The 2020 Heatwave Led to a Larger Enhancement in Annual Gross Primary Production in West Siberia Than in East Siberia

Abstract

Spring and summer vegetation productivity in Siberia shows opposing responses to warmer spring. Spring warming causes excessive vegetation growth and earlier start of photosynthesis, enhancing productivity in spring. However, this leads to reduced productivity in the following season (i.e., summer) through soil moisture depletion. To understand how an exceptional spring heatwave (HW) affected ecosystem carbon uptake, we investigated the spatiotemporal cascade of gross primary production (GPP) and multiple climate variables over Siberia in 2020, using a satellite-retrieved GPP product (GOSIF-GPP) and the ERA5-Land reanalysis data set for 2001-2020. Results showed a positive impact of anomalous spring warming on annual GPP (GPPann). GPPann from GOSIF-GPP in West Siberia (55 degrees-70 degrees N, 50 degrees-90 degrees E) was enhanced by up to 10% above the 2001-2019 average despite continued dry conditions from May to August. In East Siberia (55-70 degrees N, 90-130 degrees E), the GPP increases for May and June were sufficient to compensate for marked reduction of GPP in July due to negative anomaly in radiation. In addition, the higher sensitivity of GPPann to spring temperature in West Siberia than in East Siberia suggests that GPP increase coupled with strong warming and respective excessive vegetation growth might be more pronounced in the western region, as observed in 2020. Our results indicate that the warming trend in spring, combined with possible extreme heat events, could elevate annual carbon uptake in Siberia, particularly in West Siberia. Further, this case study for the extreme HW event that occurred in 2020 can provide useful insight for understanding future change in carbon uptake over Siberia.