Stefano Gandolfi | Università di Bologna (original) (raw)

Papers by Stefano Gandolfi

VLNDEF (Victoria Land Network for DEFormationn control) Geodetic Program addresses the crustal de... more VLNDEF (Victoria Land Network for DEFormationn control) Geodetic Program addresses the crustal deformation control of the Northern Victoria Land (Antarctica) by means of geodetic GPS measurements. The project is within the activity of GIANT (Geodetic Infrastructure of Antarctica) SCAR Program and was established within the actions of ANTEC (ANTarctic NeoTECtonics) Group of Specialists. During 1999-2000 and 2000-2001 Italian expeditions a

VLNDEF (Victoria Land Network for DEFormation control) project started in 1999 with the aim to me... more VLNDEF (Victoria Land Network for DEFormation control) project started in 1999 with the aim to measure a network for the study of regional geodynamics of northern Victoria Land. In 1999-2000 and 2000-01 italian expeditions, a network of 25 stations with an average distance of 70 km covering the area from Terra Nova Bay, italian sta- tion in Antarctica, to the northern Oates Coast on Pacific ocean, about 700 km long and about 300 km large, was established and surveyed. The network design and stations location were based on principal faults of the area pointed out by most recent tecton- ics studies. The research activity is made within GIANT (Geodetic Infrastructure of ANTarctica) program and ANTEC (ANtarctic neoTECtonics) Group of Specialists of SCAR (Scientific Committee on Antarctic Research).The network coordinates are de- fined in most recent ITRF 2000 system through the emanation from GPS permanent station TNB1. TNB1 was included in SCAR GPS Epoch measurements campaigns and, con...

Surface mass balance distribution and its temporal and spatial variability is an input parameter ... more Surface mass balance distribution and its temporal and spatial variability is an input parameter in mass balance studies. It also has important implications for palaeoclimatic series from ice cores. Different methods were adopted, compared and integrated (stake farm, core analysis, snow radar, surface morphology, remote sensing) at eight sites along a transept from Terra Nova Bay to Dome C (East Antarctica). Cores were linked by snow radar and GPS surveys to provide detailed information on spatial variability in surface mass balance. Thirty-nine cores were dated by identifying tritium/β marker levels (1965-66) and nssSO4 2- spikes of Tambora and Unknown volcanic events (1816 - 1810) in order to provide information on temporal variability. Spatial variability measurements show that maximum snow accumulation is strictly correlated to firn temperature and that it is homogenous at macro-scales (hundreds of km2). Wind-driven sublimation processes, controlled by surface slope in the wind ...

Journal of Geophysical Research, 2002

Journal of Geodynamics, 2005

The paper discusses the long time series analysis of GPS permanent station located at Terra Nova ... more The paper discusses the long time series analysis of GPS permanent station located at Terra Nova Bay, East Antarctica (Victoria Land). The station (TNB1) was monumented during the 1997-1998 Italian expedition in Antarctica and the data collection started on January 1998. TNB1 is included in the Victoria Land network for deformation control (VLNDEF) network that was established with the aim to study the horizontal and vertical displacements in the region. The good-quality data obtained from this station allow the computation of long time series performed both by using a network approach with Bernese V4.2, and precise point positioning technique with GIPSY-OASIS II. In a first step, a subset of data was analysed to define the best processing strategy. Moreover, in the network approach, international GPS service (IGS) permanent stations (intra-and extra-plate) were used. Results obtained from the two approaches are comparable in terms of both repeatability and linear trend. Finally, velocities estimated for all Antarctic stations were compared to the values provided by ITRF2000. In most cases horizontal velocities agree with the model, while significant differences are present along the vertical components.

Global and Planetary Change, 2008

Ice divide-dome behaviour is used for ice sheet mass balance studies and interpretation of ice co... more Ice divide-dome behaviour is used for ice sheet mass balance studies and interpretation of ice core records. In order to characterize the historical behaviour (last 400 yr) of Dome C and Talos Dome (East Antarctica), ice velocities have been measured since 1996 using a GPS system, and the palaeo-spatial variability of snow accumulation has been surveyed using snow radar and firn cores. The snow accumulation distribution of both domes indicates distributions of accumulation that are non-symmetrical in relation to dome morphology. Changes in spatial distributions have been observed over the last few centuries, with a decrease in snow accumulation gradient along the wind direction at Talos Dome and a counterclockwise rotation of accumulation distribution in the northern part of Dome C. Observations at Dome C reveal a significant increase in accumulation since the 1950s, which could correlate to altered snow accumulation patterns due to changes in snowfall trajectory. Snow accumulation mechanisms are different at the two domes: a wind-driven snow accumulation process operates at Talos Dome, whereas snowfall trajectory direction is the main factor at Dome C. Repeated GPS measurements made at Talos Dome have highlighted changes in ice velocity, with a deceleration in the NE portion, acceleration in the SW portion and migration of dome summit, which are apparently correlated with changes in accumulation distribution. The observed behaviour in accumulation and velocity indicates that even the most remote areas of East Antarctica have changed from a decadal to secular scale.

