866 results on '"HENDRICKS, Stefan"'
Search Results
202. A weekly Arctic sea-ice thickness data record from merged CryoSat-2 and SMOS satellite data
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Ricker, Robert, primary, Hendricks, Stefan, additional, Kaleschke, Lars, additional, Tian-Kunze, Xiangshan, additional, King, Jennifer, additional, and Haas, Christian, additional
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- 2017
- Full Text
- View/download PDF
203. Satellite-observed drop of Arctic sea ice growth in winter 2015-2016
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Ricker, Robert, primary, Hendricks, Stefan, additional, Girard-Ardhuin, Fanny, additional, Kaleschke, Lars, additional, Lique, Camille, additional, Tian-Kunze, Xiangshan, additional, Nicolaus, Marcel, additional, and Krumpen, Thomas, additional
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- 2017
- Full Text
- View/download PDF
204. Sea-ice thickness from field measurements in the northwestern Barents Sea
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King, Jennifer, primary, Spreen, Gunnar, additional, Gerland, Sebastian, additional, Haas, Christian, additional, Hendricks, Stefan, additional, Kaleschke, Lars, additional, and Wang, Caixin, additional
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- 2017
- Full Text
- View/download PDF
205. Brief communication: Antarctic sea ice gain does not compensate for increased solar absorption from Arctic ice loss
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Katlein, Christian, primary, Hendricks, Stefan, additional, and Key, Jeffrey, additional
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- 2017
- Full Text
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206. Arctic in Rapid Transition: Priorities for the future of marine and coastal research in the Arctic
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Werner, Kirstin, Fritz, Michael, Morata, Nathalie, Keil, Kathrin, Pavlov, Alexey, Peeken, Ilka, Nikolopoulos, Anna, Findlay, Helen S., Kedra, Monika, Majaneva, Sanna, Renner, Angelika, Hendricks, Stefan, Jacquot, Mathilde, Nicolaus, Marcel, O'Regan, Matt, Sampei, Makoto, Wegner, Carolyn, Werner, Kirstin, Fritz, Michael, Morata, Nathalie, Keil, Kathrin, Pavlov, Alexey, Peeken, Ilka, Nikolopoulos, Anna, Findlay, Helen S., Kedra, Monika, Majaneva, Sanna, Renner, Angelika, Hendricks, Stefan, Jacquot, Mathilde, Nicolaus, Marcel, O'Regan, Matt, Sampei, Makoto, and Wegner, Carolyn
- Abstract
Understanding and responding to the rapidly occurring environmental changes in the Arctic over the past few decades require new approaches in science. This includes improved collaborations within the scientific community but also enhanced dialogue between scientists and societal stakeholders, especially with Arctic communities. As a contribution to the Third International Conference on Arctic Research Planning (ICARPIII), the Arctic in Rapid Transition (ART) network held an international workshop in France, in October 2014, in order to discuss high-priority requirements for future Arctic marine and coastal research from an early-career scientists (ECS) perspective. The discussion encompassed a variety of research fields, including topics of oceanographic conditions, sea-ice monitoring, marine biodiversity, land-ocean interactions, and geological reconstructions, as well as law and governance issues. Participants of the workshop strongly agreed on the need to enhance interdisciplinarity in order to collect comprehensive knowledge about the modern and past Arctic Ocean's geo-ecological dynamics. Such knowledge enables improved predictions of Arctic developments and provides the basis for elaborate decision-making on future actions under plausible environmental and climate scenarios in the high northern latitudes. Priority research sheets resulting from the workshop's discussions were distributed during the ICARPIII meetings in April 2015 in Japan, and are publicly available online.
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- 2016
- Full Text
- View/download PDF
207. Improved 1D inversions for sea ice thickness and conductivity from electromagnetic induction data : Inclusion of nonlinearities caused by passive bucking
- Author
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Hunkeler, Priska A., Hendricks, Stefan, Hoppmann, Mario, Farquharson, Colin G., Kalscheuer, Thomas, Grab, Melchior, Kaufmann, Manuela S., Rabenstein, Lasse, Gerdes, Rüdiger, Hunkeler, Priska A., Hendricks, Stefan, Hoppmann, Mario, Farquharson, Colin G., Kalscheuer, Thomas, Grab, Melchior, Kaufmann, Manuela S., Rabenstein, Lasse, and Gerdes, Rüdiger
- Abstract
The porosity of sea ice is a fundamental physical parameter that governs the mechanical strength of sea ice and the mobility of gases and nutrients for biological processes and biogeochemical cycles in the sea ice layer. However, little is known about the spatial distribution of the sea ice porosity and its variability between different sea ice types; an efficient and nondestructive method to measure this property is currently missing. Sea ice porosity is linked to the bulk electrical conductivity of sea ice, a parameter routinely used to discriminate between sea ice and seawater by electromagnetic (EM) induction sensors. Here, we have evaluated the prospect of porosity retrieval of sea ice by means of bulk conductivity estimates using 1D multi-frequency EM inversion schemes. We have focused on two inversion algorithms, a smoothness-constrained inversion and a Marquardt-Levenberg inversion, which we modified for the nonlinear signal bias caused by a passive bucking coil operated in such a highly conductive environment. Using synthetic modeling studies, 1D inversion algorithms and multiple frequencies, we found that we can resolve the sea ice conductivity within +/- 0.01 S/m. Using standard assumptions for the conductivity-porosity relation of sea ice, we were able to estimate porosity with an uncertainty of +/- 1.2%, which enables efficient and nondestructive surveys of the internal state of the sea ice cover.
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- 2016
- Full Text
- View/download PDF
208. A glimpse beneath Antarctic sea ice : Platelet layer volume from multifrequency electromagnetic induction sounding
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Hunkeler, Priska A., Hoppmann, Mario, Hendricks, Stefan, Kalscheuer, Thomas, Gerdes, Ruediger, Hunkeler, Priska A., Hoppmann, Mario, Hendricks, Stefan, Kalscheuer, Thomas, and Gerdes, Ruediger
- Abstract
In Antarctica, ice crystals emerge from ice-shelf cavities and accumulate in unconsolidated layers beneath nearby sea ice. Such sub-ice platelet layers form a unique habitat, and serve as an indicator for the state of an ice shelf. However, the lack of a suitable methodology impedes an efficient quantification of this phenomenon on scales beyond point measurements. In this study, we inverted multi-frequency electromagnetic (EM) induction soundings of > 100 km length, obtained on fast ice with an underlying platelet layer in the eastern Weddell Sea. EM-derived platelet-layer thickness and conductivity are consistent with other field observations. Our results further suggest that platelet-layer volume is higher than previously thought in this region, and that platelet-layer ice-volume fraction is proportional to its thickness. We conclude that multi-frequency EM is a suitable tool to determine platelet-layer volume, with the potential to obtain crucial knowledge of associated processes in otherwise inaccessible ice-shelf cavities.
