ALBERT

Description: The Pan-Eurasian Experiment (PEEX) Science Plan, released in 2015, addressed a need for a holistic system understanding and outlined the most urgent research needs for the rapidly changing Arctic-boreal region. Air quality in China, together with the long-range transport of atmospheric pollutants, was also indicated as one of the most crucial topics of the research agenda. These two geographical regions, the northern Eurasian Arctic-boreal region and China, especially the megacities in China, were identified as a “PEEX region”. It is also important to recognize that the PEEX geographical region is an area where science-based policy actions would have significant impacts on the global climate. This paper summarizes results obtained during the last 5 years in the northern Eurasian region, together with recent observations of the air quality in the urban environments in China, in the context of the PEEX programme. The main regions of interest are the Russian Arctic, northern Eurasian boreal forests (Siberia) and peatlands, and the megacities in China. We frame our analysis against research themes introduced in the PEEX Science Plan in 2015. We summarize recent progress towards an enhanced holistic understanding of the land–atmosphere–ocean systems feedbacks. We conclude that although the scientific knowledge in these regions has increased, the new results are in many cases insufficient, and there are still gaps in our understanding of large-scale climate–Earth surface interactions and feedbacks. This arises from limitations in research infrastructures, especially the lack of coordinated, continuous and comprehensive in situ observations of the study region as well as integrative data analyses, hindering a comprehensive system analysis. The fast-changing environment and ecosystem changes driven by climate change, socio-economic activities like the China Silk Road Initiative, and the global trends like urbanization further complicate such analyses. We recognize new topics with an increasing importance in the near future, especially “the enhancing biological sequestration capacity of greenhouse gases into forests and soils to mitigate climate change” and the “socio-economic development to tackle air quality issues”.

Description: Decadal variations of phytoplankton concentrations in the upstream Kuroshio Extension (KE) region are investigated using outputs from a simple ecosystem model embedded in an eddy-resolving ocean general circulation model, which can well simulate decadal modulations of the KE between stable and unstable states. During the KE stable states, surface phytoplankton concentrations are anomalously suppressed (enhanced) to the south (north) of the KE front. Although the surface phytoplankton concentration anomalies are prominent only during winter to spring as revealed by past studies, it is shown for the first time that significant subsurface anomalies centered around 60 m depth persist even in summer and autumn. Further analyses of nitrogen concentration anomalies suggest that the vertical movement of the isopycnal surfaces, vertical mixing of nutrients, and meridional shifts in the KE jet contribute to the anomalous phytoplankton biomass. Moreover, the remarkable subsurface anomalies in phytoplankton concentration may feedback on to decadal sea surface temperature anomalies by modulating absorption of penetrative shortwave radiation.