Master of Arts (MA), Bowling Green State University, 1949, History

Committee: R. Stanley McCordock (Advisor) Subjects: History

Doctor of Philosophy, The Ohio State University, 2020, Geodetic Science

Quantitative assessment of the mass balance of polar ice sheets plays an important role in better understanding the response of ice sheets to anthropogenic climate change, the present-day and future global sea level change, and interactions between the ice sheets and the atmosphere, ocean and the solid Earth. In this study, I investigate the mass balance of Greenland and Antarctica ice sheets using Gravity Recovery And Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) twin-satellite missions gravity data from April 2002 to August 2020. Auxiliary gravity data from the Swarm mission 3-satellite constellation are also used to support the analysis bridging the GRACE/GRACE-FO data gap (July 2017 to May 2018). Ensemble models are composed combining the official GRACE temporal gravity solutions from CSR, GFZ, JPL and the in-house developed GRACE models using the improved energy balance approach (EBA). The improved atmospheric de-aliasing data produced using the ECMWF (European Centre for Medium-Range Weather Forecasts) Reanalysis 5th Generation (ERA5) data product, and 3-dimensional atmosphere mass computational algorithms are collectively used. The Swarm gravity models are also ensemble of four solutions produced from the kinematic orbit data using four different gravity recovery methods. Post-processing of the gravity models includes replacing low degree spherical harmonic terms (geocenter motions, J2 and J3), destriping filtering, Gaussian smoothing, glacial isostatic adjustment (GIA), forward modeling based signal leakage reduction and ellipsoidal correction. The satellite gravimetric data show that during the period of 2002/04-2020/08, Greenland and Antarctica ice sheets experience rapid mass losses at mean rates of -235.6±3.8 Gt/yr and -122.6±4.6 Gt/yr respectively, equivalent to 0.65 mm/yr and 0.34 mm/yr global sea level changes. In spatial domain, the southern part (including southeast and southwest regions) of Greenland contributes 52.3% of the total Green (open full item for complete abstract)

Committee: C.K. Shum (Advisor); Michael Bevis (Committee Member); Howat Ian (Committee Member); Wei Feng (Committee Member) Subjects: Climate Change; Earth; Geophysics

Doctor of Philosophy, The Ohio State University, 2020, Earth Sciences

The Greenland Ice Sheet (GrIS) is losing mass at accelerated rates in the 21st century, due in part to faster flow at large outlet glaciers. Chapter 2 presents work published in The Cryosphere (King et al., 2018). Here, we sample rapid changes in thickness and velocity at all large outlet glaciers to derive the first continuous, GrIS-wide record of total ice sheet discharge, or the volume of ice glaciers export, for the 2000-2016 period. We resolve a distinct pattern of seasonal variability with an amplitude of 6%, and analyze how seasonal to annual variability in the discharge time series relates to both meltwater runoff and glacier front position changes over the same period. We find that the annual magnitude of discharge is closely related to cumulative front position change (r2 = 0.79), averaging over 2 km of retreat since 2000. We find that larger seasonal quantities of runoff do not relate to increased annual discharge, although seasonal acceleration of ice discharge does closely coincide with the onset of the melt season. These results suggest that changes in glacier front position drive secular trends in discharge, whereas the impact of runoff is likely limited to the summer months when observed seasonal variations are substantially controlled by the timing of meltwater input. In Chapter 3, we extend our 2000-2016 discharge time series to the period 1985-2018, combining more than three decades of GrIS-wide observational products of outlet glacier velocity, elevation, and front position changes, and compare decadal variability in discharge with calving front position. We find that the close relationship between frontal change and ice discharge identified over the 2000-2016 record holds true for the 34-year record, and that increased glacier discharge can be attributed almost entirely to the retreat of glacier fronts, rather than inland ice sheet processes, such as changes in meltwater runoff. Discharge sensitivity to retreat is remarkably consistent across (open full item for complete abstract)

