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.

北极气候正发生变化，致使富含冰的永久冻土（ice-rich permafrost）海岸陡崖的退缩速率不断加快。在阿拉斯加博福特海（Beaufort Sea）沿岸，侵蚀速率自1955年以来已增长约三倍，从每年6.8米升至19米；而无海冰季时长自1979年以来也增长约两倍，从45天增至100天。我们开发了一款陡崖退缩数值模型，以评估无海冰季时长、海平面、水温、近岸波场（nearshore wavefield）及永久冻土温度在该区域控制侵蚀速率的相对作用。该模型复现了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（melt notches）的演化、冰楔约束块体的坍塌以及此类块体的退化。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良好。侵蚀具有极强的偶发性，近40%的侵蚀发生在不足5%的无海冰季时段内。在我们评估的多款海底侵蚀速率计算公式中，我们推荐同时结合水温与近岸波场的公式。由于高水位是侵蚀发生的前提条件，未来任何能提升水位超过陡崖基底频率的变化，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，均会促成这一效应。此外水温也会对侵蚀速率产生影响，若无海冰季进一步扩展至日照最强的仲夏时段，可能会进一步推高海岸退缩速率。本数据集包含2009年至2010年在阿拉斯加德鲁角（Drew Point, AK）附近，由Anderson、Overeem与Wobus研究员收集的水位、水温和波场观测数据，研究过程中得到了Adam LeWinter的协助。该数据曾被Barnhart等人于2014年发表的论文使用：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/观测点/船舶信息：观测点的分布图可参见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。