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- 2016
- Full Text
- View/download PDF
209. Central Arctic Ocean freshwater during a period of anomalous melt and advection in 2015
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Rabe, Benjamin, Korhonen, Meri, Hoppmann, Mario, Ricker, Robert, Hendricks, Stefan, Krumpen, Thomas, Beckers, Justin, Schauer, Ursula, Rabe, Benjamin, Korhonen, Meri, Hoppmann, Mario, Ricker, Robert, Hendricks, Stefan, Krumpen, Thomas, Beckers, Justin, and Schauer, Ursula
- Abstract
During the recent decade the Arctic Ocean has shown several years of very low sea-ice extent and an increase in liquid freshwater. Yet, the processes underlying the interannual variability are still not fully understood. Hydrographic observations by ship campaigns and autonomous platforms reveal that summer 2015 showed above average liquid freshwater in the upper ocean of the central Arctic. Surface temperatures and sea level pressure were also higher than the average of the preceeding two decades. From hydrographic observations and atmospheric reanalysis data we show that this liquid freshwater anomaly is associated with above average sea-ice melt and intensified northward Ekman transport. We, further, found significant amounts of Pacific Water in the upper water column, from the mixed-layer to the upper halocline. Our results suggest that the freshening was due to both advection of low-salinity water from the direction of the Siberian shelves, the Beaufort Gyre and the Bering Strait, and enhance sea-ice melt.
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- 2016
210. CS2SMOS: Weekly Arctic Sea-Ice Thickness Data Record
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Ricker, Robert, Hendricks, Stefan, Kaleschke, Lars, Tian-Kunze, Xiangshan, Ricker, Robert, Hendricks, Stefan, Kaleschke, Lars, and Tian-Kunze, Xiangshan
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- 2016
211. Snow depth on Antarctic sea ice from autonomous measurements
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Nicolaus, Marcel, Arndt, Stefanie, Hendricks, Stefan, Heygster, Georg, Hoppmann, Mario, Huntemann, Marcus, Katlein, Christian, Langevin, Danielle, Rossmann, Leonard, Schwegmann, Sandra, König-Langlo, Gert, Nicolaus, Marcel, Arndt, Stefanie, Hendricks, Stefan, Heygster, Georg, Hoppmann, Mario, Huntemann, Marcus, Katlein, Christian, Langevin, Danielle, Rossmann, Leonard, Schwegmann, Sandra, and König-Langlo, Gert
- Abstract
The snow cover on sea ice received more and more attention in recent sea ice studies and model simulations, because its physical properties dominate many sea ice and upper ocean processes. In particular; the temporal and spatial distribution of snow depth is of crucial importance for the energy and mass budgets of sea ice, as well as for the interaction with the atmosphere and the oceanic freshwater budget. Snow depth is also a crucial parameter for sea ice thickness retrieval algorithms from satellite altimetry data. Recent time series of Arctic sea ice volume only use monthly snow depth climatology, which cannot take into account annual changes of the snow depth and its properties. For Antarctic sea ice, no such climatology is available. With a few exceptions, snow depth on sea ice is determined from manual in-situ measurements with very limited coverage of space and time. Hence the need for more consistent observational data sets of snow depth on sea ice is frequently highlighted. Here, we present time series measurements of snow depths on Antarctic sea ice, recorded by an innovative and affordable platform. This Snow Buoy is optimized to autonomously monitor the evolution of snow depth on sea ice and will allow new insights into its seasonality. In addition, the instruments report air temperature and atmospheric pressure directly into different international networks, e.g. the Global Telecommunication System (GTS). We introduce the Snow Buoy concept together with technical specifications and results on data quality, reliability, and performance of the units. We highlight the findings from four buoys, which simultaneously drifted through the Weddell Sea for more than 1.5 years, revealing unique information on characteristic regional and seasonal differences.
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- 2016
212. About the consistency between Envisat and CryoSat-2 radar freeboard retrieval over Antarctic sea ice
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Schwegmann, Sandra, Rinne, Eero, Ricker, Robert, Hendricks, Stefan, Helm, Veit, Schwegmann, Sandra, Rinne, Eero, Ricker, Robert, Hendricks, Stefan, and Helm, Veit
- Abstract
Knowledge about Antarctic sea-ice volume and its changes over the past decades has been sparse due to the lack of systematic sea-ice thickness measurements in this remote area. Recently, first attempts have been made to develop a sea-ice thickness product over the Southern Ocean from space-borne radar altimetry and results look promising. Today, more than 20 years of radar altimeter data are potentially available for such products. However, the characteristics of individual radar types differ for the available altimeter missions. Hence, it is important and our goal to study the consistency between single sensors in order to develop long and consistent time series. Here, the consistency between freeboard measurements of the Radar Altimeter 2 on board Envisat and freeboard measurements from the Synthetic-Aperture Interferometric Radar Altimeter on board CryoSat-2 is tested for their overlap period in 2011. Results indicate that mean and modal values are in reasonable agreement over the sea-ice growth season (May–October) and partly also beyond. In general, Envisat data show higher freeboards in the first-year ice zone while CryoSat-2 freeboards are higher in the multiyear ice zone and near the coasts. This has consequences for the agreement in individual sectors of the Southern Ocean, where one or the other ice class may dominate. Nevertheless, over the growth season, mean freeboard for the entire (regionally separated) Southern Ocean differs generally by not more than 3 cm (8 cm, with few exceptions) between Envisat and CryoSat-2, and the differences between modal freeboards lie generally within ±10 cm and often even below.
