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In this study, we apply a three‐dimensional (3D) thermomechanically coupled higher‐order ice flow model to simulate the East Rongbuk Glacier (ERG), Mt. Everest. We first diagnostically investigate its present‐day ice dynamic features in 2009 and then prognostically simulate the glacier during the time period 2010–2100. The ice flow model is initialized based on a Robin‐type inversion method by conducting six sensitivity experiments relating to glacier thermal boundary conditions. We apply two different surface mass balance parameterizations in the model, and both of them can reproduce the observed ice volume loss (around 0.1 km3) during 2010–2020. We find that ERG is likely to experience maximum meltwater runoff at the year 2030 under the SSP‐126 scenario, while under SSP‐370 and ‐585 scenarios, the peak water will both likely occur at around 2060. The ice dynamics may contribute more to ice loss as climate warms in time. Plain Language Summary: The melt of glaciers in High Mountain Asia (HMA) has great impacts on regional water resources and socioeconomy. But it is not an easy task to accurately predict their future changes. The East Rongbuk Glacier (ERG), Mt. Everest, is one of few glaciers in HMA that has relatively rich in situ data for conducting three‐dimensional numerical projections. In this study, we first carefully invert basal frictions at the ice‐bed interface according to observed ice surface velocities as a model initialization. Then, we drive the model and simulate the changes of ERG from 2010 to 2100. We validate our model by comparing our simulation results to observed ice volume loss during 2010–2020. We find that ERG will reach its maximum meltwater runoff at around 2030 and 2060 for the lower (SSP‐126) and higher (SSP‐585) emission scenarios, respectively. Key Points: We conduct diagnostic and prognostic simulations of East Rongbuk Glacier, Mt. EverestThe use of Robin inversion method during initialization suggests the presence of temperate basal iceWe find East Rongbuk Glacier will likely reach maximum meltwater runoff around the middle of this century [ABSTRACT FROM AUTHOR]

Summer heatwaves over Europe, which can cause many deaths and severe damage, have become increasingly frequent over central and eastern Europe and western Russia in recent decades. In this paper, we estimate the contributions of the warming due to increased greenhouse gases (GHG) and nonlinear variations correlated with the Atlantic Multidecadal Oscillation (AMO) to the observed heatwave trend over Europe during 1980–2021, when the GHG‐induced warming over Europe exhibits a linear trend. It is found that GHG‐induced warming contributes to ∼57% of the European heatwave trend over 1980–2021, while the cold‐to‐warm phase shift of the AMO‐like variations accounts for ∼43% of the trend via the intensification of midlatitude North Atlantic jet. The recent trend of heatwaves over western and northern Europe is mainly due to GHG‐induced warming, while that over central and eastern Europe and western Russia is primarily related to the combined effect of the AMO‐like variations and GHG‐induced warming. To some extent, GHG‐induced warming is an amplifier of the increasing trend of recent AMO‐related European heatwaves. Moreover, European blocking (Ural blocking, UB) is shown to contribute to 55% (42%) of the AMO‐related heatwave trend via the influence of midlatitude North Atlantic jet. In the presence of a strong North Atlantic jet during the recent warm AMO phase, UB events concurrent with positive‐phase North Atlantic Oscillation can cause intense, persistent and widespread heatwaves over Europe such as that observed in the summer of 2022. Plain Language Summary: In recent decades, severe summer heatwaves frequently occurred in Eurasia and North America. However, what leads to the increased European heatwaves in recent decades is still debated. In this paper, we quantify the contributions of greenhouse gases (GHG)‐induced warming and the multidecadal variations correlated with the Atlantic Multidecadal Oscillation (AMO) to increased European heatwaves in recent decades by assuming that GHG‐induced warming shows a linear upward trend. It is revealed that GHG‐induced warming contributes to ∼57% of the recent European heatwave trend during 1980–2021, whereas the cold‐to‐warm transition of the AMO‐like variations contributes to ∼43% of the trend via strengthening the midlatitude North Atlantic jet. In particular, European blocking (EB) (Ural blocking, UB) accounts for ∼55% (42%) of the AMO‐related heatwave trend, even though the area extent and intensity of European heat waves depend strongly on whether the EB or UB is concurrent with the positive phase of NAO and whether the midlatitude North Atlantic jet is strong. Key Points: Severe summer heatwaves frequently occurred in central and eastern Europe and western Russia in recent decadesThe greenhouse gases‐induced warming and the positive phase of Atlantic Multidecadal Oscillation favor increased European heatwavesThe increased quasi‐stationarity, persistence, zonal scale, and slow decay of the European blocking and Ural blocking favor increased duration, extent and intensity of the European heatwaves [ABSTRACT FROM AUTHOR]

