ALBERT

Description:    Calculations were performed with the Earth system model of intermediate complexity LOVECLIM to study the response of the Greenland and Antarctic ice sheets to sustained multi-millennial greenhouse warming. Use was made of fully dynamic 3D thermomechanical ice-sheet models bidirectionally coupled to an atmosphere and an ocean model. Two 3,000-year experiments were evaluated following forcing scenarios with atmospheric CO 2 concentration increased to two and four times the pre-industrial value, and held constant thereafter. In the high concentration scenario the model shows a sustained mean annual warming of up to 10°C in both polar regions. This leads to an almost complete disintegration of the Greenland ice sheet after 3,000 years, almost entirely caused by increased surface melting. Significant volume loss of the Antarctic ice sheet takes many centuries to initiate due to the thermal inertia of the Southern Ocean but is equivalent to more than 4 m of global sea-level rise by the end of simulation period. By that time, surface conditions along the East Antarctic ice sheet margin take on characteristics of the present-day Greenland ice sheet. West Antarctic ice shelves have thinned considerably from subshelf melting and grounding lines have retreated over distances of several 100 km, especially for the Ross ice shelf. In the low concentration scenario, corresponding to a local warming of 3–4°C, polar ice-sheet melting proceeds at a much lower rate. For the first 1,200 years, the Antarctic ice sheet is even slightly larger than today on account of increased accumulation rates but contributes positively to sea-level rise after that. The Greenland ice sheet loses mass at a rate equivalent to 35 cm of global sea level rise during the first 1,000 years increasing to 150 cm during the last 1,000 years. For both scenarios, ice loss from the Antarctic ice sheet is still accelerating after 3,000 years despite a constant greenhouse gas forcing after the first 70–140 years of the simulation. Content Type Journal Article Pages 1-20 DOI 10.1007/s10712-011-9131-5 Authors P. Huybrechts, Earth System Sciences and Departement Geografie, Vrije Universiteit Brussel, Brussels, Belgium H. Goelzer, Earth System Sciences and Departement Geografie, Vrije Universiteit Brussel, Brussels, Belgium I. Janssens, Earth System Sciences and Departement Geografie, Vrije Universiteit Brussel, Brussels, Belgium E. Driesschaert, Faculty of Sciences, Université Catholique de Louvain, Louvain-la-Neuve, Belgium T. Fichefet, Georges Lemaître Centre for Earth and Climate Research (TECLIM), Earth and Life Institute, Université Catholique de Louvain, Louvain-la-Neuve, Belgium H. Goosse, Georges Lemaître Centre for Earth and Climate Research (TECLIM), Earth and Life Institute, Université Catholique de Louvain, Louvain-la-Neuve, Belgium M.-F. Loutre, Georges Lemaître Centre for Earth and Climate Research (TECLIM), Earth and Life Institute, Université Catholique de Louvain, Louvain-la-Neuve, Belgium Journal Surveys in Geophysics Online ISSN 1573-0956 Print ISSN 0169-3298

Description:    Anthropogenic climate change has emerged as one of the major challenges for mankind in the centuries to come. The strongly modified composition of the atmosphere, due to emissions of greenhouse gases and aerosol particles, leads to an enhanced greenhouse effect and also intensified backscattering of solar radiation by aerosol particles. The resulting global mean warming will have a major impact on the entire cryosphere, with global consequences via mean sea level rise and redistributed precipitation. This introductory presentation will summarize the emergence of the topic, its already observed consequences for the cryosphere, and it will also discuss issues in climate policy making when dealing with the climate change challenge. Content Type Journal Article Pages 1-10 DOI 10.1007/s10712-011-9129-z Authors Hartmut Grassl, Max Planck Institute for Meteorology, Hamburg, Germany Journal Surveys in Geophysics Online ISSN 1573-0956 Print ISSN 0169-3298

