ALBERT

Description: Mathematics Education; Learning; Teaching

Description: Arctic clastic coastlines are some of the most dynamic in the world and have a large impact on cultural and natural resources. Sea ice plays an important role in the erosion and accretion dynamics of these coastlines, and sea ice cover is currently declining at 〉10% per decade. As a result of declining sea ice cover and an increase in the duration of open water days in the Arctic Ocean, we need to know more about coastal processes in polar seas, specifically how sea ice decline changes coastal processes, the rate at which such coastal changes can occur, and how the effects of declining sea ice interacts with local coastline characteristics including wave fetch, bathymetry, permafrost properties onshore, and pre-existing coastal geomorphology. To assess the influence of sea ice decline on permafrost coastal dynamics we selected two segments of the coastline in NW Alaska with contrasting geography, surficial geology and geomorphology. Study site A, Cape Krusenstern National Monument (CAKR), has a wave-dominated, west- to south-west facing, coarseclastic shoreline. Accreted beach ridges, barrier-closed lagoons, permafrost bluffs, longshore gravel bars, and gravelly beaches characterize coastal geomorphology. Study site B, the Bering Land Bridge National Park and Preserve (BELA), has a north-facing coastline with a shoreline characterized by yedoma and thermokarst basin permafrost bluffs, aggrading spits, sandy barrier islands, and open lagoons. To establish rates of coastal change and identify key geomorphological processes, we digitally mapped the shoreline of both study areas using aerial photographs (1-meter resolution or better) and sub-meter resolution World View-2 satellite imagery from 2003 and 2014, respectively. We compared our data to the results of previous studies based on imagery taken between 1950 and 2003 (Lestak et al., 2010). To better understand the relationship between geomorphology and rates of change, we established geomorphological landform classes for both study areas. We mapped coastal changes within a subset of each study area, using sub meter resolution imagery, over annual time steps to help us better quantify variations in the rate of event driven coastline change. Mapping results for the period 2003 to 2014 suggest a change in erosion rates within both study sites. Erosion rates for the period 1950 to 2003 in BELA and CAKR were -0.12 m/yr and -0.98 m/yr respectively, where the negative signs indicate shoreline retreat (Gorokhovich and Leiserowiz, 2012). These rates, for the period between 2003 and 2014, increased in CAKR to -0.86 and decreased in BELA to -0.69 m/yr. Rates of erosion were found to vary according to geomorphology, with overwash fans in BELA exhibiting the highest rates of change at -1.3 m/yr. Significant changes in geomorphology were observed for this time period including the development of a 200-meter long spit in CAKR, degradation of ice wedges on upland yedoma bluffs in BELA, and the infilling of numerous barrier island ponds due to overwash events in BELA. Our results illustrate the complexity of coastal responses along Arctic coastlines even within close proximity. To ensure robust projections of future coastal change, further mapping and analysis at intraannual and sub-meter spatial resolution is necessary to firmly tie together cause and effect of arctic coastal processes with a changing climate. References: 1. Gorokhovich, Y., Leiserowiz, A., 2012. Historical and Future Coastal Changes in Northwest Alaska. J. Coast. Res. 28, 174–186. 2. Lestak, L.R., Manley, W.F., Parrish, E.G., 2010. Digital Shoreline Analysis of Coastal Change in Bering Land Bridge NP (BELA) and Cape Krusenstern NM (CAKR), Northwest Alaska: Fairbanks, AK: National Park Service, Arctic Network I&M Program. Geospatial Dataset-2184176.

