The oxygen cycle and a habitable Earth

Abstract

As an important contributor to the habitability of our planet, the oxygen cycle is interconnected with the emergence and evolution of complex life and is also the basis to establish Earth system science. Investigating the global oxygen cycle provides valuable information on the evolution of the Earth system, the habitability of our planet in the geologic past, and the future of human life. Numerous investigations have expanded our knowledge of the oxygen cycle in the fields of geology, geochemistry, geobiology, and atmospheric science. However, these studies were conducted separately, which has led to onesided understandings of this critical scientific issue and an incomplete synthesis of the interactions between the different spheres of the Earth system. This review presents a five-sphere coupled model of the Earth system and clarifies the core position of the oxygen cycle in Earth system science. Based on previous research, this review comprehensively summarizes the evolution of the oxygen cycle in geological time, with a special focus on the Great Oxidation Event (GOE) and the mass extinctions, as well as the possible connections between the oxygen content and biological evolution. The possible links between the oxygen cycle and biodiversity in geologic history have profound implications for exploring the habitability of Earth in history and guiding the future of humanity. Since the Anthropocene, anthropogenic activities have gradually steered the Earth system away from its established trajectory and had a powerful impact on the oxygen cycle. The human-induced disturbance of the global oxygen cycle, if not controlled, could greatly reduce the habitability of our planet.

Breaking the Ecosystem Balance Over the Tibetan Plateau

“…TOP, for example, is a biological process that absorbs energy from sunlight to synthesize oxygen and carbohydrate molecules from carbon dioxide and water. This process seems simple, but it is closely associated with other essential processes in the thermal cycle (e.g., temperature variations), hydrological cycle (e.g., water storage), and biogeochemical cycle (e.g., carbon fixation) (Huang et al., 2021). Therefore, many studies suggested an origin of TOP was close in time to “Great Oxidation Event” and the rise of atmospheric oxygen was directly driven by the evolution of terrestrial ecosystem (Huang et al., 2021; Soo et al., 2017).…”

“…This process seems simple, but it is closely associated with other essential processes in the thermal cycle (e.g., temperature variations), hydrological cycle (e.g., water storage), and biogeochemical cycle (e.g., carbon fixation) (Huang et al., 2021). Therefore, many studies suggested an origin of TOP was close in time to “Great Oxidation Event” and the rise of atmospheric oxygen was directly driven by the evolution of terrestrial ecosystem (Huang et al., 2021; Soo et al., 2017). Based on this, we also analyzed variables related to climatic‐TOP interconnects, plant‐TOP interconnects, soil‐TOP interconnects, and microbial‐TOP interconnects, as well as climatic‐ plant‐ soil‐ and microbial indicator interconnects.…”

Evaluation of the CMIP6 marine subtropical stratocumulus cloud albedo and its controlling factors

“…This indicates that the surface temperature advection may affect cloud albedo in other ways than by affecting the moisture in cloud layers. Furthermore, dust can affect the meteorological environment through radiative effects; consequently, the positive coefficient found in this study may be a reflection of their effects (Sun and Zhao, 2020;Huang et al, 2021). The coefficients of the omega700 were negative for both datasets.…”

“…McCoy et al (2018) have also validated the influence of SS on N d with up-to-date observations. As submicron SS in the MERRA-2 reanalysis data can be simply predicted from wind speed and SST by a parameterization (Jaeglé et al, 2011;McCoy et al, 2018;Li et al, 2018), the effect of SS on the cloud albedo may be dependent on the relationship be-tween the cloud albedo and near-surface wind speed, which may explain the limited effect of SS on the cloud albedo.…”

“Urban Respiration” Revealed by Atmospheric O2 Measurements in an Industrial Metropolis

“…As a necessity for the survival of almost all living organisms on Earth, atmospheric oxygen (O 2 ) is one of the most critical gases in the atmosphere. − However, continuous O 2 observations at ppm resolution are quite sparse since detecting minor O 2 variations against a large natural background is quite challenging . Only a few organizations have conducted long-term atmospheric O 2 measurements, mostly in the natural background.…”