Glacier response to North Atlantic climate variability during the Holocene

Small glaciers and ice caps respond rapidly to climate variations, and records of their past extent provide information on the natural envelope of past climate variability. Millennial-scale trends in Holocene glacier size are well documented and correspond with changes in Northern Hemisphere summer insolation. However, there is only sparse and fragmentary evidence for higher-frequency variations in glacier size because in many Northern Hemisphere regions glacier advances of the past few hundred years were the most extensive and destroyed the geomorphic evidence of ice growth and retreat during the past several thousand years. Thus, most glacier records have been of limited use for investigating centennial-scale climate forcing and feedback mechanisms. Here we report a continuous record of glacier activity for the last 9.5 ka from southeast Greenland derived from high-resolution measurements on a proglacial lake sediment sequence. Physical and geochemical parameters show that the glaciers responded to previously documented Northern Hemisphere climatic excursions, including the \u278.2 ka\u27 cooling event, the Holocene Thermal Maximum, Neoglacial cooling, and 20th century warming. In addition, the sediments indicate centennial-scale oscillations in glacier size during the late Holocene. Beginning at 4.1 ka, a series of abrupt glacier advances occurred, each lasting similar to 100 years and followed by a period of retreat, that were superimposed on a gradual trend toward larger glacier size. Thus, while declining summer insolation caused long-term cooling and glacier expansion during the late Holocene, climate system dynamics resulted in repeated episodes of glacier expansion and retreat on multi-decadal to centennial timescales. These episodes coincided with ice rafting events in the North Atlantic Ocean and periods of regional ice cap expansion, which confirms their regional significance and indicates that considerable glacier activity on these timescales is a normal feature of the cryosphere. The data provide a longer-term perspective on the rate of 20th century glacier retreat and indicate that recent anthropogenic-driven warming has already impacted the regional cryosphere in a manner outside the natural range of Holocene variability

Particle Movement and Separation Phenomena for a Gravity Separator: I. Development of a Markov Probability Model and Estimation of Model Parameters

The complexity of gravity separator mechanics precludes the use of a deterministic model for particle movement on a gravity separator. Particle movement is examined as a stochastic process; a distance-transition Markov probability model for particle movement is proposed. A linear programming method for estimation of the Markov model parameters is explained

Mapping sediment–landform assemblages to constrain lacustrine sedimentation in a glacier-fed lake catchment in northwest Spitsbergen

Changes in the deposition of fine-grained rock-flour in glacier-fed lakes reflect glacier variability. This meltwater-driven signal is, however, often overprinted by other processes. To constrain the signature of lacustrine sedimentation, we mapped the catchment of glacier-fed Lake Hajeren in northwest Spitsbergen, identifying sediment sources and linking them to surface processes. To this end, we employed a combined approach of aerial image interpretation and field mapping. Our map comprises sediment–landform assemblages commonly found in pro-, peri- and paraglacial landsystems on Spitsbergen, including weathered moraines outboard Little Ice Age limits. Based on the presented map, we argue that mass-wasting does not directly impact lake sedimentation. Also, due to the scarcity of fines in historical glacial deposits, we suggest that modified glacigenic sediments only briefly affect a recorded glacier signal, following retreat. These findings highlight the value of geomorphological maps as tools to constrain catchment processes, improving the interpretation of lake sediment records.publishedVersio

Effect of Humidity Ratio on Corn Moisture Content as Determined by the Air-Oven

Shelled com was oven dried at 103° C for 72 h with air having dew point temperatures of 9, 13, 18, 24, and 29° C. An additional test was performed with desiccant-dried air. Measured values of air-oven corn moisture content (superficial corn moisture content) dropped by as much as 0.9 percentage points (dry basis) as a result of increases in humidity ratio of the drying air. The amount of moisture left in the corn samples at the conclusion of the 72-h drying period, the apparent final moisture content, was found to be a quadratic function of humidity ratio

