Borns 2016 Minipapers Year 24
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The Arkansas River Glacial Lake Outburst Flood Problem: Geomorphological Evidence and Modeling with HEC-RAS Xavier Allègre1, Roger LeB. Hooke1, 2 1. School of Earth and Climate Sciences, University of Maine. 2. Climate Change Institute, University of Maine. Abstract: During the late Pleistocene glaciers extended across the Arkansas River valley, Colorado, damming the river and forming a lake. Flood boulders on terraces downstream from the lake suggest at least two flood events. We propose to model these floods to learn more about water depth downstream of the dam breach, and thus possibly reduce future disasters elsewhere. Setting: crossed the Arkansas River and slammed into Keenan Lee (Lee 2008) was one the first (with the Mosquito Range on the east side of the Scott, 1975) to find evidence for glacial lake valley. These ice rafted boulders give evidence outburst floods in the Arkansas River valley, of the extent of water at the moments of the Colorado, during the Pleistocene. outburst floods, but this evidence does not Flood landforms are features of these constrain the depths of the floods sufficiently catastrophic events. Landslides (namely Kobe, well. Mt Massive and Empire Gulch landslides) also occurred at the same time as the floods, owing Objectives: to a reversed hydraulic gradient. Lakes HEC-RAS is an open-source software impounded behind the glacial dam did not cut developed by the USGS that can be used to clear shorelines, but ice rafted boulders dropped reconstruct these floods. It has been used by from icebergs, both in the lake basin and Jürgen Herget (2005) to constrain Pleistocene clustered on shore, are the testimony to the ice-dammed lake outburst floods in the Altai previous extent of these lakes. Mountains, Siberia. Our goals are similar to his and we will try to follow a similar methodology to model the water depth downstream from the dam breach. We primarily need to incorporate cross-sections, with a chosen spacing, from a map of the Arkansas River valley into the software, starting downstream and proceeding upstream. Initially we will use Brugger et al.'s (2010) estimates of discharge. Bibliography: Brugger, K. et al. (2010). Discharge estimates for a glacial outburst Paleoflood on the Upper Arkansas River, Colorado, from an ice dam failure model, GSA poster. Fig. 1. Geographical settings: Three glaciers lake Herget, J., 2005. Reconstruction of Pleistocene impounded by a glacial dam formed by northern Clear ice-dammed lake outburst floods in the Altai Creek and southern Pine Creek glaciers during Mountains, Siberia: GSA Spec Pap., 386 118pp. Pleistocene, figure taken from (Lee 2008). Lee, K. (2008). Three glaciers flood Arkansas River, Colorado. Unpub ms dated 8/21/2008. The origin of this debris that provides a way to reconstruct the extent of the glacial lakes is the Scott, G.R., 1975, Reconnaissance geologic same as that of boulders that we find now map of the Buena Vista Quadrangle, Chaffee downstream: The Sawatch Range, hosted and Park Counties, Colorado: USGS Miscel glaciers flowing from the west; these glaciers Field Studies Map MF-657, scale 1:62,500. Atmospheric Circulation Influences on West Greenland Precipitation Jeffrey D. Auger1, Sean D. Birkel1, Kirk A. Maasch1,2, Keah C. Schuenemann3, Paul A. Mayewski1,2 1. Climate Change Institute, University of Maine. 2. School of Earth and Climate Sciences, University of Maine. 3. Earth and Atmospheric Sciences, Metropolitan State University of Denver. Abstract: This preliminary study uses the 56-year Japanese Meteorological Agency Reanalysis to examine the influence of North Atlantic teleconnections on precipitation over West Greenland. Recent decades have brought significant warming point to synoptic patterns that influence precipitation and glacier retreat to West Greenland. By in this region. understanding changes in atmospheric circulation that deliver heat and moisture to the region, we may In summary, our results thus far suggest that the gain valuable insight into future climate and sea- influences from the AMO and NAO on West level rise. Two centerpiece patterns over the North Greenland precipitation are complex. The AMO Atlantic Basin, the Atlantic Multidecadal Oscillation warm phase does show a minimal increase of (AMO) and North Atlantic Oscillation (NAO), play a precipitation with respect to the previous AMO-cool major role in global climate (Parker et al., 2007). phase. A link with NAO exists, but only during The impact of the NAO and AMO on West extreme years of precipitation. Although we cannot Greenland remains less well understood. Here, we fully explain West Greenland precipitation with just present results from a preliminary examination of the AMO and NAO, it is clear by