Description: Some of the highest coastal erosion rates in the world are now occurring along non-bedrock, permafrost affected coastlines in the Arctic. Understanding how vulnerable Arctic coastlines are to current and future climate change is critical for resource management, subsistence hunting and gathering, and quantifying the flux of carbon and sediment from a terrestrial to marine environment. Observations since the 1970’s, show that pan-Arctic sea ice extent is decreasing by approximately 12 % per decade, with 2012 exhibiting the longest ice-free season on record. As a result, Arctic coastlines are vulnerable to wave-driven erosion for longer periods. Permafrost borehole temperatures show an overall warming trend, increasing susceptibility to thaw. While several studies already exist pointing at accelerating coastal erosion along the Beaufort Sea coast, studies for the Chukchi Sea coast of NW Alaska have remained inconclusive for the 1950-2003 period. Did recent dramatic changes in sea ice extent, with several sea ice minimum records since the mid 2000’s have an impact on the patterns and processes of coastal dynamics of the Chukchi Sea coast? Here we report on coastal change rates and key geomorphological processes occurring between 2003 and 2013 in comparison to coastal dynamics between 1950 and 2003 along the northern shoreline of the Seward Peninsula, Alaska, USA. Previous studies in our study area, focusing on 1950 to 2003, show rates of change ranging from -5.84 to 2.57 meters per year, indicating the occurrence of both erosion and aggradation. Our study shoreline is a complex system of barrier islands, sand spits, yedoma bluffs and drained thermokarst lake basins. The 1950-2003 coastal change data is based on aerial imagery covering 3 time steps (ca. 1950, ca. 1978, and 2003) that was analyzed by Lestak et al. 2010. To place recent coastal change dynamics since then in a spatial context, we conducted geomorphological analysis using 22 sub-meter resolution panchromatic World View 2 images from June 2013 and a five-meter resolution interferometric synthetic aperture radar derived digital elevation model acquired in summer 2012. We identified key geomorphological processes associated with coastal change and analyzed sediment redistribution between yedoma bluffs, lagoons and spits. Although relatively stable, ice wedge degradation was observed in yedoma bluff areas. Barrier islands, tidal channels, and overwash deposits showed significant variation in morphology during the study period. We further collected weather station data from Shishameref and Kotzebue, the two closest climate stations to the study area, and plan to extract sea ice and sea surface temperature data for the immediate region offshore our study coast. Our results illustrate the heterogeneous nature of coastal dynamics along the Arctic coastline and the need to acknowledge this when modelling future coastal response to sea ice decline and climate change.

Description: Perennially frozen ground and sea ice are key constituents of permafrost coastal systems, and their presence is the primary difference between temperate and high-latitude coastal processes. These systems are some of the most rapidly changing landscapes on Earth and, in the Arctic, are representative of the challenges being faced at the intersection between natural and anthropogenic systems. Permafrost thaw, in combination with increasing sea level and decreasing sea-ice cover, exposes arctic coastal and nearshore areas to rapid environmental and social changes. Based on decadal timescales, observations in the Arctic indicate an increase in permafrost coastal bluff erosion and storm surge flooding of low-lying ice-rich permafrost terrain. However, circum-arctic observations remain limited and the factors responsible for the apparent increase in arctic coastal dynamics are poorly constrained. A better understanding of permafrost coastal systems and how they are responding to changes in the Arctic is important since a high proportion of Arctic residents live on or near coastlines, and many derive their livelihood from terrestrial and nearshore marine resources. An expanding industrial, scientific, and commercial presence in the Arctic Ocean will also require advanced knowledge about permafrost coastlines as terrestrial access points. Since the issues involved span political, cultural, geographical, and disciplinary borders, an international network focused on permafrost coastal systems in transition is needed. An integrative network focused on permafrost coastal systems is required to realize and address the scale and complexity of the processes, dynamics, and responses of this system to physical, ecological, and social change. A primary focus of such an effort would be guided by the fact that the issues and impacts associated with permafrost coastal systems in transition are far greater than any single institution or discipline is capable of addressing alone. Future permafrost coastal system dynamics will challenge conventional wisdom as the system enters a new state impacting human decision making and adaptation planning, cultural heritage resources and ecosystems, and likely resulting in unforeseen challenges across the Arctic.