Competency-Based Assessment of Engineering Technology Program Outcomes

ABET is the preeminent organization in the U.S. for accreditation of 2- and 4-yr college-level educational programs in applied science, computing, engineering, and technology. ABET accreditation regimes require program outcomes assessment. The Technology Accreditation Commission (TAC) of ABET is charged with accrediting two- and four-yr Engineering Technology (ET) programs. The 4-year ET major at the University of Delaware is a general ET program; and, for the purposes of TAC of ABET accreditation, must demonstrate its graduates have mastered the a through k program outcomes listed in TAC of ABET documentation for Criterion 3 of its General Criteria for Accrediting Engineering Technology Programs. The a through k program outcomes, which include such statements as: a. an appropriate mastery of the knowledge, techniques, skills and modern tools of their disciplines, and b. an ability to apply creativity in the design of systems, components or processes appropriate to program objectives, are notoriously difficult to assess because they require complex blends of interdependent skills, the evaluations of which may be influenced by considerable subjectivity. Iowa State University (ISU) 3 has adopted a competency-based assessment approach to demonstrate program outcomes for Engineering Accreditation Commission (EAC) of ABET 2 accreditation of all its engineering programs in addition to its programs in agricultural systems technology and industrial technology. The ISU technology programs are accredited by the Association of Technology, Management, and Applied Engineering 4 . In consultation with graduates and industry partners, ISU developed a set of 14 “workplace competencies.” Each competency was designed to be “clear, concise and independent of all others” 3 . Each competency is demonstrated by a “set of observable and measurable key actions.” The confounding that plagues assessment of the ABET a-k program outcomes is avoided, and a measure of objectivity is introduced. The ISU competencies were determined to be “necessary and sufficient to address the EAC of ABET a-k outcomes” 3 , and a matrix mapping the ISU workplace competencies to the EAC of ABET a-k outcomes was developed. This paper describes the adaptation of ISU’s competency-based assessment approach for outcomes assessment and TAC of ABET accreditation of the University of Delaware’s ET program. University of Delaware student competencies, derived from the ISU student competencies, are mapped to the TAC of ABET a-k program outcomes. As with ISU’s approach, a student ePortfolio system is utilized. Evaluations of competencies are informed by the student’s performance in a “Discovery Learning Experience”—either a technical practicum in industry or an undergraduate research project

Particle Movement and Separation Phenomena for a Gravity Separator: II. Experimental Data and Performance of Distance-Transition Markov Models

Linear programming procedures are used to fit stationary and nonstationary distance-transition Markov probability models to experimentally obtained particle distribution data from the deck of a gravity separator. Particle movement modeled is that of a light discard fraction. Performance of the models is examined by comparing predicted typical\u27\u27 particle pathways with observed particle pathways. The Markov process is found to be an appropriate model of particle movement

Sedimentary DNA and Molecular Evidence for Early Human Occupation of the Faroe Islands

The Faroe Islands, a North Atlantic archipelago between Norway and Iceland, were settled by Viking explorers in the mid-9th century CE. However, several indirect lines of evidence suggest earlier occupation of the Faroes by people from the British Isles. Here, we present sedimentary ancient DNA and molecular fecal biomarker evidence from a lake sediment core proximal to a prominent archaeological site in the Faroe Islands to establish the earliest date for the arrival of people in the watershed. Our results reveal an increase in fecal biomarker concentrations and the first appearance of sheep DNA at 500 CE (95% confidence interval 370-610 CE), pre-dating Norse settlements by 300 years. Sedimentary plant DNA indicates an increase in grasses and the disappearance of woody plants, likely due to livestock grazing. This provides unequivocal evidence for human arrival and livestock disturbance in the Faroe Islands centuries before Viking settlement in the 9th century

Sedimentary DNA and molecular evidence for early human occupation of the Faroe Islands

The Faroe Islands, a North Atlantic archipelago between Norway and Iceland, were settled by Viking explorers in the mid-9th century CE. However, several indirect lines of evidence suggest earlier occupation of the Faroes by people from the British Isles. Here, we present sedimentary ancient DNA and molecular fecal biomarker evidence from a lake sediment core proximal to a prominent archaeological site in the Faroe Islands to establish the earliest date for the arrival of people in the watershed. Our results reveal an increase in fecal biomarker concentrations and the first appearance of sheep DNA at 500 CE (95% confidence interval 370-610 CE), pre-dating Norse settlements by 300 years. Sedimentary plant DNA indicates an increase in grasses and the disappearance of woody plants, likely due to livestock grazing. This provides unequivocal evidence for human arrival and livestock disturbance in the Faroe Islands centuries before Viking settlement in the 9th century

Using the surface profiles of modern ice masses to inform palaeo-glacier reconstructions

Morphometric study of modern ice masses is useful because many reconstructions of glaciers traditionally draw on their shape for guidance Here we analyse data derived from the surface profiles of 200 modern ice masses-valley glaciers icefields ice caps and ice sheets with length scales from 10(0) to 10(3) km-from different parts of the world Four profile attributes are investigated relief span and two parameters C* and C that result from using Nye s (1952) theoretical parabola as a profile descriptor C* and C respectively measure each profile s aspect ratio and steepness and are found to decrease in size and variability with span This dependence quantifies the competing influences of unconstrained spreading behaviour of ice flow and bed topography on the profile shape of ice masses which becomes more parabolic as span Increases (with C* and C tending to low values of 2 5-3 3 m(1/2)) The same data reveal coherent minimum bounds in C* and C for modern ice masses that we develop into two new methods of palaeo glacier reconstruction In the first method glacial limits are known from moraines and the bounds are used to constrain the lowest palaeo ice surface consistent with modern profiles We give an example of applying this method over a three-dimensional glacial landscape in Kamchatka In the second method we test the plausibility of existing reconstructions by comparing their C* and C against the modern minimum bounds Of the 86 published palaeo ice masses that we put to this test 88% are found to be plausible The search for other morphometric constraints will help us formalise glacier reconstructions and reduce their uncertainty and subjectiveness (C) 2010 Elsevier Ltd All rights reserve