Abstract
Abstract. Combined droughts and heatwaves are among those compound extreme events that induce severe impacts on the terrestrial biosphere and human health. A record breaking hot and dry compound event hit western Russia in summer 2010 (Russian heatwave, RHW). Events of this kind are relevant from a hydrometeorological perspective, but are also interesting from a biospheric point of view because of their impacts on ecosystems, e.g., reductions in the terrestrial carbon storage. Integrating both perspectives might facilitate our knowledge about the RHW. We revisit the RHW from both a biospheric and a hydrometeorological perspective. We apply a recently developed multivariate anomaly detection approach to a set of hydrometeorological variables, and then to multiple biospheric variables relevant to describe the RHW. One main finding is that the extreme event identified in the hydrometeorological variables leads to multidirectional responses in biospheric variables, e.g., positive and negative anomalies in gross primary production (GPP). In particular, the region of reduced summer ecosystem production does not match the area identified as extreme in the hydrometeorological variables. The reason is that forest-dominated ecosystems in the higher latitudes respond with unusually high productivity to the RHW. Furthermore, the RHW was preceded by an anomalously warm spring, which leads annually integrated to a partial compensation of 54 % (36 % in the preceding spring, 18 % in summer) of the reduced GPP in southern agriculturally dominated ecosystems. Our results show that an ecosystem-specific and multivariate perspective on extreme events can reveal multiple facets of extreme events by simultaneously integrating several data streams irrespective of impact direction and the variables' domain. Our study exemplifies the need for robust multivariate analytic approaches to detect extreme events in both hydrometeorological conditions and associated biosphere responses to fully characterize the effects of extremes, including possible compensatory effects in space and time.
Highlights
One consequence of global climate change is that the intensity and frequency of heatwaves will most likely be increasing in the coming decades (Seneviratne et al, 2012)
We identify two multivariate extreme events in the set of hydrometeorological variables in western Russia 2010, based on the spatiotemporal connectivity
As GPP is a key determinant of ecosystem–atmosphere carbon fluxes, we focus on the gross primary productivity (GPP) response to the multivariate hydrometeorological anomaly: we find that the GPP response is entirely positive during the short-lasting hydrometeorological spring event (+17.8 Tg C, Table 1), while it is mainly negative during the summer event (+8.8, −49 Tg C, Table 1)
Summary
One consequence of global climate change is that the intensity and frequency of heatwaves will most likely be increasing in the coming decades (Seneviratne et al, 2012). One well-known example of a compound extreme event is the 2010 western Russian heatwave (RHW). The RHW was one of the most severe heatwaves on record, breaking temper-. M. Flach et al.: Contrasting biosphere responses to extremes ature records of several centuries (Barriopedro et al, 2011). Flach et al.: Contrasting biosphere responses to extremes ature records of several centuries (Barriopedro et al, 2011) It was accompanied by extensive wild and peat fires with smoke plumes about 1.6 km high at the peak of the heatwave in early August, and estimated emissions of around 77 Tg carbon due to multiple fire events (Guo et al, 2017). 55 000 cases of death have been attributed to health impacts of the RHW (Barriopedro et al, 2011)
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