Description:    Recent satellite observations of the Antarctic and Greenland ice sheets show accelerated ice flow and associated ice sheet thinning along coastal outlet glaciers in contact with the ocean. Both processes are the result of grounding line retreat due to melting at the grounding line (the grounding line is the contact of the ice sheet with the ocean, where it starts to float and forms an ice shelf or ice tongue). Such rapid ice loss is not yet included in large-scale ice sheet models used for IPCC projections, as most of the complex processes are poorly understood. Here we report on the state-of-the art of grounding line migration in marine ice sheets and address different ways in which grounding line migration can be attributed and represented in ice sheet models. Using one-dimensional ice flow models of the ice sheet/ice shelf system we carried out a number of sensitivity experiments with different spatial resolutions and stress approximations. These are verified with semi-analytical steady state solutions. Results show that, in large-scale finite-difference models, grounding line migration is dependent on the numerical treatment (e.g. staggered/non-staggered grid) and the level of physics involved (e.g. shallow-ice/shallow-shelf approximation). Content Type Journal Article Pages 1-19 DOI 10.1007/s10712-011-9133-3 Authors David Docquier, Laboratoire de Glaciologie, Université Libre de Bruxelles, CP160/03, Av. F.D. Roosevelt 50, 1050 Brussels, Belgium Laura Perichon, Laboratoire de Glaciologie, Université Libre de Bruxelles, CP160/03, Av. F.D. Roosevelt 50, 1050 Brussels, Belgium Frank Pattyn, Laboratoire de Glaciologie, Université Libre de Bruxelles, CP160/03, Av. F.D. Roosevelt 50, 1050 Brussels, Belgium Journal Surveys in Geophysics Online ISSN 1573-0956 Print ISSN 0169-3298

Description:    The monitoring of global lightning activity and its spatial and temporal variations is known to be very essential for the study of global warming, the subject of greatest concern to human beings on planet Earth today. As a method of remote sensing for the global lightning distribution, we have proposed an inverse problem by using the data of natural electromagnetic noise in the ELF (extremely low frequency) Schumann resonance (SR) band observed simultaneously at a few stations around the world. The fundamentals of this inversion problem (or ELF tomography) to the SR data have been presented and the first attempt to deduce the global lightning distribution by means of the real SR data has been performed, which has indicated a possibility of snapshots of well-known thunderstorm centers on the globe. This ELF tomography consists of two stages. The first stage is the inversion of the ELF field power spectra to the distribution of lightning intensity by distance relative to an observation point. The obtained distance profiles of intensity of sources at a few stations are used as tomographic projections for reconstructing a spatial distribution of sources in the second stage. Maps of the global lightning distributions constructed by the result of inversions of ELF background field spectra obtained from three stations around the world show that the most active regions vary meridionally on the diurnal time scale being connected mainly with continental areas in the tropics. We do hope that this kind of inversion method to multi-stationed ELF data will be of great importance in the future. Content Type Journal Article Pages 1-28 DOI 10.1007/s10712-011-9135-1 Authors Alexander Shvets, Usikov Institute of Radiophysics and Electronics, National Academy of Sciences of Ukraine, 12 Academician Proskura St., Kharkov, 61085 Ukraine Masashi Hayakawa, Advanced Wireless Communications Research Center, University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo, 182-8585 Japan Journal Surveys in Geophysics Online ISSN 1573-0956 Print ISSN 0169-3298

