Caissie, Beth

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Landforms and Geology - Iowa's Nature Series

2021-05 , Moore, Peter , Caissie, Beth , Natural Resource Ecology and Management , Geological and Atmospheric Sciences , Extension and Outreach

From ocean-front property to spruce forest to today's rich organic prairie soils, Iowa's geological past is a fascinating story that can be told through careful inspection of the land beneath our feet. This article explores the long-view history of Iowa's landscapes and explains how the hills and valleys we call home were formed over millennia. To learn more about Iowa's Landforms and Geology, download the supplement article WL 17K - Geological Places to Visit. The Iowa’s Nature series was a collaborative project between Iowa State University Extension and Outreach, the Iowa Association of Naturalists, and the Iowa Department of Natural Resources with support from the Resource Enhancement and Protection Program. To learn more about the project, visit

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Oceanographic and Climatic Change in the Bering Sea, Last Glacial Maximum to Holocene

2018-01-01 , Pelto, Ben , Caissie, Beth , Caissie, Beth , Petsch, Steven , Brigham-Grette, Julie , Geological and Atmospheric Sciences

Post‐glacial sea level rise led to a direct connection between the Arctic and Pacific Oceans via the Bering Strait. Consequently, the Bering Sea experienced changes in connectivity, size, and sediment sources that were among the most drastic of any ocean basin in the past 30,000 years. However, the sedimentary response to the interplay between climate change and sea level rise in high‐latitude settings such as Beringia remains poorly resolved. To ascertain changes in sediment delivery, productivity, and regional oceanography from the Last Glacial Maximum (LGM) to the Holocene, we analyzed sedimentological, geochemical, and isotopic characteristics of three sediment cores from the Bering Sea. Interpretations of productivity, terrestrial input, nutrient utilization, and circulation are based on organic carbon isotopes (δ13Corg), total organic carbon (TOC), bulk nitrogen isotopes, total organic nitrogen, carbon/nitrogen ratios, elemental X‐ray fluorescence data, grain size, and presence of laminated or dysoxic, green intervals. Principal component analysis of these data captures key climatic intervals. The LGM was characterized by low productivity across the region. In the Bering Sea, deglaciation began around 18–17 ka, with increasing terrestrial sediment and TOC input. Marine productivity increased during the Bølling‐Allerød when laminated sediments revealed dysoxic bottom waters where denitrification was extreme. The Younger Dryas manifested increased terrestrial input and decreased productivity, in contrast with the Pre‐Boreal, when productivity markedly rebounded. The Pre‐Boreal and Bølling‐Allerød were similarly productive, but changes in the source of TOC and a δ13Corg depletion suggest the influence of a gradually flooding Bering Shelf during the Pre‐Boreal and Holocene.

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Sea surface temperature across the Subarctic North Pacific and marginal seas through the past 20,000 years: A paleoceanographic synthesis

2020-10-15 , Davis, Catherine , Caissie, Beth , Myhre, Sarah , Deutsch, Curtis , Caissie, Beth , Praetorius, Summer , Borreggine, Marisa , Thunell, Robert , Geological and Atmospheric Sciences

Deglacial sea surface conditions in the subarctic North Pacific and marginal seas are the subject of increasing interest in paleoceanography. However, a cohesive picture of near-surface oceanography from which to compare inter and intra-regional variability through the last deglaciation is lacking. We present a synthesis of sea surface temperature covering the open North Pacific and its marginal seas, spanning the past 20 ka using proxy records from foraminiferal calcite (δ18O and Mg/Ca) and coccolithophore alkenones (Uk’37). Sea surface temperature proxies tend to be in agreement through the Holocene, though Uk’37 records are often interpreted as warmer than adjacent δ18O or Mg/Ca records during the Last Glacial Maximum and early deglaciation. In the Sea of Okhotsk, Holocene discrepancies between δ18O and Uk’37 may be the result of changes in near-surface stratification. We find that sea-surface warming occurred prior to the onset of the Bølling-Allerød (14.7 ka) and coincident with the onset of the Holocene (11.7 ka) in much of the North Pacific and Bering Sea. Proxy records also show a cold reversal roughly synchronous with the Younger Dryas (12.9–11.7 ka). After the onset of the Holocene, the influence of an intensified warm Kuroshio Current is evident at higher latitudes in the Western Pacific, and an east-west seesaw in sea surface temperature, likely driven by changes in the strength of the North Pacific Gyre, characterizes the open interglacial North Pacific.

