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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 (GPP_ann). GPP_annfrom GOSIF‐GPP in West Siberia (55°–70°N, 50°–90°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°N, 90–130°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 GPP_annto 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. 

Abstract Despite the importance of high-latitude surface energy budgets (SEBs) for land-climate interactions in the rapidly changing Arctic, uncertainties in their prediction persist. Here, we harmonize SEB observations across a network of vegetated and glaciated sites at circumpolar scale (1994–2021). Our variance-partitioning analysis identifies vegetation type as an important predictor for SEB-components during Arctic summer (June-August), compared to other SEB-drivers including climate, latitude and permafrost characteristics. Differences among vegetation types can be of similar magnitude as between vegetation and glacier surfaces and are especially high for summer sensible and latent heat fluxes. The timing of SEB-flux summer-regimes (when daily mean values exceed 0 Wm −2 ) relative to snow-free and -onset dates varies substantially depending on vegetation type, implying vegetation controls on snow-cover and SEB-flux seasonality. Our results indicate complex shifts in surface energy fluxes with land-cover transitions and a lengthening summer season, and highlight the potential for improving future Earth system models via a refined representation of Arctic vegetation types.