Variability in the tropical ocean-atmospheric system causes global scale climate anomalies, most evident in the El Niño-Southern Oscillation’s coupled climate feedbacks. Despite being an area of high interest, many questions still remain regarding the west Pacific warm pool’s response to external forcing, particularly its response to increases in anthropogenic greenhouse gases. Paleoclimate reconstructions coupled with model simulations provide insight into the tropical Pacific’s role in past climate variability necessary to the development of robust climate projections. Most paleoclimate records, however, still lack the resolution, length, and chronological control to resolve rapid variability against a background of orbital-scale variations. Here we present stalagmite oxygen isotope (δ18O) reconstructions from Gunung Mulu National Park (4oN, 115oE ), in northern Borneo, that provide reproducible centennial-scale records of western Pacific hydrologic variability that are precisely U/Th-dated and continuous throughout most of the late Pleistocene (0-160 thousand years ago, kybp). The record comprises an entire glacial-interglacial cycle, which allows us to investigate orbital-scale climate forcings and compare two well-dated glacial terminations in the western tropical Pacific. The ice- volume-corrected δ18O records suggest that glacial boundary condtions, which include significantly lower atmospheric carbon dioxide levels, did not drive significant changes in Mulu rainfall δ18O. Similarly, Borneo stalagmite δ18O is poorly correlated to either global sea level shifts or Sunda Shelf areal exposure is not evident. The Borneo record does vary in phase with local mid-fall equatorial insolation, suggesting that precessional forcing may impart a strong influence on hydroclimate variability in the warm pool. This is best illustrated across Glacial Termination II, when the oscillation of equatorial fall insolation is large and out of phase with ice sheet decay. We also use a subset of well-dated, high-resolution stalagmite δ18O records from Mulu to investigate millennial-scale climate variability during Marine Isotope Stages 3-5 (30-100kybp). We find that regional convection likely decreased during the six massive iceberg discharges defined in the North Atlantic sediment records (“Heinrich events”). The inferred drying (increased stalagmite δ18O) during Heinrich events is consistent with a southward shift of the Intertropical Convergence Zone – the dominant paradigm to explain global climate anomalies originating in the north Atlantic (ref). However, any hydrologic variability related to Dansgaad-Oeschgar (D/O) events, millennial-scale sawtooth temperature anomalies of the last glacial period first evident in the Greenland ice records, is notably absent in the stalagmite records. . The Mulu stalagmite record’s absence of D/O signal, however, is in marked contrast to the regional west Pacific marine records and suggests D/O events and Heinrich events may be characterized by fundamentally different climate mechanisms and feedbacks.

With continued warming regional surface air temperatures around the Artic in recent decades, there is growing importance in understanding how ice sheet dynamics interact with a shifting global climate system. This research investigates the spatial variability of sub-glacial hydrology under land terminating ice sheets in Western GrIS, when applying varying overburden ice pressures within Shreve’s (1972) hydraulic potential equation. The application of ArcGIS is used with adjusted k-values in the equation to route hydrological network systems under the ice sheet and help identify the processes taking place within the sub-glacial system. With focus on processes such as water piracy, we are able illustrate the effects that water at the base can have on ice sheet behaviors. i.e. velocity and mas balance. The findings conclude that the ice sheet is operating under conditions at its base with a k-value somewhere within the range of 0.9 to 1.1. This assumption is based on comparisons between modelled pro-glacial output with observed data taken from studies by Mikkelsen et al. (2014) and Smith et al. (2015), using input melt data at the surface (Lindback et. al., 2015). At this level of hydraulic potential, water piracy is effectively changing the course pathways of the hydrological network and therefore manipulating the size and shape of the sub-glacial catchments. As a result, discharge may leave the glacier from a different location than what would be assumed. Identifying the location and volume of water under particular ice sheets, compared to neighboring ice sheets, can be used to explain spatial and temporal differences in ice sheet characteristics. Such research is important in understanding both environmental and socio-economic implications at local to global scale. Although the application of GIS methodology is extremely useful is producing such results, it must be recognised that a high level of uncertainty and error exists in the data results. / Temperatur kan ha en särskilt stark inverkan på hur istäcken (glaciärer) beter sig. Även om det är väl känt att temperaturerna ökar både globalt och runt Arktis så har vi bara börjat förstå vikten av effekten av detta på glaciärer. Med ökande temperaturer har vi börjat se att en ökad avsmältning och en ökad mängd smältvatten i glaciala system kan ändra sättet en ismassa beter sig. Ett exempel på en sådan förändring är en ökad hastighet som ismassan rör sig i eftersom vatten fungerar som ett glidmedel mellan glaciären och den underliggande marken. Var vattnet finns under isen påverkar var istäcket rör sig. Man tror att en ökning i hastighet vid vissa delar av istäcket kan ledda till att det tunnas ut. Med tiden lämnar en allt större mängd vatten systemet vilket bidrar till mindre, retirerande glaciärer och en höjning av den globala havsytenivån då vattnet via vattendrag till slut rinner ut i havet. I den här studien användes ett kartläggningsprogram, Geografiskt Informationssystem (GIS), för att förutsäga var flodsystem under isen befinner sig. Detta kartläggningsprogram används eftersom dessa regioner inte är tillgängliga för observationer i fält. Tjockleken på istäcket som ligger ovanpå flodsystemet utövar ett tryck på vattnet och gör att det kan flöda emot gravitationen och i riktningar och med hastigheter som inte är typiska för flodsystem i varmare klimat. Denna process kallas vattenavlänkning. I denna studie används en ekvation i GIS för att variera trycket från det ovanliggande istäcket. Genom att ändra detta ändras hur stor vattenavlänkningen blir och därför även vilken väg vattnet tar under isen. Denna teknik tillåter oss att se vilken väg vattnet tar från att det kommer in i systemet vid toppen av istäcket till var det lämnar systemet genom vattendrag nedströms. Genom att veta var vattnet befinner sig kan man utröna varför isen rör sig annorlunda gentemot omkringliggande istäcken, och därför också dess påverkan på omgivande miljö såväl som sociala konsekvenser. Även om detta är en väldigt användbar metod för att kartlägga kanalsystem så finns det osäkerheter, till exempel i hur resultatet stämmer överens med verkliga scenarion. Så även om detta är användbart för att förstå teorin bakom processerna så är resultatet kanske inte helt tillförlitligt.