default that other these North Atlantic teleconnections using JRA-55 variables such as location of moisture flux sources (Kobayaski et al., 2015), a state-of-the-art and synoptic blocking patterns in the North Atlantic reanalysis model spanning 1958-present. domain are potentially relevant. The AMO defines the fluctuation (~70 year period) of average sea surface temperature (SST) in the North Atlantic Basin from 0-70 N, whereas the NAO defines synoptic modes of atmospheric circulation arising from the sea level pressure difference between the Azores High (AH; measured at Lisbon, Portugal) and Icelandic Low (IL; measured at Reykjavik, Iceland). These climate patterns are linked on decade timescales such that cool SSTs (- AMO) facilitate +NAO like patterns and warm SSTs (+AMO) facilitate -NAO like patterns. The signal of West Greenland precipitation from West Greenland Precip JRA-55 shows that moisture delivery to the region 5-year Running Avg increased by ~8% during the most recent transition from AMO-cool to AMO-warm (Fig. 1). The NAO shows a different story on the annual timescale. Fig. 1. West Greenland (upper left corner) precipitation Years with totals of extreme high precipitation registered in the JRA-55 record, 1958-2013 (thin, black line) (1983, 1996, 2005, and 2012) show high-pressure with a 5-year running average (thick, black line). Red (blue) blocking events thereby weakening the pressure dots show 4 years of minimum (maximum) precipitation. Red gradient between the IL and AH. Moreover, the IL is and blue lines show average total annual precipitation during the AMO warm and cool phases, respectively. weaker when compared to the four years with extreme low precipitation (1958, 1974, 1992, and Acknowledgements: This work is supported by NSF 2009), showing a relatively deeper IL. A deeper IL award PLR-1417640 (GreenTrACS) to Sean Birkel. is due to dominantly zonal flow bringing moisture Bibliography: eastward to Europe rather than to West Greenland. Kobayashi, S., [and others], The JRA-55 Reanalysis: Although precipitation in West Greenland does not General Specifications and Basic Characteristics. J. Met. correlate well with the NAO index, the link between Soc. Japan 93 (2015): 440. the extreme precipitation years and the NAO does Parker, D. [and others], Decadal to multidecadal variability and the climate change background. J. Geophys. Res. 112 (2007): D18115. Investigating Ecological Values of Rockweed Habitat to Intertidal Invertebrates along the Maine Coast Amy M. Baron1,2, Amanda Klemmer1,3, and Brian J. Olsen2,3 1. Ecology and Environmental Sciences, University of Maine. 2. Climate Change Institute, University of Maine. 3. School of Biology and Ecology, University of Maine. Abstract: Rockweed (Ascophyllum nodosum) provides many essential ecological services to the Maine intertidal ecosystem, including habitat for many species. However, increasing commercial rockweed harvesting may affect populations of marine invertebrates. Here we attempt to investigate a connection between invertebrate community structure and rockweed in Maine. Rockweed (Ascophyllum nodosum), a perennial species or no algal species present. brown macro-algae, creates complex structure Invertebrates will be identified and counted. and provide many essential ecological services to the intertidal ecosystem, including habitat for many ecologically and economically important species (Larsen 2012). As a primary producer, rockweed supports many secondary consumer populations. The 3-dimensional structure of rockweed canopy provides settlement, refuge, and foraging sites and significantly enhances diversity and abundance of invertebrate species (Schmidt et al. 2011). While some invertebrates graze upon rockweed, others receive protection against heat, sunlight, desiccation, and predation from it at low tide. Fig. 1. Invertebrates among rockweed Despite their ecological services, rockweed in Not only will the results of this study provide a has been commercially harvested for the better understanding of ecological significance production of alginates, fertilizers, and animal of rockweed-dominated areas to invertebrates feed. Because many species of intertidal as their habitat but will also help organizations to invertebrates use rockweed as their habitats, establish a better management plan and commercial harvesting potentially affects regulations regarding rockweed harvesting, in invertebrate diversity and abundance, which in order to minimize impacts to invertebrate turn could impact populations of fishes and habitat, as well as nursery and refuge for fishes, coastal birds that rely on these invertebrates as and foraging habitat for many bird species. their food source. Acknowledgements: Maine Costal Island The present study will assess the ecological National Wildlife Refuge, US