Committee: Ian Howat (Advisor); Lonnie Thompson (Committee Member); Michael Durand (Committee Member); Bryan Mark (Committee Member) Subjects: Climate Change; Earth; Environmental Studies; Geological; Geophysical; Geophysics

MARCH, University of Cincinnati, 2019, Design, Architecture, Art and Planning: Architecture

The arctic is no longer out of reach of man kind. Through an analysis of the land, people, and future, the opportunity for prospective development in the arctic is evident. In recent years, all eyes have begun to shift northward, not only in aspects of environmental consciousness, but also in aspects of political dominance and resource attainment. As the sea ice is beginning to retreat closer to the north pole, the arctic waters are becoming more navigable, opening the door for the Northern Sea Route shipping lanes and dissolving the natural boundary that once prevented the extraction industry from tapping the wealth that laid dormant beneath. For the purpose of this thesis, the moral, political, and ecological questions of oil and gas extraction in the arctic will not be answered. Instead, this thesis will resolve the future problem of housing within small arctic towns, as the extraction industry will begin to draw thousands of people into the most remote reaches on earth. Hammerfest, Norway, was among the first arctic villages to give birth to the oil and gas industry, and saw a temporary population increase of 3,500 construction workers virtually overnight, as they arrived from all over the world to construct a liquid natural gas processing plant in 2005. Following the completion of the processing plant, the town then transitioned from 3,500 temporary workers to 2,000 new permanent residents which filled the employment opportunities provided by the processing plant. This increased growth was successfully absorbed by Hammerfest, which had a population of 8,000 before the emergence of the extraction industry. However, the same will not hold true for Upernavik, Greenland, a barren island with a population of only 1000, and who's western shoreline was just opened to the oil and gas extraction industry. This thesis will develop a system for Upernavik to withstand the same growth that Hammerfest experienced, by proposing a new housing typology which capitalizes on the (open full item for complete abstract)

Committee: Michael McInturf M.Arch. (Committee Chair); Aarati Kanekar Ph.D. (Committee Member) Subjects: Architecture

Master of Science, The Ohio State University, 2019, Earth Sciences

The margins of the greenland ice sheet are the leading contribution to global sea level rise, and changes have been noted at many of its marine terminating outlet glaciers. Here we present changes in the rates of surface elevation change along the entire margin of the Greenland ice sheet at 205 marine terminating glaciers between 1978 and 2015. We analyzed an assemblage of multiple surface elevation data sets to assess how rates of surface elevation change are changing at these glaciers. We find that the change in rates of surface elevation loss have increased by 150% to 300% since pre-2000 rates into the 2000's, following by a 10% to 20% slowdown in current times. We find that these modern rates are significantly different from historic rates, suggesting that current forcings are changing the ice loss mechanics of the GrIS in the 21st century.

Committee: Ian Howat Ph.D (Advisor); Michael Durand Ph.D (Committee Member); C.K. Shum Ph.D (Committee Member) Subjects: Climate Change; Earth

Master of Science, The Ohio State University, 2018, Environmental Science

Refractory black carbon (rBC) particles are naturally and anthropogenically emitted as a by-product of the incomplete combustion of carbonaceous materials. As a strong absorber of incoming solar radiation, rBC warms whichever part of the atmosphere in which the particle is suspended and decreases the albedo of any ice- or snow-covered surface onto which it has been deposited. This makes the Arctic particularly vulnerable to rBC deposition, as atmospheric pollutants concentrate there and deposited rBC will accelerate glacier melt and make the immediate area more susceptible to warming. Within the past 15 years, global attention has turned to targeting rBC emissions in mitigation strategies in an attempt to slow the rate of near-term climate change, as rBC particles only have an atmospheric residence time of 7-10 days, which provides mitigation efforts with more immediate results. This research utilizes a firn core collected from Crawford Point (CP), Greenland in the summer of 2007 by the Program for Arctic Regional Climate Assessment (PARCA) to quantify and characterize the deposition of rBC and other absorbing materials, such as dissolved organic matter (DOM), onto the Greenland ice sheet (GrIS) from 1980-2007. Median rBC concentration throughout the CP firn core is 0.86 g/L and ranges from 0.02-19.93 µg/L. The declining trends observed in anthropogenic rBC emissions and deposition to CP suggest that the implemented mitigation efforts may be successful. However, Canadian forest fires can lead to high deposition events at CP, which will only get worse as climate change impacts continue to worsen. This research also aims to determine emission and source of rBC particles in three circumpolar countries – the Russian Federation, Canada, and the United States of America – and one regional economic integration organization – the European Union – and their mitigation efforts to decrease air pollution as it relates to rBC. The two largest sources of anthropogenic rBC emis (open full item for complete abstract)