Prior to the passage of the 1976 Resource Conservation and Recovery Act (RCRA) 1.6 million bare steel Underground Storage Tanks (UST) were in use in the United States. Many of them were leaking. In Indiana approximately 13,000 UST remain but have been upgraded to meet current industry and regulatory standards. Cleaning up the petroleum releases from leaking UST has continued since it became evident that bare steel underground tanks leaked. In Northwest Indiana glacial moraine and outwash deposits from the Wisconsin Ice Age that retreated 10,000 years ago left 200 feet of glacial till above the underlying bedrock. Soil Vapor Extraction (SVE) and Air Sparging (AS) have proven to be effective and provide significant cost savings for remediation in the glacial deposits in Northwest Indiana. Indiana also has the Excess Liability Trust Fund (ELTF) to help pay for and to expedite clean-up of releases from registered UST. Cleaning up petroleum releases requires the appropriate technology for the localized geology, adequate funding, and appropriate guidance from state and federal regulations. This study discusses these issues at three sites in Northwest Indiana to demonstrate how technology, funding, and regulatory compliance must collaborate to work in the field.

No description available.

No description available.

The aims of this thesis are to refine the tephrochronology of the Öræfi district, SE Iceland and assess the Holocene glacier fluctuations of the Öræfajökull ice cap. The pattern and timing of glacier fluctuations are determined using glacial geomorphology and tephrochronology, and the implications for palaeoclimate are assessed. Iceland is important to the study of global and regional climatic change because it is located close to both the marine and atmospheric Polar Fronts widely regarded as the key factors in the climate of the North Atlantic region. Six outlet glaciers were studied: Svinafellsjökull, Virkisjökull, Kotárjökull and Kviárjökull originating from the Öræfajökull ice cap and Skaftafellsjökull and Morsárjökull originating from the Vatnajökull ice cap. A long history of glacier fluctuations were found with a similar temporal pattern of glacier oscillation between the outlets of Vatnajökull and Öræfajökull. A maximum of eight advances have been identified. The oldest advance is inferred to date from the maximum of the last Glaciation ca. 18000 yrs BP. The first advance in the Holocene occurred ca. 9700 BP during a still-stand of the last Termination. The onset of the Neoglaciation occurred between 6000 BP and 4600 BP with an expansion of all of the studied glaciers. Subsequent smaller advances have been dated to ca. 3200 BP, ca. 1800 BP, ca. 700 BP, ca. 200 BP and ca. 80 BP. The most significant movement of the Polar front during the Holocene is likely to have occurred around 5000 BP, and, as a consequence, an estimated temperature cooling of ca. 2.5°C took place in Iceland, perhaps the greatest cooling since the last Termination. Within the broad pattern of change, glaciers in the study area show variability which represents local precipitation patterns, contrasting topography and change in glacier process. In this thesis a total of 22 silicic tephra layers are identified from over 90 profiles in the study area. The majority of these layers are dated to the latter part of the Holocene. Three silicic tephras were deposited during historical time (post 900 AD) namely, Vö ca. 900AD,HI104 and Ö1362. The Vö ca. 900 AD and the H1104 tephras are located for the first time. Specific prehistoric (pre 900 AD) tephras identified include Hekla-Ö, Hekla-4 and Hekla-S. The tephrochronology of the Öræfi district is also used to assess the eruption history of the Öræfajökull stratovolcano during the Holocene. Prehistoric eruptions are dated to ca. 9200 BP, ca. 6500 BP(?), ca. 4700 BP, ca. 2800 BP and ca. 1500 BP. Jökulhlaups accompanied the eruptions of 1727 AD, 1362 AD and ca. 1500 BP and are likely to have followed older eruptions of the volcano. A strong relationship occurs between volcanic activity of the Öræfajökull stratovolcano and the pattern of glacier fluctuations. This is explained as a response to isostatic crustal adjustment during ice cap growth and decay, and indicates a general relationship between volcanic activity and climate change.