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- 2016
213. Online sea-ice knowledge and data platform <www.meereisportal.de>
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Grosfeld, Klaus, Treffeisen, Renate, Asseng, Jölund, Bartsch, Annekathrin, Bräuer, Benny, Fritzsch, Bernadette, Gerdes, Rüdiger, Hendricks, Stefan, Hiller, Wolfgang, Heygster, Georg, Krumpen, Thomas, Lemke, Peter, Melsheimer, Christian, Nicolaus, Marcel, Ricker, Robert, Weigelt, Marietta, Grosfeld, Klaus, Treffeisen, Renate, Asseng, Jölund, Bartsch, Annekathrin, Bräuer, Benny, Fritzsch, Bernadette, Gerdes, Rüdiger, Hendricks, Stefan, Hiller, Wolfgang, Heygster, Georg, Krumpen, Thomas, Lemke, Peter, Melsheimer, Christian, Nicolaus, Marcel, Ricker, Robert, and Weigelt, Marietta
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- 2016
214. User Guide - AWI CryoSat-2 Sea Ice Thickness Data Product (v1.2)
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Hendricks, Stefan, Ricker, Robert, Helm, Veit, Hendricks, Stefan, Ricker, Robert, and Helm, Veit
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User documentation of the AWI CryoSat-2 sea ice data product (v1.2, July 2016)
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- 2016
215. The Impact of Geophysical Corrections on Sea-Ice Freeboard Retrieved from Satellite Altimetry
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Ricker, Robert, Hendricks, Stefan, Beckers, Justin, Ricker, Robert, Hendricks, Stefan, and Beckers, Justin
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- 2016
216. SMOS sea ice product: Operational application and validation in the Barents Sea marginal ice zone
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Kaleschke, Lars, Tian-Kunze, Xiangshan, Maaß, Nina, Beitsch, Alexander, Wernecke, Andreas, Miernecki, Maciej, Müller, Gerd, Fock, Björn D., Gierisch, Andrea M. U., Heinke Schlünzen, Katharina, Pohlmann, Thomas, Dobrynin, Mikhail, Hendricks, Stefan, Asseng, Jölung, Gerdes, Rüdiger, Jochmann, Peter, Reimer, Nils, Holfort, Jürgen, Melsheimer, Christian, Heygster, Georg, Spreen, Gunnar, Gerland, Sebastian, King, Jennifer, Skou, Niels, Søbjærg, Sten Schmidl, Haas, Christian, Richter, Friedrich, Casal, Tânia, Kaleschke, Lars, Tian-Kunze, Xiangshan, Maaß, Nina, Beitsch, Alexander, Wernecke, Andreas, Miernecki, Maciej, Müller, Gerd, Fock, Björn D., Gierisch, Andrea M. U., Heinke Schlünzen, Katharina, Pohlmann, Thomas, Dobrynin, Mikhail, Hendricks, Stefan, Asseng, Jölung, Gerdes, Rüdiger, Jochmann, Peter, Reimer, Nils, Holfort, Jürgen, Melsheimer, Christian, Heygster, Georg, Spreen, Gunnar, Gerland, Sebastian, King, Jennifer, Skou, Niels, Søbjærg, Sten Schmidl, Haas, Christian, Richter, Friedrich, and Casal, Tânia
- Abstract
Brightness temperatures at 1.4 GHz (L-band) measured by the Soil Moisture and Ocean Salinity (SMOS) Mission have been used to derive the thickness of sea ice. The retrieval method is applicable only for relatively thin ice and not during the melting period. Hitherto, the availability of ground truth sea ice thickness measurements for validation of SMOS sea ice products was mainly limited to relatively thick ice. The situation has improved with an extensive field campaign in the Barents Sea during an anomalous ice edge retreat and subsequent freeze-up event in March 2014. A sea ice forecast system for ship route optimisation has been developed and was tested during this field campaign with the ice-strengthened research vessel RV Lance. The ship cruise was complemented with coordinated measurements from a helicopter and the research aircraft Polar 5. Sea ice thickness was measured using an electromagnetic induction (EM) system from the bow of RV Lance and another EM-system towed below the helicopter. Polar 5 was equipped among others with the L-band radiometer EMIRAD-2. The experiment yielded a comprehensive data set allowing the evaluation of the operational forecast and route optimisation system as well as the SMOS-derived sea ice thickness product that has been used for the initialization of the forecasts. Two different SMOS sea ice thickness products reproduce the main spatial patterns of the ground truth measurements while the main difference being an underestimation of thick deformed ice. Ice thicknesses derived from the surface elevation measured by an airborne laser scanner and from simultaneous EMIRAD-2 brightness temperatures correlate well up to 1.5 m which is more than the previously anticipated maximal SMOS retrieval thickness.
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- 2016
217. A glimpse beneath Antarctic sea ice: observation of platelet-layer thickness and ice-volume fraction with multi-frequency EM
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Hoppmann, Mario, Hunkeler, Priska, Hendricks, Stefan, Kalscheuer, Thomas, Gerdes, Rüdiger, Hoppmann, Mario, Hunkeler, Priska, Hendricks, Stefan, Kalscheuer, Thomas, and Gerdes, Rüdiger
- Abstract
In Antarctica, ice crystals (platelets) form and grow in supercooled waters below ice shelves. These platelets rise, accumulate beneath nearby sea ice, and subsequently form a several meter thick, porous sub-ice platelet layer. This special ice type is a unique habitat, influences sea-ice mass and energy balance, and its volume can be interpreted as an indicator of the health of an ice shelf. Although progress has been made in determining and understanding its spatio-temporal variability based on point measurements, an investigation of this phenomenon on a larger scale remains a challenge due to logistical constraints and a lack of suitable methodology. In the present study, we applied a lateral constrained Marquardt-Levenberg inversion to a unique multi-frequency electromagnetic (EM) induction sounding dataset obtained on the ice-shelf influenced fast-ice regime of Atka Bay, eastern Weddell Sea. We adapted the inversion algorithm to incorporate a sensor specific signal bias, and confirmed the reliability of the algorithm by performing a sensitivity study using synthetic data. We inverted the field data for sea-ice and platelet-layer thickness and electrical conductivity, and calculated ice-volume fractions within the platelet layer using Archie’s Law. The thickness results agreed well with drillhole validation datasets within the uncertainty range, and the ice-volume fraction yielded results comparable to other studies. Both parameters together enable an estimation of the total ice volume within the platelet layer, which was found to be comparable to the volume of landfast sea ice in this region, and corresponded to more than a quarter of the annual basal melt volume of the nearby Ekström Ice Shelf. Our findings show that multi-frequency EM induction sounding is a suitable approach to efficiently map sea-ice and platelet-layer properties, with important implications for research into ocean/ice-shelf/sea-ice interactions. However, a successful application of this te
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- 2016
218. A Pan-Arctic Airborne Sea Ice Observation System
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Hendricks, Stefan, Haas, Christian, Gerland, Sebastian, Herber, Andreas, Krumpen, Thomas, Mahoney, Andy, Eicken, Hajo, Gerdes, Rüdiger, Hendricks, Stefan, Haas, Christian, Gerland, Sebastian, Herber, Andreas, Krumpen, Thomas, Mahoney, Andy, Eicken, Hajo, and Gerdes, Rüdiger
- Abstract
