MAL1b

Atmospheric nuclear weapon testing in the 1950s and 1960s has been worrying, however, in many aspects it was extremely beneficial for environmental sciences. The artificial production of more than 6 x 10²⁸ atoms or about 0.6 tons of radiocarbon (¹⁴C), leading to a doubling of the ¹⁴C/C ratio in tropospheric CO₂ of the Northern Hemisphere, has generated a prominent spike in 1963. This “bomb-spike” has been used as transient tracer in all compartments of the carbon cycle, but also to study atmospheric dynamics, such as inter-hemispheric and stratosphere-troposphere air mass exchange. Moreover, our attempt to accurately determine total bomb produced ¹⁴C led to improved estimates of the atmosphere-ocean gas exchange rate and to a new constraint of the residence time of carbon in the terrestrial biosphere. Today, the transient bomb-radiocarbon signal has levelled off, and the anthropogenic input of radiocarbon-free fossil fuel CO₂ into the atmosphere has become the dominant driver of the ¹⁴C/C ratio in global atmospheric CO₂. The observed decreasing ¹⁴C/C trend in atmospheric CO₂ may thus help scrutinising the total global release of fossil fuel CO₂ into the atmosphere. On the local and regional scale, atmospheric ¹⁴C/C measurements are already routinely conducted to separate fossil fuel from biogenic CO₂ signals and to estimate trends of regional fossil fuel CO₂ emissions. Some prominent examples where the bomb ¹⁴CO₂ disturbance has been successfully used to study dynamic processes in the carbon cycle are discussed as well as our current activities applying this unique isotope tracer for continental scale carbon cycle budgeting.

How to cite: Levin, I.: Radiocarbon in modern carbon cycle research, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4268, https://doi.org/10.5194/egusphere-egu21-4268, 2021.

Research within the field of fluvial biogeomorphology focuses on the impact of organisms, particularly plants, on physical processes and landform development within river environments. This research field has evolved and matured over 50 years such that strong links between plants and river morphodynamics are now established and are increasingly becoming embedded in river management practices.

In this presentation, I provide a personal perspective on the evolution of fluvial biogeomorphology, emphasising five parallel research themes that were initiated in different decades. Research within these themes continues and combines to underpin our current state of knowledge:

The 1970s       Natural vegetation colonises areas according to the degree of river disturbance such that certain plant communities are associated with particular river landforms.

The 1980s       Dead wood pieces influence river morphodynamics and support the development of particular assemblages of physical habitats.

The 1990s       Some large wood sprouts: dead and living trees drive a geomorphological continuum.

The 2000s       River and riparian forest dynamics are linked: field observations, laboratory experiments and numerical models converge.

The 2010s       Many riparian and aquatic plant species can act as river engineers: local engineer species reflect the environmental setting.

2020 onwards    Increasing integration: understanding how interactions between plants and rivers adjust with changes in the biogeographical setting, plant species pool and river energy.

How to cite: Gurnell, A.: Plants and river morphodynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2793, https://doi.org/10.5194/egusphere-egu21-2793, 2021.