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Featured researches published by J. Otero.


Annals of Glaciology | 2004

Three-dimensional modelling of the dynamics of Johnsons Glacier, Livingston Island, Antarctica

Carlos Martín; Francisco Navarro; J. Otero; Maria L. Cuadrado; Maria I. Corcuera

Abstract A new three-dimensional finite-element model of the steady-state dynamics of temperate glaciers has been developed and applied to Johnsons Glacier, Livingston Island, Antarctica, with the aim of determining the velocity and stress fields for the present glacier configuration. It solves the full Stokes system of differential equations without recourse to simplifications such as those involved in the shallow-ice approximation. Rather high values of the stiffness parameter B (∼0.19–0.23MPaa1/3) are needed to match the observed ice surface velocities, although these results do not differ much from those found by other authors for temperate glaciers. Best-fit values of the coefficient k in the sliding law (*2.2–2.7 x 103m a–1MPa–2) are also of the same order of magnitude as those found by other authors. The results for velocities are satisfactory, though locally there exist significant discrepancies between computed and observed ice surface velocities, particularly for the vertical ones. This could be due to failures in the sliding law (in particular, the lack of information on water pressure), the use of an artificial down-edge boundary condition and the fact that bed deformation is not considered. For the whole glacier system, the driving stress is largely balanced by the basal drag (80% of the driving stress). Longitudinal stress gradients are only important in the divide areas and near the glacier terminus, while lateral drag is only important at both sides of the terminal zone.


Arctic, Antarctic, and Alpine Research | 2014

Ice Volume Estimates from Ground-Penetrating Radar Surveys, Wedel Jarlsberg Land Glaciers, Svalbard

Francisco Navarro; A. Martín-Español; J. J. Lapazaran; Mariusz Grabiec; J. Otero; Evgeny Vasilenko; Darek Puczko

Abstract We present ground-penetrating radar (GPR)—based volume calculations, with associated error estimates, for eight glaciers on Wedel Jarlsberg Land, southwestern Spitsbergen, Svalbard, and compare them with those obtained from volume-area scaling relationships. The volume estimates are based upon GPR ice-thickness data collected during the period 2004–2013. The total area and volume of the ensemble are 502.91 ± 18.60 km2 and 91.91 ± 3.12 km3, respectively. The individual areas, volumes, and average ice thickness lie within 0.37–140.99 km2, 0.01–31.98 km3, and 28–227 m, respectively, with a maximum recorded ice thickness of 619 ± 13 m on Austre Torellbreen. To estimate the ice volume of unsurveyed tributary glaciers, we combine polynomial cross-sections with a function providing the best fit to the measured ice thickness along the center line of a collection of 22 surveyed tributaries. For the time-to-depth conversion of GPR data, we test the use of a glacierwide constant radio-wave velocity chosen on the basis of local or regional common midpoint measurements, versus the use of distinct velocities for the firn, cold ice, and temperate ice layers, concluding that the corresponding volume calculations agree with each other within their error bounds.


Annals of Glaciology | 2013

Radio-echo sounding and ice volume estimates of western Nordenskiold Land glaciers, Svalbard

A. Martín-Español; E.V. Vasilenko; Francisco Navarro; J. Otero; J.J. Lapazaran; I. Lavrentiev; Yu. Ya. Macheret; F. Machío

Abstract As part of ongoing work to obtain a reliable estimate of the total ice volume of Svalbard glaciers and their potential contribution to sea-level rise, we present here volume calculations, with detailed error estimates, for ten glaciers on western Nordenskiöld Land, central Spitsbergen, Svalbard. The volume estimates are based upon a dense net of GPR-retrieved ice thickness data collected over several field campaigns spanning the period 1999-2012. The total area and volume of the ensemble are 116.06 ± 4.53 km2 and 10.439 ±0.373 km3, respectively, while the individual areas, volumes and average ice thickness lie within 2.6-50.4 km2, 0.08-5.54 km3 and 29-108 m, respectively. Volume/area scaling relationships overestimate the total volume of these glaciers by up to 35% with respect to our calculation. On the basis of the pattern of scattering in the radargrams, we also analyse the hydrothermal structure of these glaciers. Nine of the ten are polythermal, while only one is entirely cold.


