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Greenland surface mass balance (SMB) is undergoing dramatic change due to the amplified Arctic warming, with more frequent record‐breaking melt events. To comprehensively understand the behaviour of the Greenland ice sheet, we develop a suite of indices to examine the spatiotemporal variations of extreme events in SMB over Greenland during 1958–2019 based on the RACMO2.3p2 model outputs. We illustrate that the climatological distributions of extreme ablation‐dominated events (i.e., extremes with SMB < 0) share large similarity with the mean SMB in terms of intensity and frequency, showing a coastal‐to‐inland decreasing pattern. This pattern holds for the intensity of the extreme accumulation‐dominated events (i.e., extremes with SMB > 0), but not for the frequency which increases from the coastal to inland Greenland. Regarding the temporal evolution, the intensity and frequency of extreme ablation‐dominated events show a decreasing trend over Greenland during 1958–1978, whereas the trend increases afterwards, especially during the last two decades (2001–2019). However, these trends fluctuate regionally across the GrIS both in terms of magnitude and sign, with the most pronounced variations occurring in southwest Greenland. In contrast, extreme accumulation‐dominated events show, on average, a long‐term increasing trend from 1958 to 2019 in terms of intensity and frequency. However, obvious spatial fluctuations exist across the GrIS during 1958–2019, especially between the southwest and northeast Greenland where an opposite trend is observed. Additionally, the variations of SMB extremes in boreal summer are linked with the changes in regional temperature and precipitation and the associated atmospheric circulations, and the dominating factor varies with different extreme indices and time intervals. Our results may advance our understanding on SMB variability over Greenland and contribute to the design of future Greenland observational networks. [ABSTRACT FROM AUTHOR]

The Asian–African monsoonal precipitation (AAMP) has a significant impact on the water availability, biodiversity, and livelihoods of billions of people. A comprehensive understanding of the AAMP behavior over Earth's history will help to make better future projections. Using a set of transient climate simulations over the last 21 000 years (21 ka), the variation of the AAMP and its responses to various external forcings, including orbital insolation, greenhouse gases (GHGs), and ice sheets, are explored. The precipitation evolutions in the individual monsoon domains have the characteristic of hemispheric synchrony over the last 21 ka. Specifically, the AAMP increased from the Last Glacial Maximum to the early Holocene with several abrupt events and then decreased subsequently. The raised orbital insolation and GHGs lead to an overall AAMP increase, but the enhanced insolation tends to induce a systematic northward shift of the Asian–African monsoon domain. Decreased meltwater discharge could promote the African and Indian monsoonal precipitation through strengthening the Atlantic Ocean meridional overturning circulation. However, the lowering of ice sheets (i.e., orographic effect) results in an anomalous dipole precipitation pattern between North China and India. An analysis of the moisture budget suggests that, although different external forcings may lead to the same sign of precipitation change (e.g., both increased insolation and GHGs can cause the enhanced AAMP), the thermodynamic and dynamic contributions to precipitation could vary greatly by region and forcing. This study provides a reference for the long-term behavior of the AAMP with rising GHGs, higher insolation, and potential melting of the Greenland Ice Sheet. [ABSTRACT FROM AUTHOR]

One of the key uncertainties in future sea-level projections is attributed to the Greenland ice sheet (GrIS). Studying the response of the GrIS to climate changes during the past warm periods is helpful for understanding future changes in the GrIS. In this study, using three global climate models (Community Atmosphere Model version 3.1 and version 4.0 and Norwegian Earth System Model) and a three-dimensional ice sheet model, we investigate the climate and ice sheet changes over Greenland during the mid-Pliocene warm period (~3 Ma bp). The results show that the regionally averaged summer temperature over Greenland is 9.4-13.4 °C higher during the mid-Pliocene period than during the pre-industrial era and the annual mean precipitation is 65.2-108.3 mm a greater. In response to this warm-wet climate, the GrIS shows a substantial decrease in size during the mid-Pliocene, with little ice existing along the eastern coast of Greenland. Compared to that simulated in the control run, the global sea level is approximately 7.8-8.1 m higher during the mid-Pliocene due to the decrease in the size of the GrIS. In addition, paleoclimate proxies also indicate that it is unlikely that a large-scale ice sheet exists over Greenland during the mid-Pliocene warm period. [ABSTRACT FROM AUTHOR]