We present an Arctic sea-ice observation system that focuses on unique direct observations of sea ice plus snow thickness. A network of research institutions, the Alfred Wegener Institute, York University and the Norwegian Polar Institute, maintain an observation system that is embedded in several national and international projects and supported by research partners. Activities in the field include the use of long-range polar research aircraft and helicopter operations from research icebreakers and bases on land. Data collections are based on electromagnetic induction sounding and consistent time series are available in key regions of the Arctic Ocean since 2001. The increased use of polar research aircrafts in recent years has resulted in several initiatives that aim for long-term observations of ice thickness during seasonal minimum and maximum sea-ice extent in the Arctic. The scientific payload of the research aircraft of type Basler BT-67 and its capability to fly low-altitude surveys makes it an ideal tool for the validation and on-going verification of various satellite remote sensing products. The availability of airborne sea-ice thickness information spans the periods of different satellite sea-ice thickness retrieval concepts, such as the radar altimeters from Envisat and CryoSat-2 as well as the laser altimeter from ICESat-1 and -2. Wherever possible, the airborne surveys are accompanied by in-situ observations on the ice surface to compile a hierarchy of validation data from local to basin scales. Results of the observation network have found broad use for studying inter-annual variability and changes of sea ice thickness as well as the validation of satellite data products. We identify a gap of observations over the multi-year sea ice zone during the melt season and early freeze-up. We also stress the need for the continuation of a coordinated observational program that has produced a time series of sea ice thickness only paralleled by submarine observ
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- 2016
219. Recent summer sea ice thickness surveys in Fram Strait and associated ice volume fluxes
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Krumpen, Thomas, Gerdes, Rüdiger, Haas, Christian, Hendricks, Stefan, Herber, Andreas, Selyuzhenok, Lera, Smedsrud, L. H., Spreen, Gunnar, Krumpen, Thomas, Gerdes, Rüdiger, Haas, Christian, Hendricks, Stefan, Herber, Andreas, Selyuzhenok, Lera, Smedsrud, L. H., and Spreen, Gunnar
- Abstract
Fram Strait is the main gateway for sea ice export out of the Arctic Ocean, and therefore observations there give insight into the composition and properties of Arctic sea ice in general and how it varies over time. A data set of ground-based and airborne electromagnetic ice thickness measurements collected during summer between 2001 and 2012 is presented here, including long transects well into the southern part of the Transpolar Drift obtained using fixed-wing aircrafts. The primary source of the surveyed sea ice leaving Fram Strait is the Laptev Sea and its age has decreased from 3 to 2 years between 1990 and 2012. The thickness data consistently also show a general thinning of sea ice for the last decade, with a decrease in modal thickness of second year and multiyear ice, and a decrease in mean thickness and fraction of ice thicker than 3 m. Local melting in the strait was investigated in two surveys performed in the downstream direction, showing a decrease in sea ice thickness of 0.19 m degree−1 latitude south of 81° N. Further north variability in ice thickness is more related to differences in age and deformation. The thickness observations were combined with ice area export estimates to calculate summer volume fluxes of sea ice. While satellite data show that monthly ice area export had positive trends since 1980 (10.9 × 103 km2 decade−1), the summer (July and August) ice area export is low with high uncertainties. The average volume export amounts to 16.78 km3. Naturally, the volume flux estimates are limited to the period when airborne thickness surveys are available. Nevertheless, we could show that the combination of satellite data and airborne observations can be used to determine volume fluxes through Fram Strait and as such, can be used to bridge the lack of satellite-based sea ice thickness information in summer.
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- 2016
220. Improved 1D inversions for sea ice thickness and conductivity from electromagnetic induction data: Inclusion of nonlinearities caused by passive bucking
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Hunkeler, Priska, Hendricks, Stefan, Hoppmann, Mario, Farquharson, Colin, Kalscheuer, Thomas, Grab, Melchior, Kaufmann, Manuela S., Rabenstein, Lasse, Gerdes, Rüdiger, Hunkeler, Priska, Hendricks, Stefan, Hoppmann, Mario, Farquharson, Colin, Kalscheuer, Thomas, Grab, Melchior, Kaufmann, Manuela S., Rabenstein, Lasse, and Gerdes, Rüdiger
- Abstract
The porosity of sea ice is a fundamental physical parameter that governs the mechanical strength of sea ice and the mobility of gases and nutrients for biological processes and biogeochemical cycles in the sea ice layer. However, little is known about the spatial distribution of the sea ice porosity and its variability between different sea ice types; an efficient and nondestructive method to measure this property is currently missing. Sea ice porosity is linked to the bulk electrical conductivity of sea ice, a parameter routinely used to discriminate between sea ice and seawater by electromagnetic (EM) induction sensors. Here, we have evaluated the prospect of porosity retrieval of sea ice by means of bulk conductivity estimates using 1D multifrequency EM inversion schemes. We have focused on two inversion algorithms, a smoothness-constrained inversion and a Marquardt-Levenberg inversion, which we modified for the nonlinear signal bias caused by a passive bucking coil operated in such a highly conductive environment. Using synthetic modeling studies, 1D inversion algorithms and multiple frequencies, we found that we can resolve the sea ice conductivity within +-0.01 S∕m. Using standard assumptions for the conductivity- porosity relation of sea ice, we were able to estimate porosity with an uncertainty of +-1.2%, which enables efficient and nondestructive surveys of the internal state of the sea ice cover.
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- 2016
221. A glimpse beneath Antarctic sea ice: platelet-layer volume from multi-frequency electromagnetic induction sounding
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Hunkeler, Priska, Hoppmann, Mario, Hendricks, Stefan, Kalscheuer, Thomas, Gerdes, Rüdiger, Hunkeler, Priska, Hoppmann, Mario, Hendricks, Stefan, Kalscheuer, Thomas, and Gerdes, Rüdiger
- Abstract
In Antarctica, ice crystals emerge from ice shelf cavities and accumulate in unconsolidated layers beneath nearby sea ice. Such sub-ice platelet layers form a unique habitat and serve as an indicator for the state of an ice shelf. However, the lack of a suitable methodology impedes an efficient quantification of this phenomenon on scales beyond point measurements. In this study, we inverted multifrequency electromagnetic (EM) induction soundings, obtained on fast ice with an underlying platelet layer along profiles of >100 km length in the eastern Weddell Sea. EM-derived platelet layer thickness and conductivity are consistent with other field observations. Our results suggest that platelet layer volume is higher than previously thought in this region and that platelet layer ice volume fraction is proportional to its thickness. We conclude that multifrequency EM is a suitable tool to determine platelet layer volume, with the potential to obtain crucial knowledge of associated processes in otherwise inaccessible ice shelf cavities.