Refractory black carbon (rBC) is an important climate‐forcing agent emitted by biomass burning and fossil fuel combustion. Antarctica can receive rBC aerosols emitted in Southern Hemisphere (SH) and preserve the history of emissions and atmospheric transport. Here, we present a high‐resolution record of rBC in an ice core (CA2016‐75) acquired from the coastal Eastern Antarctica, which accumulated during the past 100 years (1915–2015). The rBC concentration (0.030 ng g−1) and flux (7.22 μg m−2 yr−1) are both among the lowest values in Antarctic snow and ice. The rBC concentration reaches higher values on average in the period aligned with the austral Winter. The rBC concentrations show a long‐term descending trend during the period between 1950s and mid‐1990s, followed by an ascending trend to 2015. Back trajectory analysis indicates that the emissions resulting from the biomass burning and anthropogenic biofuel consumption in Southern America and Australia were the main sources for the rBC deposition. Wavelet spectral analysis and temporal correlation analysis on rBC deposition and the atmospheric circulation indices (El Niño–Southern Oscillation, Southern Annular Mode and Antarctic Oscillation) confirmed that the atmospheric circulations have certain influences on the rBC deposition, likely by their direct effects on rBC transport and on weather conditions driving the occurrence of fires and subsequent emissions in source regions. Key Points: Yearly resolution black carbon (BC) data during the past century in east Antarctica were presented and showed the lowest BC values over AntarcticaBC showed a decrease between 1980s and mid‐1990s and then an increase to 2015, the variation was associated with the BC emissions in Southern HemisphereSouthern America, Australia were the potential source regions and the El Niño–Southern Oscillation, Southern Annular Mode both had influences on BC transport and source emissions [ABSTRACT FROM AUTHOR]

Volcanic eruptions have been the most dominant natural forcing of climate change over the past millennium, affecting temperature change at multiple timescales. However, how volcanic eruptions affect regional temperature variability on the decadal timescale remains unclear. We analyzed the bidecadal effects of volcanic eruptions in the mid‐fifteenth century on two representative regions (the Tibetan plateau [TP] and the Arctic) in the Northern Hemisphere by combining proxy reconstructions, model ensemble simulations, and model sensitive experiments. The results show that the TP experienced bidecadal cooling during the mid‐fifteenth century as a result of the long‐term heat uptake in the midlatitude ocean that reduced latent heat transfer to the atmosphere. A positive sea ice–albedo feedback led to a bidecadal summer temperature decrease in the Arctic comparable to that on the TP, whereas the Arctic winter experienced stronger bidecadal cooling caused by a reduced ocean–atmosphere energy exchange and atmospheric poleward energy transport. In addition, our results show that it took ∼20 years for the temperature in these two regions to return to the level that existed before the first eruption, and this was linked to the strengthening of the Atlantic Meridional Overturning Circulation and ocean heat transport. Plain Language Summary: Simulations and reconstructions covering the past millennia show that a period of prolonged cooling developed during the mid‐fifteenth century, and this was related to the volcanic eruptions in the 1450s. We analyzed the influence of the two volcanic eruptions on Tibetan Plateau (TP) and Arctic temperatures through model–data comparison. Our results show that the inertia of the midlatitude ocean dominated the cooling of the TP, whereas the expansion of sea ice led to the cooling of the Arctic and the adjustment of the atmospheric circulation reinforced the cooling of the Arctic winter. In addition, the ensemble simulations indicate that the response of the Atlantic Meridional Overturning Circulation may have ended the period of cooling caused by the volcanic eruptions in the mid‐fifteenth century. This suggests that volcanic eruptions are an important factor that should be considered in the decadal prediction of regional climate and in geoengineering, especially in representative areas such as the TP and Arctic. Key Points: The Tibetan Plateau and the Arctic experienced bidecadal cooling after two volcanic eruptions in the mid‐fifteenth centuryThe heat uptake of the midlatitude ocean caused bidecadal cooling over the Tibetan Plateau after the volcanic eruptionsReduced sea–air energy exchange and atmospheric poleward energy transport led to the Arctic amplification of winter temperature decrease [ABSTRACT FROM AUTHOR]