Committee: Joel Barker (Advisor); Cinnamon Carlarne (Committee Member); Ellen Mosley-Thompson (Committee Member) Subjects: Environmental Science

Doctor of Philosophy, The Ohio State University, 1969, Graduate School

Committee: Not Provided (Other) Subjects: Geology

Master of Science, The Ohio State University, 2016, Geological Sciences

Supraglacial lakes have been expanding into the interior of the Greenland ice sheet under a warming climate. In recent years lakes have been forming in unprecedented regions beyond the ablation zone. The expansion of lakes well into the lower accumulation zone of the ice sheet suggests a change in the condition of the firn towards promoting meltwater runoff as opposed to infiltration and storage. We explore the relationship between lake formation and firn structure in this comparative study of two lakes in western Greenland. From remote sensing observations and regional climate model meteorological output of the two lakes over a brief period (2009-2015), we find lakes form over near-surface ice lens within the firn and the development of percolation lakes is dependent upon ice dynamics.

Committee: Ian Howat (Advisor); Doug Alsdorf (Committee Member); Bryan Mark (Committee Member) Subjects: Earth; Geology; Hydrology; Remote Sensing

Doctor of Philosophy, The Ohio State University, 2015, Geodetic Science and Surveying

The flow velocity of glacier and its fluctuation are valuable data to study the contribution of sea level rise of ice sheet by understanding its dynamic structure. Repeat-image feature tracking (RIFT) is a platform-independent, feature tracking-based velocity measurement methodology effective for building a time series of velocity maps from optical images. However, limited availability of perfectly-conditioned images motivated to improve robustness of the algorithm. With this background, we developed an improved RIFT algorithm based on multiple-image multiple-chip algorithm presented in Ahn and Howat (2011). The test results affirm improvement in the new RIFT algorithm in avoiding outlier, and the analysis of the multiple matching results clarified that each individual matching results worked in complementary manner to deduce the correct displacements. LANDSAT 8 is a new satellite in LANDSAT program that has begun its operation since 2013. The improved radiometric performance of OLI aboard the satellite is expected to enable better velocity mapping results than ETM+ aboard LANDSAT 7. However, it was not yet well studied that in what cases the new will sensor will be beneficial, and how much the improvement will be obtained. We carried out a simulation-based comparison between ETM+ and OLI and confirmed OLI outperforms ETM+ especially in low contrast conditions, especially in polar night, translucent cloud covers, and bright upglacier with less texture. We have identified a rift on ice shelf of Pine island glacier located in western Antarctic ice sheet. Unlike the previous events, the evolution of the current started from the center of the ice shelf. In order to analyze this unique event, we utilized the improved RIFT algorithm to its OLI images to retrieve time series of velocity maps. We discovered from the analyses that the part of ice shelf below the rift is changing its speed, and shifting of splashing crevasses on shear margin is migrating to the center o (open full item for complete abstract)

Committee: Ian Howat Dr. (Advisor); Alper Yilmaz Dr. (Committee Member); Michael Durand Dr. (Committee Member) Subjects: Climate Change; Earth; Geography; Remote Sensing