Global and Planetary Change, 2008

In order to make inferences on the geodynamics of Antarctica, geodetic and gravimetric maps deriv... more In order to make inferences on the geodynamics of Antarctica, geodetic and gravimetric maps derived from past and new observations can be used. This paper provides new insights into the geodynamics of Antarctica by integrating data at regional and continental scales. In particular, signatures of geodynamic activity at a regional extent have been investigated in Victoria Land (VL, Antarctica) by means of Global Navigation Satellite System (GNSS) permanent station observations, data from the VLNDEF (Victoria Land Network for Deformation control) discontinuous network, and gravity station measurements. At the continental scale, episodic GNSS observations on VLNDEF sites collected for 20 years, together with continuous data from the International GNSS Service (IGS) and Polar Earth Observing Network (POLENET) sites, were processed, and the Euler pole position assessed with the angular velocity of the Antarctic plate. Both the Bouguer and the free-air gravity anomaly maps were obtained by integrating the available open-access geophysics dataset, and a compilation of 180 gravity measurements collected in the VL within the Italian National Program for Antarctic Research (PNRA) activities. As a result, new evidence has been detected at regional and continental scale. The main absolute motion of VL is towards SE (Ve 9.9 ± 0.26 mm/yr, Vn −11.9 ± 0.27 mm/yr) with a pattern similar to the transforms of the Tasman and Balleny fracture zones produced as consequence of Southern Ocean spreading. Residual velocities of the GNSS stations located in VL confirm the active role of the two main tectonic lineaments of the region, the Rennick-Aviator and the Lillie-Tucker faults with right-lateral sense of shear. The resulting VL gravity anomalies show a NW region characterized by small sized Bouguer anomaly with high uplift rates associated and a SE region with low values of Bouguer anomaly and general subsidence phenomena. The East and West Antarctica are characterized by a different thickness of the Earth's crust, and the relative velocities obtained by the observed GNSS data confirm that movements between the two regions are negligible. In East Antarctica, the roots of the main subglacial highlands, Gamburtsev Mts and Dronning Maud Land, are present. The Northern Victoria Land (NVL) is characterized by more scattered anomalies. These confirm the differences between the Glacial Isostatic Adjustment (GIA) modeled and observed uplift rates that could be related to deep-seated, regional scale structures.

Earth and Planetary Science Letters, 2001

Early geophysical studies hypothesized a continental rift structure beneath the Wilkes Subglacial... more Early geophysical studies hypothesized a continental rift structure beneath the Wilkes Subglacial Basin. Recent models favour a flexural origin for the basin linked to Transantarctic Mountains uplift and to East Antarctic Craton lithospheric rigidity. Flexural modelling predicts crustal ...

Annals of Glaciology, 2002

As part of the International Trans-Antarctic Scientific Expedition project, the Italian Antarctic... more As part of the International Trans-Antarctic Scientific Expedition project, the Italian Antarctic Programme undertook two traverses from the Terra Nova station to Talos Dome and to Dome C. Along the traverses, the party carried out several tasks (drilling, glaciological and geophysical exploration). The difference in spectral response between glazed surfaces and snow makes it simple to identify these areas on visible/near-infrared satellite images. Integration of field observation and remotely sensed data allows the description of different mega-morphologic features: wide glazed surfaces, sastrugi glazed surface fields, transverse dunes and megadunes. Topography global positioning system, ground penetrating radar and detailed snow-surface surveys have been carried out, providing new information about the formation and evolution of mega-morphologic features. The extensive presence, (up to 30%) of glazed surface caused by a long hiatus in accumulation, with an accumulation rate of nil...

Annals of Glaciology, 2004

Talos Dome is an ice dome on the edge of the East Antarctic plateau; because accumulation is high... more Talos Dome is an ice dome on the edge of the East Antarctic plateau; because accumulation is higher here than in other domes of East Antarctica, the ice preserves a good geochemical and palaeoclimatic record. A new map of the Talos Dome area locates the dome summit using the global positioning system (GPS) (72˚47’ 14’’S, 159˚04’ 2’’ E; 2318.5m elevation (WGS84)). A surface strain network of nine stakes was measured using GPS. Data indicate that the stake closest to the summit moves south-southeast at a few cm a–1. The other stakes, located 8 km away, move up to 0.33ma–1. Airborne radar measurements indicate that the bedrock at the Talos Dome summit is about 400m in elevation, and that it is covered by about 1900 m of ice. Snow radar and GPS surveys show that internal layering is continuous and horizontal in the summit area (15 km radius). The depth distribution analysis of snow radar layers reveals that accumulation decreases downwind of the dome (north-northeast) and increases upwi...

