Research project MOCCHA – ARCTIC OCEAN 2018 The Role of Marine Biopolymers in Cloud Formation in the High Arctic
MOCCHA (Microbiology-Ocean-Cloud-Coupling – in the High Arctic) – ARCTIC OCEAN 2018 was an international and interdisciplinary research expedition to the central Arctic Ocean during the summer of 2018.
What are the consequences of the dramatic summer sea-ice loss for the Arctic climate? Will the ice continue to disappear at an increasing rate as the exposed ocean surface absorbs increasing amounts of solar radiation? Or might conditions become progressively more favourable for biological activity and associated cloud formation, decreasing the amount of solar radiation received at the surface, possibly counteracting the ice melt? These are vital questions that the MOCCHA 2018 campaign will strive to answer.
More specifically, we will remediate the largest deficiencies in previous studies north of 80°: in which way are biological processes in the open water between the ice floes (leads) linked to the overlying mixed-phase clouds that are known controllers of Arctic climate and the melting and freezing of sea ice. We will also explore the role of biomolecules in stabilizing the mixed-phase clouds, consisting of a mixture of supercooled water and ice, that surprisingly persist for days.
Project description
To address these questions, we conducted unique measurements during a research cruise to the high Arctic in summer 2018 aboard the Swedish icebreaker (I/B) Oden. During the cruise, which took place throughout the most active biologically period and into the autumn freeze-up (early August to September), I/B Oden drifted passively whilst moored to an ice floe. This approach allowed us to utilise a number of innovative techniques and novel measurement approaches with contributions from a team of world-leading scientists from across the natural sciences.
The project should also be viewed as a necessary initiative to ensure continuity of our sparse archives of Artic in situ data. Further, this initiative is a direct continuation and development of outstanding research carried out in a series of unique international icebreaker expeditions to the high Arctic in the years of 1980, 1991, 1996, 2001, 2008, 2014 and 2016. AO2018
The MOCCHA 2018 research cruise aboard I/B Oden resulted in a remarkable and unique collection of atmospheric, sea ice, and ocean data, including biological, chemical, and physical parameters. Sampling over the pack ice is difficult; cold and constantly changing meteorological conditions constitute a continuous challenge. This challenge is compounded when cutting-edge technology is applied to atmospheric, ocean, and sea ice, where organic compounds often are found at deficient concentrations. This often required longer sampling periods for a single sample to be quantitatively analyzed. For the first time, we will use state-of-the-art genomic analysis of ocean-surface, aerosol, and cloud water samples and in situ vertical profiling systems. We will implement novel mass spectrometry techniques to gain insight into how different biomolecules (polysaccharides, monosaccharides, nucleotides, polymeric proteins, peptides, and amino acids) contribute to the formation of clouds. The particulate matter was also captured on grids for further study of morphology and state of mixture with Transition and Scanning microscopy. Further details are available in the reports at the Swedish Polar Research Secretariat's website.
A sampling of cloud and fog water
Since the characterization of the marine biopolymers of cloud water can be used to infer the sources of those aerosols upon which cloud droplets and ice crystals form, the successful deployment of a light-weight string cloud water sampler attached to a large, tethered balloon was an important innovation for the expedition. No balloon-borne active cloud water sampling had previously been performed in the high Arctic region (north of 80°). Fog water was collected onboard the ship with a dedicated cascade impactor. It uses two jet impaction stages, with cut diameters at 6 µm and 40µm.
Sampling of the lead water
The lead surface microlayer was harvested using a miniature boat to examine the dissolved organic matter (DOM) in greater detail. Surface bulk water was collected in narrow depth intervals to ca 50m. Following collection, a sample was first passed through Millipore membrane filters pore size (0.22 µm) under mild vacuum. Secondly, a tangential flow filtration system was used to retentate the high molecular weight DOM fraction (0.22 µm to 5 kDa). To obtain separation into low molecular weight DOM (<5kDa), the sample passed through the system was further filtered.
