Nearshore oceanographic observations at Drew Point, Alaska, Summers 2009 and 2010

The Arctic climate is changing, inducing accelerating retreat of ice-rich permafrost coastal bluffs. Along Alaska’s Beaufort Sea coast, erosion rates have increased roughly threefold from 6.8 to 19 m per yr since 1955 while the sea ice-free season has increased roughly twofold from 45 to 100 days since 1979. We develop a numerical model of bluff retreat to assess the relative roles of the length of sea ice-free season, sea level, water temperature, nearshore wavefield, and permafrost temperature in controlling erosion rates in this setting. The model captures the processes of erosion observed in short-term monitoring experiments along the Beaufort Sea coast, including evolution of melt notches, topple of ice wedge-bounded blocks, and degradation of these blocks. Model results agree with time-lapse imagery of bluff evolution and time series of ocean-based instrumentation. Erosion is highly episodic with 40% of erosion is accomplished during less than 5% of the sea ice-free season. Among the formulations of the submarine erosion rate we assessed, we advocate those that employ both water temperature and nearshore wavefield. As high water levels are a prerequisite for erosion, any future changes that increase the frequency with which water levels exceed the base of the bluffs will increase rates of coastal erosion. The certain increases in sea level and potential changes in storminess will both contribute to this effect. As water temperature also influences erosion rates, any further expansion of the sea ice-free season into the midsummer period of greatest insolation is likely to result in an additional increase in coastal retreat rates. This dataset includes observations of water level, water temperature, and wave field collected in 2009 and 2010 near Drew Point, AK by investigators Anderson, Overeem, and Wobus, with help from Adam LeWinter. This data was used in a publication published in 2014 by Barnhart et al. Barnhart, K. R., R. S. Anderson, I. Overeem, C. Wobus, G. D. Clow, and F. E. Urban (2014), Modeling erosion of ice-rich permafrost bluffs along the Alaskan Beaufort Sea coast, Journal of Geophysical Research Earth Surface, 119, doi:10.1002/2013JF002845. Platform/Station/Site/Ship Information: A map of the sites can be found in Figure 2 of Barnhart et al. (2014). Exact latitude/longitude locations and temporal durations for each instrument is provided in the attached README.北极气候正发生显著变化，致使富冰多年冻土（ice-rich permafrost）海岸陡崖的后退速率持续加快。在阿拉斯加博福特海（Beaufort Sea）沿岸，自1955年以来，海岸侵蚀速率已从每年6.8米升至19米，增幅约达三倍；而自1979年起，无海冰季（sea ice-free season）时长已从45天增至100天，增幅约达两倍。 我们开发了一款陡崖后退数值模型，用以评估无海冰季时长、海平面、海水温度、近岸波场（nearshore wavefield）以及多年冻土温度在调控该区域侵蚀速率中的相对作用。该模型可复现博福特海沿岸短期监测实验中观测到的各类侵蚀过程，包括融蚀凹槽的发育、冰楔束缚块体的倾倒以及此类块体的降解。模型结果与陡崖演化的延时影像（time-lapse imagery）及海洋观测仪器的时间序列数据吻合度良好。 侵蚀过程具有高度偶发性：约40%的总侵蚀量发生在不足5%的无海冰季时段内。在我们评估的多种海底侵蚀速率计算公式中，我们推荐同时采用海水温度与近岸波场的公式。由于高水位是侵蚀发生的先决条件，未来任何能提升水位超过陡崖基部频率的变化，都将加剧海岸侵蚀速率。海平面的必然上升以及风暴活动的潜在变化，均会推动这一效应。此外，海水温度同样会影响侵蚀速率，若无海冰季进一步扩展至日照最强的仲夏时段，则可能进一步推高海岸后退速率。 本数据集包含2009年与2010年，由Anderson、Overeem与Wobus团队在阿拉斯加德鲁角（Drew Point, AK）附近采集的水位、海水温度与波场观测数据，亚当·勒温特（Adam LeWinter）提供了辅助工作。本数据曾被Barnhart等人于2014年发表的研究使用：Barnhart, K. R., R. S. Anderson, I. Overeem, C. Wobus, G. D. Clow, and F. E. Urban (2014), Modeling erosion of ice-rich permafrost bluffs along the Alaskan Beaufort Sea coast, *Journal of Geophysical Research: Earth Surface*, 119, doi:10.1002/2013JF002845。 平台/站点/船舶信息：相关站点分布图可参见Barnhart等人(2014)的图2。各仪器的精确经纬度坐标与观测时段详见随附的README文件。