Description:    Recent dramatic acceleration, thinning and retreat of tidewater outlet glaciers in Greenland raises concern regarding their contribution to future sea-level rise. These dynamic changes seem to be parallel to oceanic and climatic warming but the linking mechanisms and forcings are poorly understood and, furthermore, large-scale ice sheet models are currently unable to realistically simulate such changes which provides a major limitation in our ability to predict dynamic mass losses. In this paper we apply a specifically designed numerical flowband model to Jakobshavn Isbrae (JIB), a major marine outlet glacier of the Greenland ice sheet, and we explore and discuss the basic concepts and emerging issues in our understanding and modelling ability of the dynamics of tidewater outlet glaciers. The modelling demonstrates that enhanced ocean melt is able to trigger the observed dynamic changes of JIB but it heavily relies on the feedback between calving and terminus retreat and therefore the loss of buttressing. Through the same feedback, other forcings such as reduced winter sea-ice duration can produce similar rapid retreat. This highlights the need for a robust representation of the calving process and for improvements in the understanding and implementation of forcings at the marine boundary in predictive ice sheet models. Furthermore, the modelling uncovers high sensitivity and rapid adjustment of marine outlet glaciers to perturbations at their marine boundary implying that care should be taken in interpreting or extrapolating such rapid dynamic changes as recently observed in Greenland. Content Type Journal Article Pages 1-22 DOI 10.1007/s10712-011-9132-4 Authors Andreas Vieli, Department of Geography, Durham University, Durham, DH1 3LE United Kingdom Faezeh M. Nick, Laboratoire de Glaciologie, Université Libre de Bruxelles, 1050 Bruxelles, Belgium Journal Surveys in Geophysics Online ISSN 1573-0956 Print ISSN 0169-3298

Description:    Recent observations of ocean temperature in several Greenland fjords suggest that ocean warming can cause large changes in the outlet glaciers in these fjords. We have observed the Helheim outlet-glacier front in the Sermilik Fjord over the last three decades using satellite images, and the vertical fjord temperature and salinity during three summer expeditions, 2008–2010. We show that the subsurface water below 250 m depth is the warm saline Atlantic Water from the Irminger Sea penetrating into the fjord and exposing the lower part of the Helheim glacier to warm water up to 4°C. Lagged correlation analysis spanning the 30-year time series, using the subsurface Atlantic Water temperature off the coast as a proxy for the variability of the subsurface warm Atlantic Water in the fjord, indicates that 24% of the Helheim ice-front movement can be accounted for by ocean temperature. A strong correlation (–0.75) between the ice-front position and the surface air temperature from a nearby meteorological station suggests that the higher air temperature causes melting and subsequent downward percolation of meltwater through crevasses leading to basal lubrication; the correlation accounts for 56% of the ice-front movement. The precise contribution of air temperature versus ocean temperature however, remains an open question, as more oceanographic and meteorological measurements are needed close to the glacier terminus. Content Type Journal Article Pages 1-10 DOI 10.1007/s10712-011-9130-6 Authors Ola M. Johannessen, Mohn Sverdrup Center for Global Ocean Research at Nansen Environmental and Remote Sensing Center, and Nansen Scientific Society, Thormøhlensgate 47, 5006 Bergen, Norway Alexander Korablev, Mohn Sverdrup Center for Global Ocean Research at Nansen Environmental and Remote Sensing Center, and Nansen Scientific Society, Thormøhlensgate 47, 5006 Bergen, Norway Victoria Miles, Mohn Sverdrup Center for Global Ocean Research at Nansen Environmental and Remote Sensing Center, and Nansen Scientific Society, Thormøhlensgate 47, 5006 Bergen, Norway Martin W. Miles, Uni Research—Bjerknes Centre for Climate Research, 5007 Bergen, Norway Knut E. Solberg, Fotspor.org, Oslo, Norway Journal Surveys in Geophysics Online ISSN 1573-0956 Print ISSN 0169-3298

Description:    Until quite recently, the mass balance (MB) of the great ice sheets of Greenland and Antarctica was poorly known and often treated as a residual in the budget of oceanic mass and sea level change. Recent developments in regional climate modelling and remote sensing, especially altimetry, gravimetry and InSAR feature tracking, have enabled us to specifically resolve the ice sheet mass balance components at a near-annual timescale. The results reveal significant mass losses for both ice sheets, caused by the acceleration of marine-terminating glaciers in southeast, west and northwest Greenland and coastal West Antarctica, and increased run-off in Greenland. At the same time, the data show that interannual variability is very significant, masking the underlying trends. Content Type Journal Article Pages 1-11 DOI 10.1007/s10712-011-9137-z Authors Michiel R. Van den Broeke, Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, The Netherlands Jonathan Bamber, Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, Bristol, UK Jan Lenaerts, Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, The Netherlands Eric Rignot, Department of Earth System Science, University of California, Irvine, CA, USA Journal Surveys in Geophysics Online ISSN 1573-0956 Print ISSN 0169-3298