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- 2016
222. Uncertainties of Sea Ice Thickness from CryoSat-2
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Hendricks, Stefan, Ricker, Robert, Helm, Veit, Haas, Christian, and Davidson, Malcom
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- 2014
223. Advances in Electromagnetic Induction Sounding of Sea-Ice Thickness
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Hendricks, Stefan, Hunkeler, Priska, Pfaffhuber, Andreas. A., Vöge, Malte, and Haas, Christian
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- 2014
224. Platelet-Layer Volume with Electromagnetic Induction Sounding
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Hunkeler, Priska, Hendricks, Stefan, Hoppmann, Mario, and Paul, Stephan
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- 2014
225. Physical Sea Ice Properties in the Winter Weddell Sea in 2013
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Hendricks, Stefan, Schwegmann, Sandra, Krumpen, Thomas, Hunkeler, Priska, Ricker, Robert, Hoppmann, Mario, Arndt, Stefanie, and Nicolaus, Marcel
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- 2014
226. Effects of different footprint areas on the comparability between measurements of sea ice freeboard
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Schwegmann, Sandra, Hendricks, Stefan, Haas, Christian, and Herber, Andreas
- Abstract
The significant loss of Arctic sea ice during the last decades shows the sensitivity of the sea-ice system to changes in global climate. To distinguish between natural variability and the impact of global warming, an understanding of processes and feedbacks is necessary, and for that, consistent and comprehensive measurements of the most important sea-ice properties are required. While sea-ice concentration is observed routinely year-round since the beginning of the satellite era, strategies to investigate the sea-ice thickness distribution have been developed only recently. These are crucially required for an examination of sea-ice mass changes. Presently, ice thickness observations are mainly based on freeboard measurements by means of satellite laser and radar altimetry. To contribute to the interpretation of these sea-ice thickness products, available airborne thickness and freeboard data were collected within the Sea Ice Downstream Services for Arctic and Antarctic Users and Stakeholders (SIDARUS) EU-Project, and have been analyzed with respect to their usability for the validation of the large-scale satellite products. One major challenge in comparing satellite and airborne measurements is the different footprint area of these methods. Therefore, statistical parameters like the variability of freeboard within the common footprint areas have been analyzed from measurements made during the PAMARCMIP 2011 campaign in order to determine the differences between point measurements and areal averages. It turned out that mean freeboard is less dependent of the freeboard areas than the modal values are. Furthermore, differences in modal and mean values for the range of chosen footprint areas have been related to their dependency on different ice characteristics and length scales of freeboard and thickness profiles. Also for this comparison, mean values are found to be more representative, as the results are mostly independent from the footprint but depend more on the length scales. However, there was no length scale that was representative for all the observed regions. Finally, results will be used for the interpretation of the comparison between freeboard and sea-ice thickness data derived from different data sources using laser and radar altimetry.
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- 2014
227. Winter sea-ice thicknesses in the Weddell Sea and their variability over the past 24 years
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Schwegmann, Sandra, Hunkeler, Priska, Hendricks, Stefan, Lemke, Peter, Haas, Christian, Krumpen, Thomas, and Ricker, Robert
- Abstract
The sea-ice thickness distribution is one of the most important sea-ice properties, but also one of the less frequently observed ones so far. Satellite retrievals of Antarctic sea-ice thickness are currently limited to laser and radar altimetry observations of snow freeboard with large uncertainties, and electromagnetic measurements have been obtained only sporadically. For the investigation of the variability and changes in the sea-ice thickness distribution over the last decades, data are mainly available from very basic methods such as drilling or ship-based observations following the Antarctic Sea Ice Processes and Climate (ASPeCt) protocol. Thereby it is an advantage that those data also include information on the snow-depth and partly on the sea-ice freeboard distribution, which are as sparse as information on the sea-ice thickness distribution, in particular during winter conditions. The most recent data based on those methods were obtained during austral winter 2013, when various sea-ice parameters were measured in the Weddell Sea as part of the Antarctic Winter Ecosystem Climate Study (AWECS). Here, we present first results of the sea-ice thickness, freeboard and snow-depth distribution obtained by drill-hole measurements from this expedition. The new data set is compared with results from three previous winter campaigns done in 1989, 1992 and 2006 in the Weddell Sea in order to determine the long-term variability of sea-ice thickness, snow depth and freeboard. A challenge in comparing all those data is that measurement sites are based only on individual floes, which are expected to be representative for an entire region. In addition, sampling rates differ between the considered field experiments. Therefore, drill-hole thicknesses are cross-correlated with ground-based EM-measurements in order to identify for the newest data set, how representative the chosen study areas have been for the respective sea-ice floes and which consequences different measurement spacing has for the comparison of data from different years.
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- 2014
228. Sea-ice buoy deployments during ANT-XXIX/6 & ANT-XXIX/9
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Schwegmann, Sandra, Nicolaus, Marcel, Castellani, Giulia, Heil, Petra, Leonard, Katherine, White, Seth, Wever, Nander, Lange, Benjamin, Hendricks, Stefan, Hoppmann, Mario, Rigor, Ignatius, Hutchings, Jennifer K., and Flores, Hauke
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- 2014
229. Iceflux: Ice-ecosystem carbon flux in Polar oceans
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Lange, Benjamin, Kohlbach, Doreen, David, Carmen, Flores, Hauke, Peeken, Ilka, Nicolaus, Marcel, Katlein, Christian, Krumpen, Thomas, and Hendricks, Stefan
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- 2014
230. Arctic in Rapid Transition: Priorities for the future of marine and coastal research in the Arctic
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Werner, Kirstin, primary, Fritz, Michael, additional, Morata, Nathalie, additional, Keil, Kathrin, additional, Pavlov, Alexey, additional, Peeken, Ilka, additional, Nikolopoulos, Anna, additional, Findlay, Helen S., additional, Kędra, Monika, additional, Majaneva, Sanna, additional, Renner, Angelika, additional, Hendricks, Stefan, additional, Jacquot, Mathilde, additional, Nicolaus, Marcel, additional, O'Regan, Matt, additional, Sampei, Makoto, additional, and Wegner, Carolyn, additional