Frontiers of Earth Science in China | 2017

Modeling the Controls on the Front Position of a Tidewater Glacier in Svalbard

J. Otero; Francisco Navarro; J. J. Lapazaran; Ethan Welty; Darek Puczko; Roman Finkelnburg

Calving is an important mass-loss process at ice sheet and marine-terminating glacier margins, but identifying and quantifying its principal driving mechanisms remains challenging. Hansbreen is a grounded tidewater glacier in southern Spitsbergen, Svalbard, with a rich history of field and remote sensing observations. The available data make this glacier suitable for evaluating mechanisms and controls on calving, some of which are considered in this paper. We use a full-Stokes thermomechanical 2D flow model (Elmer/Ice), paired with a crevasse-depth calving criterion, to estimate Hansbreen’s front position at a weekly time resolution. The basal sliding coefficient is re-calibrated every four weeks by solving an inverse model. We investigate the possible role of backpressure at the front (a function of ice melange concentration) and the depth of water filling crevasses by examining the model’s ability to reproduce the observed seasonal cycles of terminus advance and retreat. Our results suggest that the ice-melange pressure plays an important role in the seasonal advance and retreat of the ice front, and that the crevasse-depth calving criterion, when driven by modelled surface meltwater, closely replicates observed variations in terminus position. These results suggest that tidewater glacier behavior is influenced by both oceanic and atmospheric processes, and that neither of them should be ignored.


Pure and Applied Geophysics | 2015

Characterization of Cavities Using the GPR, LIDAR and GNSS Techniques

Miguel Angel Conejo-Martín; Tomás Ramón Herrero-Tejedor; J. J. Lapazaran; Enrique Pérez-Martín; J. Otero; J. F. Prieto; Jesus Velasco

The study of the many types of natural and manmade cavities in different parts of the world is important to the fields of geology, geophysics, engineering, architectures, agriculture, heritages and landscape. Ground-penetrating radar (GPR) is a noninvasive geodetection and geolocation technique suitable for accurately determining buried structures. This technique requires knowing the propagation velocity of electromagnetic waves (EM velocity) in the medium. We propose a method for calibrating the EM velocity using the integration of laser imaging detection and ranging (LIDAR) and GPR techniques using the Global Navigation Satellite System (GNSS) as support for geolocation. Once the EM velocity is known and the GPR profiles have been properly processed and migrated, they will also show the hidden cavities and the old hidden structures from the cellar. In this article, we present a complete study of the joint use of the GPR, LIDAR and GNSS techniques in the characterization of cavities. We apply this methodology to study underground cavities in a group of wine cellars located in Atauta (Soria, Spain). The results serve to identify construction elements that form the cavity and group of cavities or cellars. The described methodology could be applied to other shallow underground structures with surface connection, where LIDAR and GPR profiles could be joined, as, for example, in archaeological cavities, sewerage systems, drainpipes, etc.


Journal of Glaciology | 2010

A three-dimensional calving model: numerical experiments on Johnsons Glacier, Livingston Island, Antarctica

J. Otero; Francisco Navarro; Carlos Martín; Maria L. Cuadrado; Maria I. Corcuera


Journal of Glaciology | 2015

Estimate of the total volume of Svalbard glaciers, and their potential contribution to sea-level rise, using new regionally based scaling relationships

A. Martín-Español; Francisco Navarro; J. Otero; J. J. Lapazaran; M. Błaszczyk


The Cryosphere | 2012

Sensitivity of a distributed temperature-radiation index melt model based on AWS observations and surface energy balance fluxes, Hurd Peninsula glaciers, Livingston Island, Antarctica

U. Y. Jonsell; Francisco Navarro; M. Bañón; J. J. Lapazaran; J. Otero


Journal of Glaciology | 2016

On the errors involved in ice-thickness estimates I: Ground-penetrating radar measurement errors

J. J. Lapazaran; J. Otero; A. Martín-Español; Francisco Navarro


Journal of Glaciology | 2016

On the errors involved in ice-thickness estimates III: Error in volume

A. Martín-Español; J. J. Lapazaran; J. Otero; Francisco Navarro

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Francisco Navarro

Technical University of Madrid

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J. J. Lapazaran

Technical University of Madrid

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A. Martín-Español

Technical University of Madrid

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Francisco Machío

Pontifical University of Salamanca

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Carlos Martín

British Antarctic Survey

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Darek Puczko

Polish Academy of Sciences

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Enrique Pérez-Martín

Technical University of Madrid

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J. F. Prieto

Technical University of Madrid

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Jesus Velasco

Technical University of Madrid

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M. Bañón

Agencia Estatal de Meteorología

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