Annals of Glaciology, 2004

Dome C was chosen by the European Project for Ice Coring in Antarctica (EPICA) as the site for th... more Dome C was chosen by the European Project for Ice Coring in Antarctica (EPICA) as the site for the drilling of a deep ice core. This paper presents results from geodetic surveys of ice velocities (absolute and relative) at Dome C and along a transect to Terra Nova Bay. The purpose of the surveys was to provide accurate data for the study of ice dynamics, particularly a strain network comprising 37 poles surveyed in 1995 and again in 1999. Data indicate that the ice surface at the poles closest to the topographic summit moves horizontally by up to a few mm a–1 in a direction consistent with downslope motion of the ice sheet, while 25 km from the summit it moves up to 211 mma–1. The EPICA drilling site yields an interpolated velocity of about 15 ±10mma–1 in a north-northwesterly direction. Analysis of the velocity field and surface topography reveals that the surface flow centre is nearly co-located with the dome summit, and that both are in a steady-state condition. The measured hori...

Annals of Glaciology, 2000

A new plano-altimetric map of the Dome Concordia (Dome C) area was drawn up from 1995/96 kinemati... more A new plano-altimetric map of the Dome Concordia (Dome C) area was drawn up from 1995/96 kinematic double-frequency global-positioning-system (GPS) data of two different projects, as well as static GPS data from a geodetic net for deformation analysis and ice-flow velocity measurements covering an area of about 2000 km2.The GPS surveys were carried out for EPICA during the 10th and 11th Italian Expeditions to choose the optimal location for deep ice-core drilling at Dome C. The accuracy of the kinematic survey was tested by analysing the height-value differences at intersections between different profiles; values ranged from 50–150 mm.The new map was compared with the 1993 kinematic interferential GPS data and residuals between the 1993 and 1995 data were calculated. The surface topographic values were used to calculate the elevation of the Dome C area bedrock, obtained from the reference ground-based and airborne radio-echo-sounding surveys.

Journal of Cultural Heritage, 2002

Started in 1996, the Chacas Valley Project is coordinated by Laura Laurencich Minelli and aims to... more Started in 1996, the Chacas Valley Project is coordinated by Laura Laurencich Minelli and aims to study the social-cultural organization of space in the Chacas Region (Ancash-Perú) during the Early Intermediate Period (III-VII century A.D.). For an anthropological interpretation of ancient urbanized territory, a multidisciplinary approach focused on gathering both archeological data and topographical information is necessary. The kinematic GPS method has been applied in order to reach the needed accuracy in representing the geometric properties of the objects, to preserve the geometric properties between the structures and to document the relations with the ground morphological aspects.

International Association of Geodesy Symposia, 2001

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2013

VLNDEF (Victoria Land Network for DEFormationn control) Geodetic Program addresses the crustal de... more VLNDEF (Victoria Land Network for DEFormationn control) Geodetic Program addresses the crustal deformation control of the Northern Victoria Land (Antarctica) by means of geodetic GPS measurements. The project is within the activity of GIANT (Geodetic Infrastructure of Antarctica) SCAR Program and was established within the actions of ANTEC (ANTarctic NeoTECtonics) Group of Specialists. During 1999-2000 and 2000-2001 Italian expeditions a

VLNDEF (Victoria Land Network for DEFormation control) project started in 1999 with the aim to me... more VLNDEF (Victoria Land Network for DEFormation control) project started in 1999 with the aim to measure a network for the study of regional geodynamics of northern Victoria Land. In 1999-2000 and 2000-01 italian expeditions, a network of 25 stations with an average distance of 70 km covering the area from Terra Nova Bay, italian sta- tion in Antarctica, to the northern Oates Coast on Pacific ocean, about 700 km long and about 300 km large, was established and surveyed. The network design and stations location were based on principal faults of the area pointed out by most recent tecton- ics studies. The research activity is made within GIANT (Geodetic Infrastructure of ANTarctica) program and ANTEC (ANtarctic neoTECtonics) Group of Specialists of SCAR (Scientific Committee on Antarctic Research).The network coordinates are de- fined in most recent ITRF 2000 system through the emanation from GPS permanent station TNB1. TNB1 was included in SCAR GPS Epoch measurements campaigns and, con...