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- 2016
- Full Text
- View/download PDF
231. About the consistency between Envisat and CryoSat-2 radar freeboard retrieval over Antarctic sea ice
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Schwegmann, Sandra, primary, Rinne, Eero, additional, Ricker, Robert, additional, Hendricks, Stefan, additional, and Helm, Veit, additional
- Published
- 2016
- Full Text
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232. SMOS sea ice product: Operational application and validation in the Barents Sea marginal ice zone
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Kaleschke, Lars, primary, Tian-Kunze, Xiangshan, additional, Maaß, Nina, additional, Beitsch, Alexander, additional, Wernecke, Andreas, additional, Miernecki, Maciej, additional, Müller, Gerd, additional, Fock, Björn H., additional, Gierisch, Andrea M.U., additional, Schlünzen, K. Heinke, additional, Pohlmann, Thomas, additional, Dobrynin, Mikhail, additional, Hendricks, Stefan, additional, Asseng, Jölund, additional, Gerdes, Rüdiger, additional, Jochmann, Peter, additional, Reimer, Nils, additional, Holfort, Jürgen, additional, Melsheimer, Christian, additional, Heygster, Georg, additional, Spreen, Gunnar, additional, Gerland, Sebastian, additional, King, Jennifer, additional, Skou, Niels, additional, Søbjærg, Sten Schmidl, additional, Haas, Christian, additional, Richter, Friedrich, additional, and Casal, Tânia, additional
- Published
- 2016
- Full Text
- View/download PDF
233. The Impact of Geophysical Corrections on Sea-Ice Freeboard Retrieved from Satellite Altimetry
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Ricker, Robert, primary, Hendricks, Stefan, additional, and Beckers, Justin, additional
- Published
- 2016
- Full Text
- View/download PDF
234. Improved 1D inversions for sea ice thickness and conductivity from electromagnetic induction data: Inclusion of nonlinearities caused by passive bucking
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Hunkeler, Priska A., primary, Hendricks, Stefan, additional, Hoppmann, Mario, additional, Farquharson, Colin G., additional, Kalscheuer, Thomas, additional, Grab, Melchior, additional, Kaufmann, Manuela S., additional, Rabenstein, Lasse, additional, and Gerdes, Rüdiger, additional
- Published
- 2016
- Full Text
- View/download PDF
235. Impact of snow accumulation on CryoSat-2 range retrievals over Arctic sea ice: An observational approach with buoy data
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Ricker, Robert, Hendricks, Stefan, Perovich, Donald K., Helm, Veit, Gerdes, Rüdiger, Ricker, Robert, Hendricks, Stefan, Perovich, Donald K., Helm, Veit, and Gerdes, Rüdiger
- Abstract
Radar altimetry measurements of the current satellite mission CryoSat-2 show an increase of Arctic sea ice thickness in autumn 2013, compared to previous years but also related to March 2013. Such an increase over the melting season seems unlikely and needs to be investigated. Recent studies show that the influence of the snow cover is not negligible and can highly affect the CryoSat-2 range retrievals if it is assumed that the main scattering horizon is given by the snow-ice interface. Our analysis of Arctic ice mass balance buoy records and coincident CryoSat-2 data between 2012 and 2014 adds observational evidence to these findings. Linear trends of snow and ice freeboard measurements from buoys and nearby CryoSat-2 freeboard retrievals are calculated during accumulation events. We find a positive correlation between buoy snow freeboard and CryoSat-2 freeboard estimates, revealing that early snow accumulation might have caused a bias in CryoSat-2 sea ice thickness in autumn 2013.
- Published
- 2015
236. Towards an estimation of sub-sea-ice platelet-layer volume with multi-frequency electromagnetic induction sounding
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Hunkeler, Priska A., Hendricks, Stefan, Hoppmann, Mario, Paul, Stephan, Gerdes, Rüdiger, Hunkeler, Priska A., Hendricks, Stefan, Hoppmann, Mario, Paul, Stephan, and Gerdes, Rüdiger
- Abstract
Ice-platelet clusters modify the heat and mass balance of sea ice near Antarctic ice shelves and provide a unique habitat for ice-associated organisms. The amount and distribution of these ice crystals below the solid sea ice provide insight into melt rates and circulation regimes in the ice-shelf cavities, which are difficult to observe directly. However, little is known about the circum-Antarctic volume of the sub-sea-ice platelet layer, because observations have mostly been limited to point measurements. In this study, we present a new application of multi-frequency electromagnetic (EM) induction sounding to quantify platelet-layer properties. Combining in situ data with the theoretical response yields a bulk platelet-layer conductivity of 1154 +/- 271 mSm–1 and ice-volume fractions of 0.29–0.43. Calibration routines and uncertainties are discussed in detail to facilitate future studies. Our results suggest that multi-frequency EM induction sounding is a promising method to efficiently map platelet-layer volume on a larger scale than has previously been feasible.
- Published
- 2015
237. Classification of CryoSat-2 Radar Echoes
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Lohmann, Gerrit, Meggers, Helge, Unnithan, Vikram, Wolf-Gladrow, Dieter, Notholt, Justus, Bracher, Astrid, Ricker, Robert, Hendricks, Stefan, Helm, Veit, Gerdes, Rüdiger, Lohmann, Gerrit, Meggers, Helge, Unnithan, Vikram, Wolf-Gladrow, Dieter, Notholt, Justus, Bracher, Astrid, Ricker, Robert, Hendricks, Stefan, Helm, Veit, and Gerdes, Rüdiger
- Abstract
Sea-ice thickness at global scale is an important variable in the polar climate system. Only satellite altimeters such as onboard the CryoSat-2 mission allow us to obtain sea-ice thickness on hemispherical scale. Accurate CryoSat-2 altimeter range measurements provide surface elevations which have to be referenced to the local sea level to obtain sea-ice freeboard that can be converted into sea-ice thickness assuming hydrostatic equilibrium. The local sea-surface height is determined by careful detection of leads in the ice surface using the specific characteristics of the radar signal. Off-nadir reflections from leads can significantly affect the range retracking and hence bias the surface elevations of leads and sea ice. This can finally lead to a negative freeboard and hence also affects the thickness and volume retrieval. We present a method for the classification of CryoSat-2 radar echoes to correctly discriminate between valid and off-nadir biased echoes. We apply our classification to a CryoSat-2 track from December 15 where 50 leads over a distance of 2,300 km are identified. Overall 22 % of the surface elevations are associated with biased radar echoes.
- Published
- 2015
238. Evaluation of CryoSat-2 derived sea-ice freeboard over fast ice in McMurdo Sound, Antarctica
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Price, D., Beckers, Justin M., Ricker, Robert, Kurtz, Nathan, Rack, Wolfgang, Haas, Christian, Helm, Veit, Hendricks, Stefan, Leonard, G., Langhorn, P., Price, D., Beckers, Justin M., Ricker, Robert, Kurtz, Nathan, Rack, Wolfgang, Haas, Christian, Helm, Veit, Hendricks, Stefan, Leonard, G., and Langhorn, P.