Using long‐term moorings data together with wind and sea ice measurements, we document the characteristics and variations of upwelling in Barrow Canyon and investigate the upwelled Atlantic Water (AW) on the Chukchi Sea shelf and how it impacts the ice cover. Driven by strong northeasterly winds, upwelling occurs more often in the cold months, and the occurrence tends to increase interannually since 2001. Over the 12‐year mooring record at the mouth of Barrow Canyon, roughly 10% of the upwelling events can drive AW onto the Chukchi Sea shelf. Both AW and non‐AW upwelling events have more occurrence and stronger strength in the cold months, but do not present a significant interannual trend. These variations are associated with the northeasterly winds. Comparing to the non‐AW upwelling, the AW upwelling is generally characterized by more vertical displacement of the AW layer at the mouth of Barrow Canyon, and stronger up‐canyon volume and heat transport. In the ice‐covered period, these two types of upwelling have different consequences for forming polynyas on the shelf. Under similar wind forcing, the ice reduction appears confined in the coastal region in the non‐AW upwelling events, while during AW upwelling events, the sea ice declines dramatically in the shelf interior with 15% more ice loss. It elucidates that the heat carried by the upwelled AW plays a considerable role in modulating the ice cover in the shelf interior. Plain Language Summary: Upwelling in Barrow Canyon brings heat and nutrients that can affect sea ice condition and ecosystems on the Chukchi Sea shelf. In this study, we use mooring data in the vicinity of Barrow Canyon together with the wind data and satellite ice concentration data, to investigate the characteristics and variations of upwelling in the canyon, and how the upwelled warm Atlantic Water (AW) modulates the ice cover on the shelf. Driven by the strong northeasterly winds, the upwelling in the canyon is characterized by an up‐canyon flow and uplifting of water masses, and the upwelling occurrence varies seasonally and interannually. Roughly 10% of the events can upwell the AW onto the Chukchi Sea shelf, which mainly occur in the cold months when the strong northeasterly winds blow. Under similar wind forcing, upwelling of AW leads to the significant ice decrease in the shelf interior, while non‐AW upwelling causes less ice loss that is confined along the coastal region. These discrepancies suggest that the extra heat brought by the AW upwelling in the Barrow Canyon can result in a significant ice loss in the interior of the Chukchi Sea shelf. Key Points: Driven by strong northeasterly winds, upwelling in Barrow Canyon is characterized by up‐canyon flow and vertically uplifted isopycnalsUpwelling of Atlantic Water onto the Chukchi shelf mainly occurs in the cold months when extreme northeasterly wind blowsHeat flux from Atlantic Water upwelling plays an important role in the sea ice loss in the Chukchi shelf interior [ABSTRACT FROM AUTHOR]

Thermokarst lakes and ponds (hereafter referred to as thaw lakes) play an important role in the permafrost regions by regulating hydrology, ecology, and biogeochemistry. However, detailed quantitative information on thaw lake extent and distribution remains poorly resolved across the entire permafrost regions on the Qinghai‐Tibet Plateau (QTP). Here, we applied the random forest (RF) model and manual visual vectorization methods to extract thaw lake boundaries on the QTP based on Sentinel‐2 images. Accuracy assessment was comprehensively demonstrated regarding the inherent spatial resolution of imagery and RF model performance. The results showed that the accumulated uncertainty of the total thaw lake area was ±5.75 km2, and the mean accuracy (91.9%) from field‐measured boundaries of 132 thaw lakes supported the accuracy of this inventory. A total of ∼161,300 thaw lakes with sizes ranging from 500 m2 to 3 km2 were detected, with a total area of ∼2,825.45 ± 5.75 km2. Most thaw lakes were detected in the continuous permafrost type (94.1%) and within the elevations of 4,500–5,000 m (68.4%). The small thaw lakes (<10,000 m2) predominated the total lake number (78.9%) but contributed to a small portion of the total lake area (12.7%). Spatial distributions of thaw lakes in terms of different climatic and environmental conditions were also comprehensively explored, including temperature, precipitation, ground thermal stability, active layer thickness, vegetation, soil properties, and underground ice content. This inventory is expected to be incorporated into Earth system models for a more comprehensive projection of the large‐scale biogeochemical feedback of thermokarst landforms on the QTP under continued global warming. Plain Language Summary: Thaw lakes develop when warming soil melts ground ice, causing the surface to collapse and form pools of water. Such lakes can greatly influence local water resources and ecosystems, but also are important sources of greenhouse gas released into the atmosphere. Using Sentinel‐2 images, we provided robust information of thaw lake numbers, areas, and spatial distributions across the entire QTP permafrost regions by applying the random forest model and manual visual vectorization methods. The accuracy of the data set has been demonstrated in regard to the image spatial resolution, model performance, and field‐measured results. Within sizes ranging from 500 m2 to 3 km2, we extracted ∼161,300 thaw lakes with a total area of ∼2,825.45 ± 5.75 km2. We found that most thaw lakes were located in the continuous permafrost regions and within the elevations of 4,500–5,000 m. Most thaw lake sizes were smaller than 10,000 m2 but they only contributed to a little percentage of the total lake area. We also comprehensively explored the spatial distributions of thaw lakes in different climatic and environmental areas. This inventory would be useful for future Earth system models to predict the large‐scale biogeochemical feedback of thaw lakes on the Qinghai‐Tibet Plateau in the future. Key Points: Using Sentinel‐2 images, we established an inventory data set of thaw lakes on the QTP via random forest model and manual postprocessing methodsApproximately 161,300 thaw lakes with sizes ranging from 500 m2 to 3 km2 were extracted, with a total area of ∼2,825.45 ± 5.75 km2Distributions of thaw lakes were highly uneven in regard to different geospatial, climatic and environmental status [ABSTRACT FROM AUTHOR]