Biological diversity is controlled by an array of factors and processes all active at different spatial and temporal scales. Regional factors control what species are available to occur locally, whereas the local factors determine what species are actually capable of colonizing the locality. I have investigated how these local and regional factors affect species richness and diversity, mainly of fish in Swedish lakes and in order to assess the impact of dispersal mode one study on bacteria was also performed. In addition, potential first steps towards speciation were investigated in perch (Perca fluviatilis) from two different habitats. Fish species richness and diversity were found to be regulated by history, dispersal limitation and the local environment. In addition, striking similarities were found in the control of community composition for fish and bacteria. Both were regulated by nearly equal parts regional and local factors. The study of morphological and genetical variation in perch (Perca fluviatilis) revealed genetic differentiation at small spatial scales, suggesting that genetic differences can evolve between groups at strikingly small spatial scales, which might have implications for speciation in a long time perspective. Based on these findings I conclude that space and time matter. Space has the potential to isolate sites. And both dispersal and local extinctions, it seems, might take a long time, as effects of the last ice-age can still be seen on the contemporary fish community richness and composition.

The objective of this research is to interpret high-resolution palaeo-proxy data sets to understand the Asian summer monsoon variability in the past. This was done by synthesizing published palaeo-records from the Asian monsoon region, model simulation comparisons, and analysing new lake sedimentary records from northeast Thailand. Palaeo-records and climate modeling indicate a strengthened summer monsoon over Mainland Southeast Asia during the Last Glacial Maximum (LGM), compared to dry conditions in other parts of the Asian monsoon region. This can be explained by the LGM sea level low stand, which exposed Sundaland and created a large land-sea thermal contrast. Sea level rise ~19 600 years before present (BP), reorganized the atmospheric circulation in the Pacific Ocean and weakened the summer monsoon between 20 000 and 19 000 years BP. Both the Mainland Southeast Asia and the East Asian monsoon hydroclimatic records point to an earlier Holocene onset of strengthened summer monsoon, compared to the Indian Ocean monsoon. The asynchronous evolution of the summer monsoon and a time lag of 1500 years between the East Asian and the Indian Ocean monsoon can be explained by the palaeogeography of Mainland Southeast Asia, which acted as a land bridge for the movement of the Intertropical Convergence Zone. The palaeo-proxy records from Lake Kumphawapi compare well to the other data sets and suggest a strengthened summer monsoon between 10 000 and 7000 years BP and a weakening of the summer monsoon thereafter. The data from Lake Pa Kho provides a picture of summer monsoon variability over 2000 years. A strengthened summer monsoon prevailed between BC 170-AD 370, AD 800-960 and since AD 1450, and was weaker about AD 370-800 and AD 1300-1450. The movement of the mean position of the Intertropical Convergence Zone explains shifts in summer monsoon intensity, but weakening of the summer monsoon between 960 and 1450 AD could be affected by changes in the Walker circulation. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript..</p>

There is little consensus on what forced the climate of southern Africa to change during the Last Glacial Maximum (LGM). Because of southern Africa's latitudinal position, changes in seasonal precipitation can help resolve the influence of internal climate factors such as groundwater and external climate forcers such as large scale atmospheric circulation patterns. This paper presents a simple model of groundwater discharge based on permeability and topography in comparison with general circulation model precipitation results and paleoenvironmental proxy records. Results show that during the LGM the Intertropical Convergence Zone (ITCZ) likely weakened and moved slightly further south while the westerlies likely expanded slightly northward, with no significant change in strength. The climate and groundwater results were compared to the distribution of LGM and pre-LGM archaeological sites. Results show that the Later Stone Age peoples of southern Africa were likely inhabiting a relatively wet environment rather than an arid one.

There is little consensus on what forced the climate of southern Africa to change during the Last Glacial Maximum (LGM). Because of southern Africa's latitudinal position, changes in seasonal precipitation can help resolve the influence of internal climate factors such as groundwater and external climate forcers such as large scale atmospheric circulation patterns. This paper presents a simple model of groundwater discharge based on permeability and topography in comparison with general circulation model precipitation results and paleoenvironmental proxy records. Results show that during the LGM the Intertropical Convergence Zone (ITCZ) likely weakened and moved slightly further south while the westerlies likely expanded slightly northward, with no significant change in strength. The climate and groundwater results were compared to the distribution of LGM and pre-LGM archaeological sites. Results show that the Later Stone Age peoples of southern Africa were likely inhabiting a relatively wet environment rather than an arid one.