- Abstract
Using in situ data from 2011 and 2013, we evaluate the ability of CryoSat-2 (CS-2) to retrieve sea-ice freeboard over fast ice in McMurdo Sound. This provides the first systematic validation of CS-2 in the coastal Antarctic and offers insight into the assumptions currently used to process CS-2 data. European Space Agency Level 2 (ESAL2) data are compared with results of a Waveform Fitting (WfF) procedure and a Threshold-First-Maximum-Retracker-Algorithm employed at 40% (TFMRA40). A supervised freeboard retrieval procedure is used to reduce errors associated with sea surface height identification and radar velocity in snow. We find ESAL2 freeboards located between the ice and snow freeboard rather than the frequently assumed snow/ice interface. WfF is within 0.04m of the ice freeboard but is influenced by variable snow conditions causing increased radar backscatter from the air/snow interface. Given such snow conditions and additional uncertainties in sea surface height identification, a positive bias of 0.14m away from the ice freeboard is observed. TFMRA40 freeboards are within 0.03m of the snow freeboard. The separation of freeboard estimates is primarily driven by the different assumptions of each retracker, although waveform alteration by variations in snow properties and surface roughness is evident. Techniques are amended where necessary, and automatic freeboard retrieval procedures for ESAL2, WfF and TFMRA40 are presented. CS-2 detects annual fastice freeboard trends using all three automatic procedures that are in line with known sea-ice growth rates in the region.
- Published
- 2015
239. Validation of SMOS sea ice thickness retrieval in the northern Baltic Sea
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Maaß, Nina, Kaleschke, Lars, Tian-Kunze, Xiangshan, Mäkynen, Marko, Drusch, Matthias, Krumpen, Thomas, Hendricks, Stefan, Lensu, Mikko, Haapala, Jari, Haas, Christian, Maaß, Nina, Kaleschke, Lars, Tian-Kunze, Xiangshan, Mäkynen, Marko, Drusch, Matthias, Krumpen, Thomas, Hendricks, Stefan, Lensu, Mikko, Haapala, Jari, and Haas, Christian
- Abstract
The Soil Moisture and Ocean Salinity (SMOS) mission observes brightness temperatures at a low microwave frequency of 1.4 GHz (L-band) with a daily coverage of the polar regions. L-band radiometry has been shown to provide information on the thickness of thin sea ice. Here, we apply a new emission model that has previously been used to investigate the impact of snow on thick Arctic sea ice. The model has not yet been used to retrieve ice thickness. In contrast to previous SMOS ice thickness retrievals, the new model allows us to include a snow layer in the brightness temperature simulations. Using ice thickness estimations from satellite thermal imagery, we simulate brightness temperatures during the ice growth season 2011 in the northern Baltic Sea. In both the simulations and the SMOS observations, brightness temperatures increase by more than 20 K, most likely due to an increase of ice thickness. Only if we include the snow in the model, the absolute values of the simulations and the observations agree well (mean deviations below 3.5 K). In a second comparison, we use high-resolution measurements of total ice thickness (sum of ice and snow thickness) from an electromagnetic (EM) sounding system to simulate brightness temperatures for 12 circular areas. While the SMOS observations and the simulations that use the EM modal ice thickness are highly correlated (r2=0.95), the simulated brightness temperatures are on average 12 K higher than observed by SMOS. This would correspond to an 8-cm overestimation of the modal ice thickness by the SMOS retrieval. In contrast, if the simulations take into account the shape of the EM ice thickness distributions (r2=0.87), the mean deviation between simulated and observed brightness temperatures is below 0.1 K.
- Published
- 2015
240. Taking a look at both sides of the ice: comparison of ice thickness and drift speed as observed from moored, airborne and shore-based instruments near Barrow, Alaska
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Mahoney, Andrew, Eicken, Hajo, Fukamachi, Yasushi, Ohshima, Kay I., Simizu, Daisuke, Kambhamettu, Chandra, Rovith, M. V., Hendricks, Stefan, Jones, Joshua, Mahoney, Andrew, Eicken, Hajo, Fukamachi, Yasushi, Ohshima, Kay I., Simizu, Daisuke, Kambhamettu, Chandra, Rovith, M. V., Hendricks, Stefan, and Jones, Joshua
- Abstract
Data from the Seasonal Ice Zone Observing Network (SIZONet) acquired near Barrow, Alaska, during the 2009/10 ice season allow novel comparisons between measurements of ice thickness and velocity. An airborne electromagnetic survey that passed over a moored Ice Profiling Sonar (IPS) provided coincident independent measurements of total ice and snow thickness and ice draft at a scale of 10 km. Once differences in sampling footprint size are accounted for, we reconcile the respective probability distributions and estimate the thickness of level sea ice at 1.48 +/- 0.1 m, with a snow depth of 0.12 +/- 0.07 m. We also complete what we believe is the first independent validation of radar-derived ice velocities by comparing measurements from a coastal radar with those from an under-ice acoustic Doppler current profiler (ADCP). After applying a median filter to reduce high-frequency scatter in the radar-derived data, we find good agreement with the ADCP bottom-tracked ice velocities. With increasing regulatory and operational needs for sea-ice data, including the number and thickness of pressure ridges, coordinated observing networks such as SIZONet can provide the means of reducing uncertainties inherent in individual datasets.
- Published
- 2015
241. Validation of SMOS sea ice thickness retrieval in the northern Baltic Sea
- Author
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Maaß, Nina, primary, Kaleschke, Lars, additional, Tian–Kunze, Xiangshan, additional, Mäkynen, Marko, additional, Drusch, Matthias, additional, Krumpen, Thomas, additional, Hendricks, Stefan, additional, Lensu, Mikko, additional, Haapala, Jari, additional, and Haas, Christian, additional
- Published
- 2015
- Full Text
- View/download PDF
242. CryoSat-2 Sea-Ice Freeboard and Thickness
- Author
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Hendricks, Stefan, Ricker, Robert, Helm, Veit, Haas, Christian, Skourup, Henriette, Herber, Andreas, Schwegmann, Sandra, Gerdes, Rüdiger, and Davidson, Malcom
- Abstract
The understanding and predictability of the observed decline of Arctic sea ice depends on the knowledge of its mass balance in a warming environment. While sea ice extent is monitored by passive microwave sensors for decades, only recently its volume is measured by basin-scale sea ice thickness observations of satellite altimetry missions. The current sea ice thickness sensor is SIRAL, a synthetic aperture radar altimeter on-board ESAs CryoSat-2. Altimetry missions measure freeboard, the height of the ice surface above the local water level, which can be converted into sea ice thickness. The conversion is very sensitive to errors in the freeboard retrieval and uncertainties in input parameters for the freeboard-tothickness conversion. Snow on Arctic sea ice plays a crucial role, since its regional variable physical parameters control the penetration of the Ku-Band radar waves and snow depth is required for the sea ice thickness retrieval algorithm, but not measured Arctic-wide. We present Arctic sea ice freeboard and thickness maps from CryoSat-2. The results are compared to available airborne validation datasets, which have been collected in an international validation program (CryoVEx). Sea ice thickness datasets obtained by airborne electromagnetic inductions sounding are available in Arctic spring of 2011 and 2012 and late summer of 2012 to quantify the uncertainties of the CryoSat-2 Arctic sea ice thickness data product of the Alfred Wegener Institute. Compared to the Arctic, only few validation datasets exist for CryoSat-2 sea ice data in the southern Ocean. We present the layout and first results of CryoSat-2 validation campaigns in the Weddell and Bellingshausen Seas between June and October 2013. The complicated snow properties of Antarctic sea ice may increase the uncertainty of CryoSat-2 sea ice thickness data, however sea ice volume estimates in the southern hemisphere are needed as well to understand the contrasting increase of Antarctic sea ice area.