MS, University of Cincinnati, 2012, Arts and Sciences: Geology

This study reports a reconstruction of Holocene lacustrine paleotemperatures and paleovegetation for the Scoresby Sund region 70.5¿¿¿¿ north latitude in east Greenland using long- chain alkenones and n-alkanes. Long-chain alkenones (LCAs) are biomarkers, which are produced by haptophyte algae that can provide information on regional paleoclimate conditions. C37 LCAs were analyzed using the alkenone unsaturation index, Uk37, along with published lacustrine alkenone temperature calibrations. LCAs were identified in only 1 lake (Snoopy Lake) out of 4 lakes that were examined within Scoresby Sund. At Snoopy Lake, the coldest temperature of the Holocene was measured at 9,700 YBP while the warmest temperature was measured at 7,300 YBP, corresponding with the mid-Holocene climate optimum. Late Holocene warming indicated by the Snoopy Lake Uk37 record is inconsistent with other temperature records from Greenland. We suspect this difference in Uk37 predicted temperatures is related to extrinsic factors that modify the haptophyte Uk37 proxy rather than warmer than expected absolute temperatures in eastern Greenland. Terrestrial leaf wax lipids, n-alkanes, were also analyzed in order to infer changes in vegetation caused by changes in climate. Increasing concentration of long-chain n-alkane values indicate rapid expansion of terrestrial plants 8,000 years before present, followed by decreasing abundance towards present. This vegetation pattern is consistent with other regional records of the Holocene Thermal Maximum and the Little Ice Age. The similarities between our temperature reconstruction for the Early Holocene and other records suggest that something fundamental changed during the latter part of the Holocene effecting the alkenone unsaturation. Future work needs to characterize extrinsic factors that modify Uk37 proxies and methods to identify when reconstructed temperatures are biased.

Committee: Thomas Lowell PhD (Committee Chair); Aaron Diefendorf PhD (Committee Member); Warren Huff PhD (Committee Member) Subjects: Geology

MS, University of Cincinnati, 2011, Arts and Sciences: Geology

The Polar Regions are sensitive to climate change and the large ice masses located there can impact the global earth system via linkages such as sea level. Presented here is a study of a small, isolated ice mass that may be more sensitive than the Greenland Ice Sheet. Thus, here a study of the Istorvet Ice Cap is presented including a geomorphic map, radiocarbon dates from lake sediment cores as well as in-situ plant remains, and a mass balance model. Radiocarbon dates from lake sediments located in lowest elevation basin suggest this region had become deglaciated by at least 6671 yr BC (7840±80 14C yr BP: OS-86718). Additional radiocarbon dates from the same lakes shows at least a low elevation portion of the ice cap was highly restrictive relative to present for most of the Holocene. The youngest age from four similarly aged samples suggest the onset of the LIA began sometime after 737 AD (1270±80 14C yr BP: OS-86725). A mass balance model based on the PDD method suggests the average ELA over a 21-year period is 854 m a.s.l. Estimates of cumulative ice mass suggest up to 70 m of ice mass loss over the same time period. Therefore we would conclude that the Ice Cap is in a dire state. Lastly, radiocarbon dates from terrestrial in-situ plant remains from an spatial and altitudinal range suggest the Istorvet Ice Cap does not respond to the same temperature forcing as the Greenland Ice Sheet. Also, evidence is presented that suggests the Istorvet Ice Cap was expanding during the Medieval Warm Period and does not fit the traditional classification of the Little Ice Age.

Committee: Thomas Lowell PhD (Committee Chair); David Byer Nash PhD (Committee Member); Lewis Owen PhD (Committee Member) Subjects: Geology