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Measuring the Effectiveness of Team-Based Learning Outcomes in a Human Factors Course

2016-12-20 , Bickelhaupt, Sarah , Dorius, Cassandra , Bestler, Laura , Gahn, Sandra , Jacobs, Keri , Smiley-Oyen, Ann , Artz, Georgeanne , Dorneich, Michael , Bender, Holly , Lamm, Monica , Rongerude, Jane , Stone, Richard , Caissie, Beth , Orgler, Lisa , Industrial and Manufacturing Systems Engineering

This paper will describe a synopsis of the development and application of a survey instrument to assess team skills and professional development outcomes of Team-Based Learning (TBL) in a human factors course. TBL is an advancing teaching pedagogy that shifts instruction from a traditional lecture-based teaching paradigm to a structured learning sequence that includes individual student preparation outside of class followed by active, in-class problem solving exercises completed by student learning teams. As an evolving teaching method, TBL appears to be producing new empirical learning outcomes in areas that have only preliminarily been explored. Traditionally, the effectiveness of TBL has been assessed through grades and numeric measures of performance; however, TBL was designed to both enhance learning as well as team collaboration and critical thinking skills. Thus there a need for a validated measurement instrument emerged to assess the development of team skills in TBL classes. The newly developed survey instrument is designed to assess three overarching factors within the TBL framework: 1) attitudes and beliefs about learning; 2) motivation to learn; and 3) professional development. A pilot survey was created and administered in the summer of 2013 to 25 undergraduate students at a large Mid-Western university and was tested for internal consistency. To further improve the quality of the survey, two focus groups were also conducted. In the fall of 2013 the revised survey was administered to 182 undergraduate students and in the spring of 2014 to 197 undergraduate students. Based on encouraging results, the survey was used to assess the learning outcome gains in a graduate level human factors course. Preliminary results for this sample showed modest gains in critical thinking and external motivation. The survey has the potential to provide instructors a mechanism to measure student learning gains in TBL educational settings.

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Sediment controls dynamic behavior of a Cordilleran Ice Stream at the Last Glacial Maximum

2020-04-14 , Cowan, Ellen , Caissie, Beth , Zellers, Sarah , Müller, Juliane , Walczak, Maureen , Worthington, Lindsay , Caissie, Beth , Clary, Wesley , Jaeger, John , Gulick, Sean , Pratt, Jacob , Mix, Alan , Fallon, Stewart , Geological and Atmospheric Sciences

The uncertain response of marine terminating outlet glaciers to climate change at time scales beyond short-term observation limits models of future sea level rise. At temperate tidewater margins, abundant subglacial meltwater forms morainal banks (marine shoals) or ice-contact deltas that reduce water depth, stabilizing grounding lines and slowing or reversing glacial retreat. Here we present a radiocarbon-dated record from Integrated Ocean Drilling Program (IODP) Site U1421 that tracks the terminus of the largest Alaskan Cordilleran Ice Sheet outlet glacier during Last Glacial Maximum climate transitions. Sedimentation rates, ice-rafted debris, and microfossil and biogeochemical proxies, show repeated abrupt collapses and slow advances typical of the tidewater glacier cycle observed in modern systems. When global sea level rise exceeded the local rate of bank building, the cycle of readvances stopped leading to irreversible retreat. These results support theory that suggests sediment dynamics can control tidewater terminus position on an open shelf under temperate conditions delaying climate-driven retreat.

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Bering Sea surface water conditions during Marine Isotope Stages 12 to 10 at Navarin Canyon (IODP Site U1345)

2016-09-01 , Caissie, Beth , Brigham-Grette, Julie , Caissie, Beth , Cook, Mea , Colmenero-Hidalgo, Elena , Geological and Atmospheric Sciences

Records of past warm periods are essential for understanding interglacial climate system dynamics. Marine Isotope Stage 11 occurred from 425 to 394 ka, when global ice volume was the lowest, sea level was the highest, and terrestrial temperatures were the warmest of the last 500 kyr. Because of its extreme character, this interval has been considered an analog for the next century of climate change. The Bering Sea is ideally situated to record how opening or closing of the Pacific–Arctic Ocean gateway (Bering Strait) impacted primary productivity, sea ice, and sediment transport in the past; however, little is known about this region prior to 125 ka. IODP Expedition 323 to the Bering Sea offered the unparalleled opportunity to look in detail at time periods older than had been previously retrieved using gravity and piston cores. Here we present a multi-proxy record for Marine Isotope Stages 12 to 10 from Site U1345, located near the continental shelf-slope break. MIS 11 is bracketed by highly productive laminated intervals that may have been triggered by flooding of the Beringian shelf. Although sea ice is reduced during the early MIS 11 laminations, it remains present at the site throughout both glacials and MIS 11. High summer insolation is associated with higher productivity but colder sea surface temperatures, which implies that productivity was likely driven by increased upwelling. Multiple examples of Pacific–Atlantic teleconnections are presented including laminations deposited at the end of MIS 11 in synchrony with millennial-scale expansions in sea ice in the Bering Sea and stadial events seen in the North Atlantic. When global eustatic sea level was at its peak, a series of anomalous conditions are seen at U1345. We examine whether this is evidence for a reversal of Bering Strait throughflow, an advance of Beringian tidewater glaciers, or a turbidite.