Moreover, a floating chamber was used to allow us to directly determine the flux of nascent spray particles at the surface of the open leads. The chamber was deployed onto the open lead. It consisted of an enclosure that creates a headspace over the ocean surface from which the spray particle will be measured and collected (more details can be found on the Dept of Environmental Science's (ACES) MOCCHA page.)
Aerosol particles
Using an extensive suite of novel experimental techniques, we experimentally determined aerosol precursor gases, aerosols' microphysical and chemical properties, cloud/fog droplet residuals, and fog/cloud physical and bulk chemical inorganic/organic properties. Gases and aerosol particles were sampled with minimum interference from the ship and from the sea/ice surface surrounding the ship. Aerosol particles and cloud residuals were sampled by specially designed inlets installed on the 4th Deck. The inlets faced in the forward direction to maximize the distance from the sea and the ship’s superstructure. The waste flow of all intakes and instruments was conducted to the pump container located at the port side. A particle filter connected to this plenum was filtering all exhaust air.
To collect sufficient material for above detection limit analyses, cascade impactor samples for aerosol inorganic characterization and the PM1 filter cassette samples for organic analyses had the highest time resolution of all size-resolved chemical samples performed during the expedition. The more detailed size segregated cascade impactors for aerosol organic characterization, and the rest of the filter samplers, all located downstream of the PM10 inlet, required significantly longer sampling times, 24-96 hours. Ambient samples and blanks were carefully handled in a glove box (free from particles and precursor gases) both prior to and after sampling.
Meteorological measurements and vertical profiling
We utilized a suite of remote sensing instruments to make measurements of clouds and an atmospheric vertical structure installed on I/B Oden (link to the ACAS project). In addition to the remote sensing measurements made on board I/B Oden, we measured the different contributions to the surface energy balance over sea ice (heat exchange and momentum) from a mast erected on the floe. Boundary layer in situ profiling was also achieved with a tethered balloon with varying meteorological payloads.
Integrative assessment of Arctic-cloud processes
We will utilize an advanced large-eddy simulation (LES) model that clearly depicts how biology, chemistry, and meteorology interact to replicate the development and progression of an Arctic cloud. The LES model effectively imitates turbulent eddies and cloud formation procedures on a small scale of a few meters. An exceptional aspect of the LES model we developed is that it can sustain ice in mixed-phase clouds without requiring an artificial source of ice crystals.
The observations will be used to define the ability of the aerosol particles to act mixture of supercooled water and/or ice. This will help us study the potential impact of surface and free tropospheric aerosol particle sources on cloud droplet and ice crystal formation over the Arctic pack ice area (north of 80°). The modeled cloud properties (e.g., cloud and ice water content, cloud vertical extent, precipitation) and radiative fluxes will be evaluated against the in situ and remote-sensing observations gathered. After building confidence in the model, it will explore the sensitivity of sea-ice formation and melt to small perturbations in cloud microphysical properties.
Project members
Project managers
Caroline Leck
Professor of Chemical meteorology
Patrica Matrai
Senior Research Scientist Emerita
Members
Annica Ekman
Professor of Meteorology
Emmy Nilsson
Research engineer
Ines Bulatovic
PhD
Joachim Dillner
Research engineer
John Prytherch
Guest Researcher
Jost Heintzenberg
Gästprofessor
Karolina Siegel
PhD
Luisa Ickes
PhD
Michael Tjernström
Professor Emeritus of Boundary layer meteorology
Nils Walberg
Publications
More about this project
Acknowledgement
The Swedish Polar Research Secretariat (SPRS) provided access to the icebreaker Oden and
logistical support. We are grateful to the Chief Scientists Caroline Leck, Patricia Matrai
and Michael Tjernström for planning and coordination of ASCOS 2008 and AO2018, to the SPRS logistical staff and to I/B Oden's Captain Mattias Peterson and his crew.
Link to database
Data from expedition Arctic Ocean, 2018. Dataset version 2. Bolin Centre Database. https://doi.org/10.17043/oden-ao-2018-expedition-2