- Published
- 2013
243. Multi-Frequency Electromagnetics for Sea-Ice Thickness Retrieval
- Author
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Hunkeler, Priska, Hendricks, Stefan, Hoppmann, Mario, and Gerdes, Rüdiger
- Published
- 2013
244. Developments in frequency domain AEM; tackling drift and noise with a multicomponent, ferrite-core, receiver tipplet
- Author
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Pfaffhuber, A. A., Kvistedal, Yme, Hendricks, Stefan, Lied, Erik, and Hunkeler, Priska
- Abstract
The polar oceans' sea ice cover is a challenging geophysical target to map. Current state of practice helicopter-electromagnetic (HEM) ice thickness mapping is limited to 1D interpretation due to common procedures and systems that are mainly sensitive to layered structures. We present a new generation Multi-sensor, Airborne Sea Ice Explorer (MAiSIE) to overcome these limitations. As the actual sea ice structure is 3D and in parts heterogeneous, errors up to 50% are observed due to the common 1D approximation. With MAiSIE we present a new EM concept based on one multi frequency transmitter loop and a three component receiver coil triplet without bucking The small weight frees additional payload to include a line scanner (lidar) and high accuracy INS/dGPS. The 3D surface topography from the scanner with the EM data at from 500 Hz to 8 kHz, in x, y, and z direction, will increase the accuracy of HEM derived pressure ridge geometry significantly. Experience from two field campaigns shows the proof-of-concept with acceptable sensor drift and receiver sensitivity. The preliminary 20 ppm noise level @ 4.1 kHz is sufficient to map level ice thickness with 10 cm precision for sensor altitudes below 13 m.
- Published
- 2013
245. A new web portal on sea ice for public and science - an example for an outreach activity within REKLIM
- Author
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Hiller, Wolfgang, Gerdes, Rüdiger, Treffeisen, Renate, Grosfeld, Klaus, Heygster, Georg, Asseng, Jölund, Nicolaus, Marcel, Hendricks, Stefan, Fritzsch, Bernadette, Bräuer, Benny, Weigelt, Marietta, and Kornmann, Aline
- Published
- 2013
246. Mass balance of sea ice in both hemispheres
- Author
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Hendricks, Stefan, Ricker, Robert, Helm, Veit, Schwegmann, Sandra, Haas, Christian, and Herber, Andreas
- Published
- 2013
247. Enhanced Sea-Ice Thickness Retrieval with Multi-Frequency Electromagnetic Devices
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Hunkeler, Priska, Hendricks, Stefan, Pfaffhuber, Andreas, Vöge, Malte, and Gerdes, Rüdiger
- Published
- 2013
248. Porosity of a sea-ice pressure ridge keel estimated on the basis of surface nuclear magnetic resonance measurements
- Author
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Rabenstein, Lasse, Nuber, Andre, Lehmann-Horn, Jochen, Hertrich, Marian, Hendricks, Stefan, Mahoney, Andy, and Eicken, Hajo
- Published
- 2013
249. On the qualification of available sea ice freeboard data for the validation of remote sensing observations
- Author
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Schwegmann, Sandra, Hendricks, Stefan, Ricker, Robert, Haas, Christian, and Herber, Andreas
- Abstract
The significant loss of Arctic sea ice during the last decades shows the sensitivity of the sea ice system to changes in the global climate. To distinguish between natural variability and the impact of global warming, an understanding of processes and feedbacks is necessary and for that, consistent and comprehensive measurements of the most important sea ice properties are required. While sea ice concentration is observed routinely year-round since the beginning of the satellite era, strategies to investigate the sea ice thickness distribution, crucially needed for an investigation of ice mass changes, has only recently been developed. To contribute to the interpretation of the remotely sensed sea ice thickness products, which are mainly based on freeboard determination from altimeter measurements, available airborne sea ice thickness and freeboard data have been collected within the Sea Ice Downstream Services for Arctic and Antarctic Users and Stakeholders (SIDARUS) EU-Project, and have been analyzed with respect to their usability for validation of the large scale satellite products. Thus, statistical parameters like the variability of freeboards within the common footprint areas of satellites have been analyzed from measurements made during the PAMARCMIP 2011 campaign to determine the differences between point measurements and areal averages. Also, impacts on the deviated sea ice thicknesses have been studied by means of a cross validation of freeboard-based sea ice thicknesses with airborne thickness measurements with electromagnetic induction sounding. Finally, since during the PAMARCMIP campaign few flights were performed in conjunction with CryoSat-2 overpasses, the airborne-based freeboards can finally be used for a comparison with satellite-derived data.
- Published
- 2012
250. Comparison Of Sea-Ice Freeboard And Thickness Distributions From Aircraft Data And Cryosat-2
- Author
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Ricker, Robert, Hendricks, Stefan, Helm, Veit, Gerdes, Rüdiger, and Skourup, Henriette
- Abstract
The only remote sensing technique capable of obtain- ing sea-ice thickness on basin-scale are satellite altime- ter missions, such as the 2010 launched CryoSat-2. It is equipped with a Ku-Band radar altimeter, which mea- sures the height of the ice surface above the sea level. This method requires highly accurate range measure- ments. During the CryoSat Validation Experiment (Cry- oVEx) 2011 in the Lincoln Sea, Cryosat-2 underpasses were accomplished with two aircraft, which carried an airborne laser-scanner, a radar altimeter and an electro- magnetic induction device for direct sea-ice thickness re- trieval. Both aircraft flew in close formation at the same time of a CryoSat-2 overpass. This is a study about the comparison of the sea-ice freeboard and thickness dis- tribution of airborne validation and CryoSat-2 measure- ments within the multi-year sea-ice region of the Lincoln Sea in spring, with respect to the penetration of the Ku- Band signal into the snow.
- Published
- 2012
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