Master of Arts, The Ohio State University, 2012, Geography

Snow and ice mass balance is an important concept to describe the growth or decay of land ice. Mass balance is measured as the difference between the amount of accumulation and the amount of ablation. In that this value could provide the significant information on the sea level rise and the global warming trend, many researchers have been trying to estimate or predict the input to the mass balance from net snow accumulation rates. However, predicting accumulation is not simple because this value varies with time and place. In this study, spatial and temporal characteristics are thus investigated to provide basic information on accumulation. The result represents that the ice cores in central-west and south-east basins are the most influential in total average accumulation over Greenland because of their large magnitude of accumulation. However, when the accumulation data are normalized, other sites (Tunu-N, ACT-04-2, and ACT-04-3) also appear to be important for total ice sheet accumulation. 5-year triangular filter has been adapted to find the correlations between ice cores. Central basins represent the large improvement and the northwest, northeast and southwest basins represent low improvement. The trend of increased signal to noise ratio may be related to the latitude. The correlations between most ice cores decay with distance. Especially, central-east and central-west basins show the strong distance-decay patterns. South east basin also represents relatively high distance decays. Otherwise, north and southwest basins do not represent high distance decay trend consistently. While southwest and southeast basins are located in almost same latitude, these two basins represent different trend regarding correlation and slope. This might be related to the prevailing easterly winds, frequent cyclogenesis, and orographic enhancement. High amount of accumulation in southeast basin might be also related. Over the whole period, temporal autocorrelation was not foun (open full item for complete abstract)

Committee: Jason Box (Advisor); Jialin Lin (Committee Member); Desheng Liu (Committee Member) Subjects: Climate Change

Master of Arts, The Ohio State University, 2012, Geography

With global sea level rising and Arctic temperatures increasing more rapidly than any other location on the globe, it is important to understand how surface melting in Greenland today compares with that in the past. A melt history (1765 – 2006 C.E.) has been reconstructed from an ice core collected in 2007 at Crawford Point (69.9°N; 47.0°W, 2022 masl) in west central Greenland. This site lies in the zone of intermittent summer melt and percolation which may result in formation of melt features, thus potentially providing a record of surface warmth. Melt features are primarily bubble free and thus appear clearer and brighter than the surrounding snow, firn, or ice. This paper presents an efficient and relatively inexpensive technique for quantifying the annual melt percent from an ice core. The Crawford Point core was photographed and high-resolution digital images were used to quantify the extent of melt in each year using a time scale previously constructed by counting seasonal variations in δ18O, complemented by seasonal variations in the concentrations on dust, nitrate, and sulfate. Melt percent was determined using a 1x1 cm grid which was overlain on each year within the core. Regression analysis was used to determine that melt within the Crawford Point ice core has been increasing at a rate of 0.08% per year, since 1765, and has increased to 0.11% per year after 1900. This record was compared to contemporaneous observations including other melt histories, the existing satellite record, meteorological observations, patterns of atmospheric circulation, other ice core-derived proxy records, and volcanic activity. Regression relationships were employed to examine the correlations between melt at Crawford Point and these other variables. While melt preserved in ice cores has been previously assessed, there has been no sustained methodology to facilitate comparisons among the resulting records. The results of this study establish the need for standardization of the (open full item for complete abstract)

Committee: Ellen Mosley-Thompson PhD (Advisor); Bryan Mark PhD (Committee Member); Berry Lyons PhD (Committee Member); Lonnie Thompson PhD (Committee Member) Subjects:

Master of Science, The Ohio State University, 2011, Geological Sciences

Outlet glaciers and ice caps on the periphery of the Greenland Ice Sheet have been observed to be extremely sensitive to climate. The limited studies conducted on the marine-terminating glaciers of eastern Greenland's Geikie Plateau and Blosseville Coast suggest exceptionally rapid rates of mass loss and short-term variability in ice dynamics. This study is targeted at a region of central east Greenland for which GRACE mass-anomaly observations show substantial recent mass-loss since its launch in March 2002. Additionally, glaciers in this region terminate into Denmark Straight, which is a thermodynamic transition zone between the Arctic and North Atlantic oceans. Extensive glacial change has been more pronounced through the Denmark Straight and south of the straight, which supports the hypothesis that ocean dynamics, specifically the Irminger Current and East Greenland Current, are supporting increased melt at the ice-ocean interface. It is possible that an appreciable amount of melt and ice loss south of Kangerdlugssuaq is occurring as a result of warmer subpolar water flowing into glacial fjords. We present changes to 38 marine-terminating glaciers as observed using Landsat-7 ETM+ imagery to develop a time series of changing front positions and flow speeds of these glaciers from 2000 to 2010. ASTER DEMs were used to quantify elevation change and thinning. Additionally, we examine sea surface temperatures at five sites along the east Greenland coast to identify possible correlations between warming of the sea surface and increased melt at the glacier termini.

