Posts Tagged «ice sheets»

This investigation’s major goal is to develop and use models constrained by satellite and ground observations to study the controls on fast ice stream flow.

Deeply embayed ice shelves and narrower fringing ice shelves surround much of Antarctica. Recent results indicate that these ice shelves help regulate the flow of upstream glaciers and ice streams (“ice-shelf buttressing”). This investigation focuses on determining the mass balance of Antarctica’s non-Peninsula ice shelves and on improving our knowledge of the processes that control basal melt.

Bell, R. E., M. Studinger, C. A. Shuman, M. A. Fahnestock, and I. Joughin,’ Large subglacial lakes in East Antarctica at the onset of fast-flowing ice streams’, Nature, 445, 904-907, 2007.

E. Ciracì, I. Velicogna and T. C. Sutterley. Mass Balance of Novaya Zemlya Archipelago, Russian High Arctic, Using Time-Variable Gravity from GRACE and Altimetry Data from ICESat and CryoSat-2. Remote Sensing, 10(11): 1817, 2018.

Conway, H., Smith, B., Vaswani, P. et al, “A low-frequency ice-penetrating radar system adapted for use from an airplane: test results from Bering and Malaspina Glaciers, Alaska, USA”, Annals Glaciology, 50(51), 93-97, 2009.

We are using field and remote sensing data to investigate Elevation Change Anomalies (ECAs) discovered recently in the Ross Sea sector of the West Antarctic Ice Sheet (WAIS), which reveal the filling and draining of subglacial lakes.

Fudge, T.J., and B. Smith, “Instruments and Methods Light propagation in firn: application to borehole video“, J. Glaciology, 56(198), 614-624, 2010.

Numerous recent studies have revealed rapid change in ice discharge from Greenland’s outlet glaciers. A near doubling in flow speed of many of Greenland’s glaciers substantially increased the rate at which the ice sheet calved icebergs to the ocean over the last five years.

This project characterizes the Greenland Ice Sheet’s subglacial microbial communities to investigate the effect of microbes on lithospheric weathering and nutrient fluxes from the GrIS margin in West Greenland.

Howat, I. M., I. Joughin, and T. A. Scambos,’ Rapid changes in ice discharge from Greenland outlet glaciers’, Science, 315, 1559-1561, 2007.

Howat, I.M., Smith, B.E., Joughin, I., et al, Rates of southeast Greenland ice volume loss from combined ICESat and ASTER observations, Geophys. Res. Lett., 35(17), L17505, 2008.

IceBridge is a NASA project that supports the acquisition of various data from aircraft in both polar regions that will bridge the gap in coverage between the now defunct ICESat satellite and the next generation ICESat II to be launched in 2015 at the earliest. The main focuses of the data acquisition will be laser altimetry and radar measurements of ice sheets (Greenland and Antarctica) and sea ice (Arctic and Antarctica).

PI: Ian Joughin The West Antarctic Ice Sheet is losing mass, in large part because of rapid thinning of the Amundsen Coast glaciers. Estimates of Amundsen Coast thinning range from 46 to 86 Gtons/yr, with the 40-Gton/yr difference in estimates being nearly equivalent to the combined outflow of Mercer, Whillans, Kamb, and Bindschadler ice streams (46 Gtons/yr). While warmer ocean temperatures may drive this thinning, the large uncertainties in the current mass balance estimates largely arise from poor knowledge of the snowfall accumulation over Pine Island, Thwaites, Smith, Pope and Kohler glaciers. This International Polar Year project is determining accumulation rates in this vastly under-sampled region to remove the large uncertainties in current mass balance estimates.

Joughin, I., ‘Climate change – Greenland rumbles louder as glaciers accelerate’, Science, 311, 1719-1720, 2006.

Joughin, I., I. Howat, M. Fahnestock, B. Smith, W. Krabill, R. Alley, H. Stern, and M. Truffer, 2008, Continued Evolution of Jakobshavn Isbrae Following its Rapid Speedup, J. Geophys. Res., 113, F04006, doi:10.1029/2008JF001023.

