Search Results (2)

Cosmogenic beryllium-10 and beryllium-7, and the ratio of the two (10Be/7Be), are powerful atmospheric tracers of stratosphere–troposphere exchange (STE) processes; however, measurements are sparse for altitudes well above the tropopause. We present a novel high-altitude balloon campaign aimed to measure these isotopes in the mid-stratosphere called Beryllium Isotopes for Resolving Dynamics in the Stratosphere (BIRDIES). BIRDIES targeted gravity waves produced by tropopause-overshooting convection to study their propagation and impact on STE dynamics, including the production of turbulence in the stratosphere. Two custom-designed payloads called FiSH and GASP were flown at altitudes approaching 30 km to measure in situ turbulence and beryllium isotopes (on aerosols), respectively. These were flown on nine high-altitude balloon flights over Kansas, USA, in summer 2022. The atmospheric samples were augmented with a ground-based rainfall collection targeting isotopic signatures of deep convection overshooting. Our GASP samples yielded mostly negligible amounts of both 10Be and 7Be collected in the mid-stratosphere but led to design improvements to increase aerosol capture in low-pressure environments. Observations from FiSH and the precipitation collection were more fruitful. FiSH showed the presence of turbulent velocity, temperature, and acoustic fluctuations in the stratosphere, including length scales in the infra-sonic range and inertial subrange that indicated times of elevated turbulence. The precipitation collection, and subsequent statistical analysis, showed that large spatial datasets of 10Be/7Be can be measured in individual rainfall events with minimum terrestrial contamination. While the spatial patterns in rainfall suggested some evidence for overshooting convection, inter-event temporal variability was clearly observed and predicted with good agreement using the 3D chemical transport model GEOS-CHEM. Full article

Information about groundwater residence times is essential for sustainable groundwater management. Naturally occurring radionuclides are suitable tools for related investigations. While the applicability of several long-lived radionuclides has been demonstrated for the investigation of long residence times (i.e., years, decades, centuries and more), studies that focus on sub-yearly residence times are only scarcely discussed in the literature. This shortage is mainly due to the rather small number of radionuclides that are generally suitable for the purpose and show at the same time adequately short half-lives. A promising innovative approach in this regard applies cosmogenic radiosulfur (³⁵S). ³⁵S is continuously produced in the stratosphere from where it is conveyed to the troposphere or lower atmosphere and finally transferred with the rain to the groundwater. As soon as the meteoric water enters the subsurface, its ³⁵S activity decreases with an 87.4 day half-life, making ³⁵S a suitable time tracer for investigating sub-yearly groundwater ages. However, since precipitation shows a varying ³⁵S activity during the year, setting up a reliable ³⁵S input function is required for sound data evaluation. That calls for (i) an investigation of the long-term variation of the ³⁵S activity in the rain, (ii) the identification of the associated drivers and (iii) an approach for setting up a ³⁵S input function based on easily attainable proxies. The paper discusses ³⁵S activities in the rain recorded over a 12-month period, identifies natural and anthropogenic influences, and suggests an approach for setting up a ³⁵S input function applying ⁷Be as a proxy. Full article