Plain Language Summary: Melting of the Antarctic ice sheet and shelf in the future will be influenced by interannual changes in the surface air temperature (SAT) in Antarctica. The SAT changes in Antarctica are related to variations in the Southern Hemisphere Annular Mode (SAM) during the austral summer. The SAM is a dominant pattern of atmospheric variability in the Southern Hemisphere and influences the Antarctic SAT with opposite changes between the northern Antarctic Peninsula (AP) and Eastern Antarctica (EA). To project future changes in the Antarctic SAT, we analyzed historical and future simulations from the Climate Model Intercomparison Project 5 models. We found that the degree of opposite interannual SAT changes between EA and the AP increases in the future due to intensified magnitude of the SAM‐related circulation anomalies, and summers of warmer SAT in the northern AP and cooler SAT in EA increase by 4% in the future compared to the historical period. This finding has major consequences for glacier melting in the northern AP in the future because more days of extremely high SAT in the northern AP may occur in the future. In this study, using the Climate Model Intercomparison Project 5 (CMIP5) simulations and by empirical orthogonal function (EOF) analysis, the first mode of variability in interannual surface air temperature (SAT) in Antarctica (EOF1) was examined for the period between 1979–2004 and 2051–2099 during the austral summer. The ensemble mean of EOF1 of the CMIP5 models shows a positive SAT anomaly over the northern Antarctic Peninsula (AP) and a negative SAT anomaly over Eastern Antarctica (EA) in both periods. A poleward expansion of the AP positive anomaly and an increase in the negative anomaly over interior EA are expected in 2051–2099, resulting in a larger difference of interannual SAT between interior EA and the AP in 2051–2099 than in 1979–2004. The increasing difference in the interannual SAT is consistent with a larger magnitude of the SAM‐related circulation anomalies in the future. Key Points: An increasing summer interannual surface air temperature (SAT) variability in interior Eastern Antarctica (EA) and the Antarctic Peninsula (AP) simulated in 2051–2099An increasing difference in summer interannual SAT between EA and the AP simulated in 2051–2099 than in 1979–2004The increasing difference in summer interannual SAT caused by a larger Southern Hemisphere Annular Mode‐related circulation anomaly in 2051–2099 than in 1979–2004 [ABSTRACT FROM AUTHOR]