Description:    Mass balance estimates for the Antarctic Ice Sheet (AIS) in the 2007 report by the Intergovernmental Panel on Climate Change and in more recent reports lie between approximately +50 to −250 Gt/year for 1992 to 2009. The 300 Gt/year range is approximately 15% of the annual mass input and 0.8 mm/year Sea Level Equivalent (SLE). Two estimates from radar altimeter measurements of elevation change by European Remote-sensing Satellites (ERS) (+28 and −31 Gt/year) lie in the upper part, whereas estimates from the Input-minus-Output Method (IOM) and the Gravity Recovery and Climate Experiment (GRACE) lie in the lower part (−40 to −246 Gt/year). We compare the various estimates, discuss the methodology used, and critically assess the results. We also modify the IOM estimate using (1) an alternate extrapolation to estimate the discharge from the non-observed 15% of the periphery, and (2) substitution of input from a field data compilation for input from an atmospheric model in 6% of area. The modified IOM estimate reduces the loss from 136 Gt/year to 13 Gt/year. Two ERS-based estimates, the modified IOM, and a GRACE-based estimate for observations within 1992–2005 lie in a narrowed range of +27 to −40 Gt/year, which is about 3% of the annual mass input and only 0.2 mm/year SLE. Our preferred estimate for 1992–2001 is −47 Gt/year for West Antarctica, +16 Gt/year for East Antarctica, and −31 Gt/year overall (+0.1 mm/year SLE), not including part of the Antarctic Peninsula (1.07% of the AIS area). Although recent reports of large and increasing rates of mass loss with time from GRACE-based studies cite agreement with IOM results, our evaluation does not support that conclusion. Content Type Journal Article Pages 1-26 DOI 10.1007/s10712-011-9123-5 Authors H. Jay Zwally, Cryospheric Sciences Branch Code 614. 1, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA Mario B. Giovinetto, SGT Inc, Cryospheric Sciences Branch Code 614. 1, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA Journal Surveys in Geophysics Online ISSN 1573-0956 Print ISSN 0169-3298

Description: Preface to the Special Issue on “Arrays and Array Methods in Global Seismology” Content Type Journal Article Pages 269-270 DOI 10.1007/s10712-009-9080-4 Authors Y. Jeffrey Gu, University of Alberta Department of Physics Edmonton AB T6G 2G7 Canada Michael J. Rycroft, CAESAR Consultancy 35 Millington Road Cambridge CB3 9HW UK Journal Surveys in Geophysics Online ISSN 1573-0956 Print ISSN 0169-3298 Journal Volume Volume 30 Journal Issue Volume 30, Numbers 4-5

Description:    It is well acknowledged that there are large uncertainties associated with radar-based estimates of rainfall. Numerous sources of these errors are due to parameter estimation, the observational system and measurement principles, and not fully understood physical processes. Propagation of these uncertainties through all models for which radar-rainfall are used as input (e.g., hydrologic models) or as initial conditions (e.g., weather forecasting models) is necessary to enhance the understanding and interpretation of the obtained results. The aim of this paper is to provide an extensive literature review of the principal sources of error affecting single polarization radar-based rainfall estimates. These include radar miscalibration, attenuation, ground clutter and anomalous propagation, beam blockage, variability of the Z – R relation, range degradation, vertical variability of the precipitation system, vertical air motion and precipitation drift, and temporal sampling errors. Finally, the authors report some recent results from empirically-based modeling of the total radar-rainfall uncertainties. The bibliography comprises over 200 peer reviewed journal articles. Content Type Journal Article Pages 107-129 DOI 10.1007/s10712-009-9079-x Authors Gabriele Villarini, Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08540, USA Witold F. Krajewski, IIHR-Hydroscience & Engineering, The University of Iowa, Iowa City, IA USA Journal Surveys in Geophysics Online ISSN 1573-0956 Print ISSN 0169-3298 Journal Volume Volume 31 Journal Issue Volume 31, Number 1