Gas group

Instrument-characterisation of a novel low-sample cavity ring down IF laser spectrometer for GHG measurements

Greenhouse gases (GHGs), such as CO2, CH4 and N2O, play an important role in Earth’s climate by absorbing and back-radiating

IPCC, 2023: Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth

Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J.

Romero (eds.)]. IPCC, Geneva, Switzerland, 184 pp., doi: 10.59327/IPCC/AR6-9789291691647.

infrared radiation emitted from Earth’s surface heated by sunlight. The rapid increase in atmospheric GHG concentrations in recent decades is the main driver of current Global warming (IPCC, 2023).
Accurate measurements of paleo-GHG concentration are needed to better understand natural climate variability.
Researchers in the Gas Laboratory of the Physics of Ice, Climate and Earth (PICE) Division at Niels Bohr Institute led by Prof. Thomas Blunier, are working at the forefront of concentration and isotope measurements of a variety of air compounds (e.g. trace gases (CO2, N2O, CH4, …), O2, N2, …) on ancient air extracted from polar ice-cores using state-of-the art measurement techniques such as Isotope Ratio Mass Spectrometry (IRMS) and Cavity Ring-Down Spectroscopy (CRDS). Within the framework of ongoing projects, we acquired a brand new CRDS IF laser spectrometer (ap2e) optimized for simultaneous measurements of CO2, N2O, and CH4 concentrations in air samples. To characterize the performance of the new spectrometer we are looking for a motivated master student with a solid background in physics or related field. The student will work under the supervision of Prof. Thomas Blunier and Dr. Michael Döring. The task of the master project  will be to develop a framework for measurements of gas standards with the new spectrometer to quantify the precision and accuracy of the instrument. In addition, the master student will analyse the measurement data and develop routines for statistical analysis of these data (Allan variance, offset analysis, drift analysis, …) using a scientific programming language such asMatlab or Python. Data analysis will be used to devise measurement strategies for greenhouse gas concentrations in old air from ice cores. The start of the master project will be as soon as possible. If you are interested in becoming part of the “gas lab crew” at PICE and helping us develop novel measurement strategies for greenhouse gas concentrations, or if you have further questions about the project, you can contact us:

Prof. Thomas Blunier: blunier@nbi.ku.dk

Dr. Michael Döring: michael.doring@nbi.ku.dk


CO2 in the ancient atmosphere

From Rubino et al., 2013: (a) CO2 concentration (black circles) and the d13C (brown circles); solid lines are results of the double deconvolution for, respectively, (b) the atmosphere-terrestrial biosphere and (c) the atmosphere-ocean CO2 flux. Error bars are analytical uncertainties and dashed lines show the 1 sigma uncertainty associated to the Kalman filter double deconvolution.

Ice cores contain ancient air and the past atmosphere can be reconstructed from them. However, the past atmospheric composition of CO2 turned out to be a challenge. In the measurements from ice cores uncertainties arise from in situ processes affecting both concentration and isotopic composition. These uncertainties are passed on to calculations on how the past carbon cycle has been affected. The figure from Rubino et al., 2013 shows the status. The only way to minimize the uncertainty is to measure CO2 and δ13C in different ice cores with different impurities. In the frame of collaborative ice core drilling projects in Antarctica, we have access to two new cores. The goal of the 1-year master project is to obtain reliable measurements of both CO2 and δ13C. The focus of the project is the last millennium and interpretation of the records will be in international collaboration.

We have a working system to measure concentration and isotopic composition of CO2 with an Isotope Mass Spectrometer extracted from ancient air trapped in the polar ice sheets. The system has not been used in a while (due to moving the lab) and it needs to be extensively tested and upgraded. The master project is available immediately.

Contact: Thomas Blunier, Tagensvej 16, Office 1.1.11 (blunier@nbi.ku.dk).


Abrupt climate change and the nitrogen cycle

Figure 1: Top δ18O of H2O, a temperature proxy. Bottom N2O concentration [Flückiger et al., 1999].

Nitrous oxide (N2O) is a prominent component of the global nitrogen cycle and an important and strong greenhouse gas in the atmosphere; it is part of a feed-back loop with climate. Most N2O is produced by microbes during nitrification and denitrification in the terrestrial and oceanic realm. The combination of δ18O and δ15N discriminates between oceanic and terrestrial sources while the position dependent 15N in N=N=O distinguishes between nitrification and denitrification sources.

The greenhouse gas N2O has various biological origins distinguishable by their isotopic fingerprint. At times of abrupt climate change, like at the transition from the glacial to the present warm period (Figure 1) nitrous oxide concentrations rise most probably resulting from increased source emissions. We want to investigate which sources are responsible for the change and hope to get insight into how the biosphere is likely to respond to future climate change. This may provide information on whether these gases produce a positive or a negative feedback to the ongoing man-made climate change.

In this 1 year master project the student needs to build an extraction system and connect it to the laser spectrometer. The first step is to measure N2O and isotopomers from atmospheric air samples. The project could involve two students.