The sensitivity of the Arctic precipitation phases (solid and liquid) to the forcings from greenhouse gases (GHGs) and aerosols over 2016–2080 was investigated by using the Community Earth System Model Version 1. Results show that the warming caused by the two forcings results in an increasing trend in total precipitation and a solid‐to‐liquid precipitation transition in the Arctic. Under RCP8.5 scenario, the increased rate of Arctic mean precipitation with global warming forced by aerosol reduction (7.7%/°C) is twice greater than that by increased GHG emission (3.5%/°C). The sensitivity of rainfall to precipitation ratio (RPR) to various forcings is much higher than that of total precipitation in the Arctic. The increased rate of RPR due to global aerosol forcing (8.4%/°C) is approximately 3 times that due to GHG forcing (2.9%/°C) in the Arctic, the differences even larger over Greenland and the eastern Arctic Ocean, resulting in more rainfall in these areas. Plain Language Summary: The precipitation phase is extremely sensitive to temperature changes, especially in the Arctic. Solid and liquid precipitation have almost the opposite effect on the ground energy budget. The changes in precipitation phase can greatly affect snow and ice mass balance, regulating the regional hydrological cycle. The transition from solid precipitation to liquid precipitation can even promote carbon release over the permafrost through changing the rate of snow melting. We evaluated the impacts of the two most important anthropogenic forcing agents (greenhouse gases [GHGs] and aerosols) on the changes of precipitation phases in the Arctic using a state‐of‐the‐art Earth system model. We found that the warming forced by global aerosol reduction and increased GHG emission leads to a solid‐to‐liquid precipitation transition and therefore more rainfall events in the Arctic. Under RCP8.5 scenario, the sensitivity of Arctic precipitation phase to global aerosol forcing is approximately 3 times that to the GHG forcing, and the most sensitive phase changes of Arctic precipitation to the aerosol forcing are observed in Greenland and the eastern Arctic Ocean. Understanding the impact of human activities on the changes in the Arctic precipitation phase will help formulate reasonable emission reduction policies and better adapt to the rapid Arctic climate changes in the future. Key Points: Warming forced by global aerosol reduction and increased GHG emission leads to a solid‐to‐liquid precipitation transition in the ArcticThe sensitivity of Arctic precipitation phase to the aerosol forcing is approximately three times that to the GHG forcingThe most sensitive phase changes of Arctic precipitation to the aerosol forcing are observed in Greenland and the eastern Arctic Ocean [ABSTRACT FROM AUTHOR]

Anthropogenically induced climate warming will not stop as long as carbon dioxide (CO2) emissions continue to increase. As positive feedback from the cryosphere can amplify climate warming in higher latitudes, adaptation to and mitigation of climate change in the cryosphere have become particularly important. In this study, we quantified the contributions of climate policies of the developed and developing worlds to moderating decreases in Northern Hemisphere sea ice and snow, using the Earth System Model of Beijing Normal University (BNU‐ESM). The results indicate that the sea ice extent and snow cover would continue to shrink as CO2 concentrations continue to increase, and the combined efforts of the developed and developing worlds could successfully reduce losses of Arctic sea ice and snow. In the medium term (before 2060), contributions of the developing world to reducing the loss of Arctic sea ice extent are expected to be 65% in JFM and 60% in JAS, while the corresponding contributions to reducing snow cover loss are 46 and 70%. These contributions from the developed world are smaller: 44% in JFM and 22% in JAS for sea ice extent and 34% in JFM and 20% in JAS for snow cover. Over the long term (until 2100), the developing world is expected to contribute 71% in JFM and 77% in JAS to reducing the Arctic sea ice losses, and its contribution to reducing snow cover loss is 73 and 66%. Similarly, the corresponding contribution for the developed world is also smaller: 36% in JFM and 24% in JAS for sea ice extent and 32% in JFM and 30% in JAS for snow cover. However, the developed and developing world achieves a combined mitigation effect of more than 90% in the near and long term. [ABSTRACT FROM AUTHOR]

Using automatic weather station and reanalysis data (ERA5) from 2011 at Panda‐1 Station, situated in the katabatic region of Princess Elizabeth Land, East Antarctica, the surface energy balance was calculated using a surface temperature iteration method, and the characteristics of each energy component were analyzed. Downward shortwave and longwave radiation were the two primary energy sources during summer days with seasonal means of 346 and 142 W m−2. The turbulent fluxes of sensible and latent heat flux represent smaller heat sources. In the annual mean, reflected shortwave radiation exceeds the upward longwave radiation with a seasonal average values of −287 W m−2. During winter, the shortwave radiation is small, and the main energy input and output terms of the surface energy balance are downward and upward longwave radiation, with seasonal average values of 149 and −159 W m−2, respectively. The combination of high wind speed and a large near‐surface humidity gradient during summer resulted in significant frost depositional events. The total surface frost deposition for the whole year was 24 kg m−2, which accounted for 61% of the total accumulation (averaged over 10 years). When a high‐pressure ridge blocks cyclones and deflects fronts of low‐pressure systems to inland East Antarctica during winter, this has a significant impact on the surface energy balance at Panda 1 automatic weather station, with daily sensible and latent heat fluxes increasing by as much as 25 and 12 W m−2, respectively. These results still contain uncertainties as we only address a single year, when interannual variability may be considerable, and we do not consider drifting snow sublimation. Key Points: Data from Panda 1 AWS and ERA5 reanalysis from 2011 were used to estimate the surface energy balance in the typical katabatic wind zone of East AntarcticaThe influence of two warm and moist air intrusions from the Southern Ocean on the surface energy balance is presentedBetter SEB algorithm scheme in Katabatic areas of Antarctica is validated and promoted [ABSTRACT FROM AUTHOR]