Committee: Ian Howat PhD (Advisor); Bryan Mark PhD (Committee Member); Carolyn Merry PhD (Committee Member) Subjects: Earth; Geophysical; Remote Sensing

Doctor of Philosophy, The Ohio State University, 2010, Geological Sciences

Continuous monitoring of changes in the Greenland ice sheet from both space and air borne sensors has been conducted since the early 1970's. Since the mid-1990's dramatic changes occurring on the Greenland ice sheet have been observed both from space borne sensors and field work. These changes, primarily mass loss from the ice sheet, are related to the observed trend of earth's warmer climate in recent decades both in peer reviewed journals and in popular media. This dissertation addresses two parameters that contribute to Greenland ice sheet mass balance estimates. The first factor is characterization of surface melting of the Greenland ice sheet from satellite-based passive and active microwave sensors. We use a wavelet based edge detection technique to delineate surface melt from brightness temperature measured by passive microwave sensors. Along with brightness temperature data, we also use normalized backscatter data from the Quick Scatterometer (QuikSCAT) as an independent sensor for comparison with the radiometer derived results. We use a semi-empirical threshold based method for surface melt detection from QuikSCAT. Our results show a step-like, consistent increase in melt area of the Greenland ice sheet since 1995. This step-like increase is also observed in the mean summer air temperature along portions of the Greenland coast. The 1995 step-like increase of melt area (and melt index, a measure of melt intensity) is correlated with a distinct change of the North Atlantic Oscillation (NAO) index (from positive to negative) after 1995. The second factor is mass accumulation in the upper reaches of the ice-sheet. We use an empirical model that correlates mean annual brightness temperature to annual accumulation rate. We apply a microwave emission model for the dry snow region of Greenland to show that 37 GHz vertically polarized brightness temperature data are better suited to capture the inter-annual variability of snow accumulation. Using our model we esti (open full item for complete abstract)

Committee: Kenneth Jezek (Advisor); Joel Johnson (Committee Member); Ralph von Frese (Committee Member) Subjects: Geophysics

Master of Science, The Ohio State University, 2010, Geological Sciences

Significant changes in the dynamics of Greenland's marine-terminating outlet glaciers within the past few years indicate a rapid and complex response of these systems to recent climatic forcing. Widespread and substantial accelerations in flow-speed of outlet glaciers in southeast Greenland have been linked to destabilization and retreat of glacier fronts triggered by thinning to flotation induced by warmer ocean temperatures. There is concern that ongoing coastal thinning in western Greenland will trigger a similar response, further threatening the stability of the ice sheet. Despite regional ice thinning and retreat, the glaciers of Greenland's northwest coast have not yet undergone substantial acceleration. This suggests a lessened dynamic sensitivity of these glaciers to changes at the ice front than southeastern glaciers, likely due to differences in glacier geometry. To investigate the potential controls behind this contrasting behavior, we derive time series' of front position, surface elevation, and surface thinning for 59 marine-terminating outlet glaciers in west Greenland from 2000-2009. Surface speeds are derived for several glaciers to determine sensitivity to large front retreats in this region. Using these data, we look for patterns in the relationships between retreat, thinning, acceleration, and geometric variables, such as surface slope, to determine the first-order controls on glacier sensitivity. Data are compared to regional changes in air and ocean temperatures to assess similarities in climate forcing conditions along Greenland's west coast. We conclude there is no direct relationship between front retreat and measured geometric parameters applicable to the entire study region. The relative importance of surface slope as a control of glacier behavior is highly variable and must be coupled to bathymetric data in order to understand and accurately model outlet glacier response to climate forcing.