Contact: Thomas Blunier, Tagensvej 16, Office 1.1.11 (blunier@nbi.ku.dk).


High resolution greenhouse gas and temperature reconstruction from ice cores

Sketch of the current Copenhagen gas measurement system.

We pioneered methane measurements from a continuous melt stick in 2012 (Stowasser et al.) We are in the process of expanding our pallet of measurements including other trace gases and temperature reconstructions from isotopes in gases. We want to learn what is the exact timing of changes in the greenhouse gases methane and nitrous oxide relative to the temperature changes. The 1 year project involves system development, testing, measurement campaign and interpretation of the climate record.

Contact: Thomas Blunier, Tagensvej 16, Office 1.1.11 (blunier@nbi.ku.dk).

Stowasser, C., C. Buizert, V. Gkinis, J. Chappellaz, S. Schupbach, M. Bigler, X. Fain, P. Sperlich, M. Baumgartner, A. Schilt, and T. Blunier (2012), Continuous measurements of methane mixing ratios from ice cores, Atmospheric Measurement Techniques, 5(5), 999-1013, 10.5194/amt-5-999-2012.


Atmospheric Hydrogen as a new climatic parameter

We know much about the past atmosphere; E.g. the pace at which greenhouse gas concentrations have varied in the past. Our knowledge stems from the air trapped in ice cores. Interwoven with CH4 and CO are production and destruction processes of molecular hydrogen. Hydrogen thus offers complementary information on important components of the chemistry in our atmosphere. To our knowledge neither concentration nor isotope records of molecular hydrogen exist prior to 1993 (2). Our final goal is to extend this record based on ice core measurements. However, several aspects of such an endeavor are unclear. 1) Due to the small molecule size of H2 it is expected that hydrogen is lost after recovery of the ice core. 2) Hydrogen may fractionate during the last step of air occlusion in the ice. Both aspects need clarification.

The master thesis has two aspects 1) Measure the permeability of molecular hydrogen through natural ice. 2) Investigate the potential fractionation during air occlusion in polar firn. For the measurement a system needs to be designed and built.

Our current deep drill project EGRIP (https://eastgrip.org/) offers access to freshly drilled core to investigate above mentioned questions.

Contact: Thomas Blunier, Tagensvej 16, Office 1.1.11 (blunier@nbi.ku.dk).

References
1. Yver CE, et al. (2011) A new estimation of the recent tropospheric molecular hydrogen budget using atmospheric observations and variational inversion. Atmos. Chem. Phys. 11(7):3375-3392.
2. Prinn RG, et al. (2000) A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE. Journal of Geophysical Research: Atmospheres 105(D14):17751-17792.


Modelling the termination of the last Ice Age in Greenland with the Community Firn Model

Are you looking for an exciting Msc thesis project where you can combine your Python computational skills with inverse methods and state of the art datasets of N2 and Ar isotopes in order to look far back in Greenland's past climate? If you are fascinated by polar research and curious about climate change processes this may be a unique chance for you to join a dynamic group with decades of history in polar and ice core research.
You will be looking into the abrupt warming signals during the sudden end of the last Ice Age about 12,000 ago and using a state-of-the-art model of snow densification and gas diffusion you will work towards quantifying the magnitude and rapidity of the abrupt climate change during this time. We require that you are familiar with Python and you can expect your skills to get very sharp during the duration of the project. You will get hands-on experience with polar snow/firn modelling tools and high quality datasets of N2 and Ar isotopes from the air bubbles in the ancient ice. We are a very open and dynamic group with a variety of nationalities and backgrounds as well as a wide international network of collaborations.

Should you have any questions on the project feel free to contact: Vasileios Gkinis and Michael Döring


Recording the sound of ancient bubbles in ice cores

Msc Thesis Project: The sonic signature of ancient air bubbles in ice cores

Keywords: ice cores; paleoclimate; Greenland; polar research; Continuous Flow Analysis; sound measurements; total air content; Python; spectral analysis; bubbles

The air bubbles occluded in polar ice cores contain extremely valuable paleoclimatic information in the form of ancient air, whose composition can be determined in the lab yielding time series of gas concentrations in atmosphere spanning millennia. Another characteristic of the ancient air bubbles is their popping sound emission when ice core samples are being controllably melted for high-resolution Continuous Flow Analysis measurements.
We would like to investigate the audio signal of the “popping” bubbles. Our goal is to perform high quality sound recordings followed by spectral analysis of the bubble popping frequencies in order to infer how many and how large the bubbles are. Therefore, we offer a Master thesis project for a motivated student who will further develop the recording and melting system as well as work on the data analysis of the sounds recordings.
You can expect to gain skills in sound and bubble physics, sound recordings as well as high resolution ice core measurements. You will also work with noise filtering and spectral analysis techniques. Prior experience in data analysis with Python/Matlab is a plus. PICE is an active, multinational/multicultural group with plenty of learning opportunities.

We will be happy to hear from you!
Should you have any questions on the project feel free to contact:
Vasileios Gkinis