Summer Rupper

                     
Assistant Professor
Office, S317 ESC
(801) 422-6946
Paleoclimate Laboratory, S378 ESC
Glaciology Laboratory, C180 ESC
summer_rupper@byu.edu

Only by understanding the natural climate system of Earth can we hope to unravel the intricacies of anthropogenic changes superimposed on that system.  My current research projects are part of this larger effort to characterize the natural climate variability – with a particular emphasis on glaciers as recorders and indicators of climate.  On-going projects include analysis of stable isotopes from high alpine ice cores, reconstructions of past climate using ice core chemistry and snow accumulation data, reconciling geomorphic evidence of past glacier extents with climate, and quantifying glacier sensitivity to climate change.


Projects

Below is a list of the major projects my research group is currently focused on. If you would like to hear about these or other projects we are involved in, please feel free to contact me.

1. Annual Satellite Era Accumulation Patterns over the West Antarctic Ice Sheet Divide: A study using shallow ice cores, near-surface radars and satellites

Funding: NSF-OPP/ANT 0944730 and 1348459 (REU), 08/2010-/82014
Collaborators: Lora Koenig (NASA-Goddard), Rick Forster (Univ. of Utah)


Mapping the spatial and temporal variations in accumulation rates over the Antarctic ice sheet is essential for understanding ice sheet responses to climate forcing. This project will broaden knowledge of annual accumulation patterns over the West Antarctic Ice Sheet by processing existing near-surface radar data taken on the US ITASE traverse in 2000 and by gathering and validating new ultra/super-high-frequency (UHF) radar images of near surface layers (to depths of ~15 m), expanding abilities to monitor recent annual accumulation patterns from point-source ice cores to radar lines. Shallow (15 m) ice cores will be collected in conjunction with UHF radar images to confirm that radar echoed returns correspond with annual layers, and/or sub-annual density changes in the near-surface snow, as determined from ice core chemistry and stable isotopes. This project will additionally improve accumulation monitoring from space-borne instruments by comparing the spatial-radar-derived-annual accumulation time series to the passive microwave time series dating back over 3 decades and covering most of Antarctica.

                

Figures from Burgener et al., 2013; Photo courtesy of Clement Miege

2.  Climate and Glacier Change in Bhutan: the last millennia, present and future

Funding: NSF-EAR 1256551 and 1304351,  08/2012-08/2016
Collaborators: Joerg Schaefer and Ed Cook (LDEO of Columbia Univ.), Karma Tsering (DHMS in Bhutan)


Environmental Change in the Himalayas impacts societies in the most densely populated area on earth. Rapid glacier retreat, affecting river discharge and, in turn, energy production and agriculture and jeopardizing societies by Glacial Lake Outburst Floods (GLOFs), is a particularly worrisome example. It is the primary goal of this proposal to provide robust information about past, present and future glacier and climate change in the monsoonal Himalayas, and in turn to contribute to a more robust scientific platform for decision makers and mitigation strategists. Our target area are the mountains in the Kingdom of Bhutan, south-eastern monsoonal Himalayas. Bhutan’s welfare is linked to glacier dynamics because hydropower generation, the primary source of income, and agricultural irrigation, are fueled by glacier melt. Melting glaciers and the steep relief have made GLOFs a prime hazard for the societies of Bhutan and their Himalayan neighbors and the hazard potential in space and time critically depends on current and future glacier melt. We have indentified outstanding climate records: (i) well-preserved and -resolved moraine sequences, the target of a mapping and dating experiments; (ii)
Conifer tree species that will allow us to reconstruct climate, especially summer temperature, back through the last millennium; (iii) Glaciers that are particularly sensitive to changes in temperature as compared to precipitation, making them excellent targets for more refined glaciological modeling, and linking the tree-ring temperatures to the glacier reconstructions.

                

Figures from Rupper et al., 2012; Photos courtesy of Mike Roberts and Karma Tsering

3.  Lake Level Changes in Response to Interannual Climate Variability

Collaborators: Kat Huybers and Gerard Roe (Univ. of Washington)

Among climate proxies, lakes are of particular importance, as they directly reflect a balance between evaporation and precipitation. However, lakes, like other geophysical systems, integrate interannual climate fluctuations to produce persistent fluctuations on timescales of decades or longer. This inertia makes it difficult to distinguish changes in response to stochastic climate forcing from true shifts in climate. Further, the size and shape of a lake determines a unique temporal and spatial response to a forcing. This project focuses on the development of a versatile lake-level model based on mass conservation and lake-reservoir geometry, from which one can determine the dynamic response of a lake. We apply this model, initially, to the Great Salt Lake as a test case. We will then apply this model to other closed-basin lake systems. The end goal is a cohesive and methodical investigation of lake-level changes and their causes in order to understand lakes’ response to climate variability.


Figures courtesy of Kat Huybers

4. Controls on Meltwater Variability in the Arid Tropics: Implications for the role of glaciers in landsape evolution

Funding: NSF-EAR GLD, Pending

Collaborators: Gordon Bromley (Univ. of Maine), Gisela Winckler (LDEO of Columbia Univ.), Noah Finnegan (Univ. of California – Santa Cruz)


The proposed research will investigate the role of glacial meltwater in landscape evolution in arid tropical environments. Relict glacio-fluvial landforms on glacierized peaks in the Western Cordillera, southern Peruvian Andes, attest to repeated high-magnitude fluctuations in meltwater discharge. These deposits form the basis for assessing the relative influences of glacial and climatic factors on meltwater production, and thus fluvial sedimentation, in this arid region. The overarching research objectives are to understand how, why, and when glaciers in the arid tropics transition between a melt-dominated regime, capable of significant geomorphic change, and a dry, sublimation-dominated state (such as exists today) effectively disconnected from landscape processes. This information is crucial for assessing the importance of glaciers as geomorphic agents in tropical highlands. To address these goals, we will map and date fluvial landforms associated with past periods of enhanced glacial discharge in the Western Cordillera and will model the factors controlling meltwater generation. Specifically, we will (i) establish the extent and age of relict outwash features, (ii) use those data to quantify respective meltwater fluxes, and (iii) model climatic-glaciologic conditions required to generate such discharge and to drive long-term meltwater variability.

                

Figures and images courtesy of Gordon Bromley; Middle figure from Bromely et al., 2011