南极Getz冰架夏季表面温度时空变化及驱动因素分析

Spatiotemporal Variations and Drivers of Austral Summer Surface Temperature over the Antarctic Getz Ice Shelf Based on FY-3 Satellite Data

  • 摘要: Getz冰架是南极第八大冰架,表面融化潜力较高。冰雪表面温度是表征冰架表面能量收支和物质平衡的关键参数。国产风云三号(FengYun-3,FY-3)系列卫星搭载的中分辨率光谱成像仪(medium resolution spectral imager, MERSI)数据具有大幅宽、高空间分辨率的优势,但目前在南极冰架表面温度监测中的应用尚不充分。基于FY-3A MERSI-I及FY-3D MERSI-II热红外遥感数据,反演获得该冰架2008-2014年及2019-2024年夏季(10月至次年3月)250 m空间分辨率的冰雪表面温度数据,并分析其时空变化及驱动因素。时序分析显示,两个时段内冰雪表面温度均无明显变化趋势,但2013年3月观测到一次超过5 K的异常增温事件。该事件由阿蒙森海的反气旋驱动暖湿气流向极输送所致,这一过程引起中低云覆盖增加,增强了向下长波辐射,导致地表快速增温。在空间分布上,冰架中部靠近接地线区域偏暖,偏暖区域面积占冰架总面积的8.51%,该偏暖主要受下降风带来的感热输送影响,有效风速与偏暖强度的皮尔逊相关系数为0.51(p < 0.01)。冰架西侧也呈现偏暖特征,与冰裂隙密集导致的低反照率相关。低反照率增强了净短波吸收,使冰雪表面温度升高,年融化天数增加约20%。这一过程揭示了冰裂隙对冰架表面融化的驱动作用,可能增加冰架崩解风险。分析结果显示,FY-3 MERSI数据在南极冰架表面温度精细化监测中存在优势,为理解Getz冰架表面温度的时空变化提供了新的认识。

     

    Abstract: Objectives: The Getz Ice Shelf, Antarctica’s eighth largest, is a region of high surface melt potential, projected to be a melt hotspot throughout this century. Meltwater can lead to ice shelf deformation, hydrofracturing and disintegration, processes that are directly linked to the ice surface temperature (IST). IST is a critical indicator of its surface energy budget and mass balance. Chinese FY-3 MERSI series data possess the advantages of a wide swath and high spatial resolution, but their application in Antarctic ice shelf surface temperature monitoring is currently insufficient. Therefore, the objective is to retrieve high-resolution IST over the Getz Ice Shelf using FY-3 MERSI data and to investigate its spatiotemporal variations and driving factors. Methods: We applied the MERSI-ISC algorithm to FY-3A MERSI-I (2008–2014) and FY-3D MERSI-II (2019–2024) data to retrieve austral summer (October to the following March) IST over the Getz Ice Shelf at a 250 m spatial resolution. The algorithm adopted a directional emissivity to correct the retrieval errors caused by the wide range of sensor viewing angles (0–70°) in MERSI. Real-time atmospheric water vapor content is retrieved directly from MERSI data. An atmospheric correction scheme is developed for the thermal infrared band of MERSI under polar atmospheric conditions. The IST is subsequently calculated directly using the Planck’s equation. Time-series IST variation data were obtained through fitting and statistical analysis by introducing the annual temperature cycle model. Following validation with automatic weather stations data and cross-comparison with MODIS IST, we analyzed the IST’s spatiotemporal variations, characterized significant warm events, and investigated the underlying driving factors. Results: (1) Validation based on data from automatic weather stations shows an RMSE of 2.01 K. Cross-validation against MODIS IST indicates a discrepancy of merely 0.19 K between MERSI-I and MERSI-II retrieval results, suggesting good inter-sensor consistency in IST retrieval. (2) Time series analysis reveals that the mean summer IST was 257.68 K during 2008–2014 and 258.04 K during 2019–2024, with neither period exhibiting a statistically significant trend. However, an anomalous warming event exceeding 5 K was observed in March 2013, abruptly reversing the typical seasonal cooling and resulting in a higher monthly average IST for March than for February. Meteorological analysis linked this anomaly to an anticyclone in the Amundsen Sea, which drove strong poleward transport of moisture and heat. The consequent increase in mid- and low-level cloud cover enhanced longwave radiation, leading to rapid surface warming. (3) Spatially, the relatively warmer signals were observed in the central sector near the grounding line, with the warm area accounting for 8.51% of the total ice-shelf area. This warming was primarily driven by sensible heat flux associated with katabatic winds. Pronounced warming corresponded to higher wind speeds, as enhanced wind speeds significantly strengthened the sensible heat flux. The Pearson correlation coefficient between effective wind speed and warming intensity was 0.51 (p < 0.01). Furthermore, the heavily crevassed western part of the ice shelf exhibited lower albedo. This reduction amplified net shortwave radiation absorption, leading to higher IST, and an approximately 20% increase in annual melt days. A strong negative correlation between albedo and IST (R = -0.89, p < 0.01) further corroborates the aforementioned mechanism. This process highlights how crevasses amplify surface melting and potentially increase the risk of ice shelf disintegration. Conclusions: These findings demonstrate the potential of FY-3 MERSI data, with their wide swath and high spatial resolution, for refined monitoring of thermal variability of Antarctic ice shelves, and provide new insights into the spatial patterns and driving factors of IST and warm events on the Getz Ice Shelf.

     

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