Committee: Ian Howat PhD (Advisor); Lonnie Thompson PhD (Committee Member); William Lyons PhD (Committee Member) Subjects:

Doctor of Philosophy, The Ohio State University, 2009, Atmospheric Sciences

The Odden event is a dominant mode of the Arctic sea ice variability, which is very important for the Arctic climate. The Odden sea ice feature extends northeastward from the Arctic pack ice of the east Greenland Sea during winter and spring, typically covering an area between 8°W and 5°E, and between 73° and 77°N. The key causes and forcing of Odden sea ice variability in the atmosphere and ocean is examined using the Community Sea Ice Model5.0 (CSIM5) within a Slab Ocean Model (SOM) called the M configuration of Community Climate System Model3.0 (CCSM3) provided by the National Center for Atmospheric Research (NCAR). A 26 year control run is made with the T62 NCEP/NCAR Reanalysis (NNR) atmospheric data from 1979 – 2004, and the simulated northern Atlantic sea ice is compared with that from the Hadley Center Sea ice and Sea Surface Temperature (HadISST) observational dataset in order to evaluate the model's capabilities. The control run sea ice data were subjected to a rotated principal component analysis (RPCA) that revealed a component (#3) mode of variability that exhibited Odden-like variability similar to that obtained in observational data. To further investigate the single or multiple effects from the atmospheric and oceanic parameters associating with the Odden sea ice, 18 experiments are conducted with the NNR and a 1° x 1° Simple Ocean Data Assimilation (SODA) for the atmospheric and oceanic forcing, respectively. In one set of experiments the atmosphere and ocean model are run simultaneously in efforts to simulate the Odden while other experiments evaluate Odden forcing of individual atmospheric parameters with other parameter forcing being held in a non-Odden state. Model forcing data for Odden ice conditions are from 1997 (January – December) while those from 1994 are used as the forcing for non-Odden conditions, in keeping with observational studies. Results show that the model sea ice concentration (SIC) and ice thickness exhibit large variability i (open full item for complete abstract)

Committee: Jeffery C. Rogers PhD (Advisor); Jialin Lin PhD (Committee Member); David H. Bromwich PhD (Committee Member) Subjects: Earth; Environmental Science; Geography

Master of Science, The Ohio State University, 2009, Atmospheric Sciences

Supra-glacial melt lakes form in the Greenland ice sheet ablation region in response to surface melt. The Jakobshavn Ablation Region (JAR) in west – central Greenland (68.2 – 68.8°N) is an area with a high areal concentration of melt lakes, providing an ideal region to study melt lake development. Moderate Resolution Imaging Spectroradiometer (MODIS) imagery are acquired for the 2000 – 2008 melt seasons (days 150 – 274) to observe the spatial and temporal melt lake characteristics. Knowing that melt rates vary with elevation, JAR is divided into five elevation zones of 250 m intervals, between 585 – 1835 m above sea level. An empirically-derived depth function, based on MODIS optical reflectance, is applied to classified melt lake pixels at JAR, yielding depth, area and volume statistics. There is a strong correlation between melt lake area and volume quantities, regardless of elevation. Peak zonal fractional melt area, volume maxima and peak mean melt lake depth are reached at the mid-ablation zone (1035 – 1334 m). Melt intensity is determined from a Positive Degree Day (PDD) model. A correlation is found between melt lake area and volume anomalies and PDD anomalies that decrease with elevation. The melt season at the uppermost elevation (1585 – 1834 m) begins five weeks after the onset at the lowest elevation (585 – 834 m). The date of maximum area and volume also increase with time, with a difference of 50 - 60 days. Average melt season at JAR lasts 70 – 85 days below 1584 m and decreases to 30 days at the uppermost zone (1585 – 1834 m). To verify MODIS-derived lake area accuracy, three IKONOS 1 m resolution images are compared for a single lake, Lake Disco (67.23°N, 48.61°W). Uncertainty in MODIS estimates of area are 20±2%. Such differences confirm the difficulty of identifying depth values between 0 and ~2.5 m from the Box and Ski (2007) lake depth-retrieval classification. Shallow depths prevent the MODIS sensor's coarse resolution from identifying lake per (open full item for complete abstract)

