapped in the deep ice of the EPICA Dome C Antarctic core.

Many uncertainties remain on the future and past interactions between climate and the carbon cycle, as well as their impact on the different components of the Earth system. In this context, paleoclimatology provides useful information. The Quaternary climate (last 2.58 million years, Ma), is punctuated by warm periods called interglacials, each of them lasting between ~5,000 and ~30,000 years. These interglacials are characterized by reduced ice cover on the Northern Hemisphere continents and alternate with cold periods, called glacials, associated with large ice caps in the Northern Hemisphere. The cyclicity associated with this succession of glacial-interglacial periods changed during the Middle Pleistocene Transition (occurring between ~1.2 Ma and ~700,000 years ago) from ~41,000 to ~100,000 years. Interglacial periods provide relevant information in the context of global warming as they offer a series of natural laboratories to study the processes within the Earth system for a wide range of warm conditions.

Analyses of the ice and the air trapped in the bottom of the EPICA Dome C (EDC) Antarctic ice core could identify several particularly-interesting interglacial periods between 600,000 and 800,000 years ago: Marine Isotope Stage 15 (MIS 15), MIS 17 and MIS 19. MIS 15 and MIS 17 stand out from the climate variations of the last 800,000 years because of the particular pattern of polar warming during these periods, while MIS 19 is the best analogue for understanding the interactions between the carbon cycle and climate change in a context of natural forcings because of its similarity in orbital configuration to the current interglacial. Finally, these 'old' interglacials occur in an intriguing context where glacial-interglacial cyclicity is no longer ~41,000 years but not yet ~100,000 years. However, the study of the 800 000-600 000-year time interval remains globally limited as few Antarctic ice cores record this old period while the analysis of the deep ice in the EDC core that covers this time-interval remains challenging. Thus, we still lack a precise determination of the sequence of events between climate change, carbon cycle variations and orbital forcing during the MIS 15, MIS 17 and MIS 19 interglacial periods and the deglaciations that precede them.