Joughin, I., S. Tulaczyk, J.L. Bamber, D. Blankenship, J.W. Holt, T. Scambos, and D.G. Vaughan,’ Basal conditions for Pine Island and Thwaites glaciers, West Antarctica, determined using satellite and airborne data’, J. Glaciol., 55, 245-257, 2009.

Junge, K., and B.D. Swanson,’ High-resolution ice nucleation spectra of sea-ice bacteria: Implications for cloud formation and life in frozen environments‘, Biogeosciences Discussion, 4, 4261-4282, 2008.

Krawczynski, M.J., M.D. Behn, S.B. Das, and I. Joughin,’ Constraints on the lake volume required for hydro-fracture through ice sheets’, Geophys. Res. Lett., 36, 10.1029/2008GL036765, 2009.

Laurence, G., Burgess, D., Copland, L., Langley, K., Gogineni, P., Paden, J., Leuschen, C., van As, D., Fausto, R., Joughin, I., Smith, B. (2019), Measuring Height Change Around the Periphery of the Greenland Ice Sheet With Radar Altimetry. Frontiers in Earth Science, 7:146. doi:10.3389/feart.2019.00146

This project will explore the relationship between deep-freeze bacterial activity, proteomics, polymers and the physical state of the ice and will provide important keys to questions regarding life under extreme conditions, be it in the various ice formations here on Earth, the atmosphere or elsewhere in the universe.

Mock, T. and K. Junge, “Psychrophilic Diatoms: Mechanisms for Survival in Freeze-thaw cycles”, Algae and Cyanobacteria in Extreme Environments, Springer Netherlands; DOI10.1007/978-1-4020-6112-7, pp. 343 to 364, 2007.

Shepherd, A., A. Hubbard, M. King, M. McMillan, and I. Joughin,’ Greenland ice sheet motion coupled with daily melting in late summer’, Geophys. Res. Lett., 36, 10.1029/2008GL035758, 2009.

Smith, B.E., Fricker, H.A., Joughin, I.R.., and S. Tulaczyk, ‘An inventory of active subglacial lakes in Antarctica detected by ICESat (2003-2008)’, J. Glaciology, 55(192), 573-595, 2009.

Smith, B.E., Raymond, C.F. and T. Scambos, “Anisotropic texture of ice sheet surfaces”, J. Geophys. Res., 111(F1), F01019, 2006.

T. C. Sutterley, T. Markus, T. Neumann, M. van den Broeke, J. M. van Wessem and S. Ligtenberg. Antarctic Ice Shelf Thickness Change from Multi-Mission Lidar Mapping. The Cryosphere, 2019.

T. C. Sutterley, I. Velicogna, X. Fettweis, E. Rignot, B. Noël and M. van den Broeke. Evaluation of reconstructions of snow/ice melt in Greenland by regional atmospheric climate models using laser altimetry data. Geophysical Research Letters, 45(16):8324–8333, 2018.

Ian Joughin serves as Deputy PI on the GSFC CryoDyn Earth Ventures 2 project. He is developing science and measurement objectives for the mission. He is also evaluating whether the mission and instrument are consistent with these objectives and provides expert advice to guide the mission planning and utilization of the data.

We are employing new remote sensing methods applied to multiple satellite data sets to measure the total discharge of ice from the grounded Antarctic Ice Sheet. This effort also will provide the most comprehensive mapping ever of the grounding line position, as well as ice thickness and velocity along and in the vicinity of the grounding line. These products are sensitive indicators of changes and will serve as benchmark data sets of the International Polar Year suitable for subsequent comparisons to identify and quantify future changes in the ice sheet.

Vogel, S. W., Tulaczyk, S., Kamb, B., Engelhardt, H., Carsey, F. D., Behar, A. E., Lane, A. L. & Joughin, I,’ Subglacial conditions during and after stoppage of an Antarctic Ice Stream: Is reactivation imminent?’, Geophysical Research Letters, 32, 2005.

Winebrenner, D.P., B. Smith, G. Catania, C.F. Raymond, and H. Conway,’ Estimation of the temperature-dependence of radio-frequency attenuation beneath Siple Dome, from wide-angle and profiling radar observations’, Ann. Glaciology, Vol. 37, 2003.