Committee: Jason Box (Advisor); Ian Howat (Committee Member); Bryan Mark (Committee Member) Subjects: Earth; Geography; Remote Sensing

Doctor of Philosophy, The Ohio State University, 2008, Atmospheric Sciences

The Greenland Ice Sheet provides an excellent archive for the paleoclimatic and paleoenvironmental conditions, particularly for the Northern Hemisphere. The chemical analyses of five multi-century Greenland ice cores have yielded a high resolution volcanic aerosol history. This provides an improved estimate of the stratospheric sulfate burden, which is an important input for models assessing the climatic impacts of volcanic eruptions. Additionally, these cores made it possible to confirm the timing of the arrival of the ash and aerosols from Laki over Greenland, which is essential for dating ice cores from low accumulation region in Greenland.The spatial characteristics of the sulfate aerosol deposition associated with specific eruptions provide information about the transport processes and the mechanisms dominating local deposition. Examination of the sulfate deposited from the 1783-84 A.D. Laki and the 1815 A.D. Tambora eruptions reveals that precipitation over the southeastern regions in 1783 may have been suppressed. This also suggests that Laki aerosols were likely deposited primarily by dry deposition. In contrast, the Tambora sulfate is more spatially homogeneous, suggesting deposition primarily via wet processes. To quantify the impact of geographical factors on the deposition of volcanic sulfate over Greenland, a category explanatory variable analysis was conducted. The results indicate that the location of ice cores relative to the ice divide strongly affects EXS deposition, but the elevation of the core site is relatively unimportant. Since 1850, the EXS flux extracted from Greenland ice cores has increased primarily due to anthropogenic sulfur emissions. To quantify this impact as well as the accumulation effect, a linear mixed model was applied. The results indicate that for every Gg increase in the annual NH sulfur emissions, there is a 0.0013% increase in the annual non-volcanic sulfate flux. The impact of accumulation on sulfate deposition varies ove (open full item for complete abstract)

Committee: Ellen Mosley-Thompson PhD (Advisor); Lonnie Thompson PhD (Committee Member); Catherine Calder PhD (Committee Member); Bryan Mark PhD (Committee Member) Subjects: Atmosphere

Doctor of Philosophy, The Ohio State University, 2004, Atmospheric Sciences

Climatic information available from the spatially extensive suite of firn and ice cores collected under the Program for Arctic and Regional Climate Assessment (PARCA), in conjunction with other data, provides an unparalleled opportunity to investigate accumulation changes over the Greenland ice sheet and to assess its ability to record and preserve a history of North Atlantic climate variability. The ice core derived accumulation histories demonstrate that the influence of glaciological noise on the climate signal is strongly influenced by the accumulation rate. Thus, it may be difficult to discern regionally representative climate signals from individual cores at lower accumulation sites on short time scales suggesting that either time or spatial averaging of the records is necessary. Individual rotated principal components analysis (RPCA) on the time series of net annual accumulation, the total concentration of insoluble dust particles, and the δ18O annual average and seasonal extrema reveal that cores located in different regions of the ice sheet do not vary consistently for the period of record in this study (1965-1996). Specifically, cores from southern Greenland vary in a manner different from those in the central west region. Thus, proxy climate histories drawn from a single core record are not necessarily representative of the entire ice sheet. Comparison of the scores associated with the central west and southern Greenland spatial patterns with atmospheric and oceanic data suggest that different processes may be responsible for delivery of precipitation to each region. Correlations of the North Atlantic Oscillation with the core data, combined with composites of mean sea level pressure and 500 hPA heights for accumulation extremes, suggest a negative relationship with the central west region during winter, spring, and summer. Conversely, the same analyses for the southern region suggest a positive relationship to the NAO during summer. Accumulation in the c (open full item for complete abstract)

Committee: Ellen Mosley-Thompson (Advisor) Subjects: Physics, Atmospheric Science