Surface mass balance distribution and its temporal and spatial variability is an input parameter ... more Surface mass balance distribution and its temporal and spatial variability is an input parameter in mass balance studies. It also has important implications for palaeoclimatic series from ice cores. Different methods were adopted, compared and integrated (stake farm, core analysis, snow radar, surface morphology, remote sensing) at eight sites along a transept from Terra Nova Bay to Dome C (East Antarctica). Cores were linked by snow radar and GPS surveys to provide detailed information on spatial variability in surface mass balance. Thirty-nine cores were dated by identifying tritium/β marker levels (1965-66) and nssSO4 2- spikes of Tambora and Unknown volcanic events (1816 - 1810) in order to provide information on temporal variability. Spatial variability measurements show that maximum snow accumulation is strictly correlated to firn temperature and that it is homogenous at macro-scales (hundreds of km2). Wind-driven sublimation processes, controlled by surface slope in the wind ...

Journal of Geophysical Research, 2002

Journal of Geodynamics, 2005

The paper discusses the long time series analysis of GPS permanent station located at Terra Nova ... more The paper discusses the long time series analysis of GPS permanent station located at Terra Nova Bay, East Antarctica (Victoria Land). The station (TNB1) was monumented during the 1997-1998 Italian expedition in Antarctica and the data collection started on January 1998. TNB1 is included in the Victoria Land network for deformation control (VLNDEF) network that was established with the aim to study the horizontal and vertical displacements in the region. The good-quality data obtained from this station allow the computation of long time series performed both by using a network approach with Bernese V4.2, and precise point positioning technique with GIPSY-OASIS II. In a first step, a subset of data was analysed to define the best processing strategy. Moreover, in the network approach, international GPS service (IGS) permanent stations (intra-and extra-plate) were used. Results obtained from the two approaches are comparable in terms of both repeatability and linear trend. Finally, velocities estimated for all Antarctic stations were compared to the values provided by ITRF2000. In most cases horizontal velocities agree with the model, while significant differences are present along the vertical components.

Global and Planetary Change, 2008

Ice divide-dome behaviour is used for ice sheet mass balance studies and interpretation of ice co... more Ice divide-dome behaviour is used for ice sheet mass balance studies and interpretation of ice core records. In order to characterize the historical behaviour (last 400 yr) of Dome C and Talos Dome (East Antarctica), ice velocities have been measured since 1996 using a GPS system, and the palaeo-spatial variability of snow accumulation has been surveyed using snow radar and firn cores. The snow accumulation distribution of both domes indicates distributions of accumulation that are non-symmetrical in relation to dome morphology. Changes in spatial distributions have been observed over the last few centuries, with a decrease in snow accumulation gradient along the wind direction at Talos Dome and a counterclockwise rotation of accumulation distribution in the northern part of Dome C. Observations at Dome C reveal a significant increase in accumulation since the 1950s, which could correlate to altered snow accumulation patterns due to changes in snowfall trajectory. Snow accumulation mechanisms are different at the two domes: a wind-driven snow accumulation process operates at Talos Dome, whereas snowfall trajectory direction is the main factor at Dome C. Repeated GPS measurements made at Talos Dome have highlighted changes in ice velocity, with a deceleration in the NE portion, acceleration in the SW portion and migration of dome summit, which are apparently correlated with changes in accumulation distribution. The observed behaviour in accumulation and velocity indicates that even the most remote areas of East Antarctica have changed from a decadal to secular scale.

Global and Planetary Change, 2008

In order to make inferences on the geodynamics of Antarctica, geodetic and gravimetric maps deriv... more In order to make inferences on the geodynamics of Antarctica, geodetic and gravimetric maps derived from past and new observations can be used. This paper provides new insights into the geodynamics of Antarctica by integrating data at regional and continental scales. In particular, signatures of geodynamic activity at a regional extent have been investigated in Victoria Land (VL, Antarctica) by means of Global Navigation Satellite System (GNSS) permanent station observations, data from the VLNDEF (Victoria Land Network for Deformation control) discontinuous network, and gravity station measurements. At the continental scale, episodic GNSS observations on VLNDEF sites collected for 20 years, together with continuous data from the International GNSS Service (IGS) and Polar Earth Observing Network (POLENET) sites, were processed, and the Euler pole position assessed with the angular velocity of the Antarctic plate. Both the Bouguer and the free-air gravity anomaly maps were obtained by integrating the available open-access geophysics dataset, and a compilation of 180 gravity measurements collected in the VL within the Italian National Program for Antarctic Research (PNRA) activities. As a result, new evidence has been detected at regional and continental scale. The main absolute motion of VL is towards SE (Ve 9.9 ± 0.26 mm/yr, Vn −11.9 ± 0.27 mm/yr) with a pattern similar to the transforms of the Tasman and Balleny fracture zones produced as consequence of Southern Ocean spreading. Residual velocities of the GNSS stations located in VL confirm the active role of the two main tectonic lineaments of the region, the Rennick-Aviator and the Lillie-Tucker faults with right-lateral sense of shear. The resulting VL gravity anomalies show a NW region characterized by small sized Bouguer anomaly with high uplift rates associated and a SE region with low values of Bouguer anomaly and general subsidence phenomena. The East and West Antarctica are characterized by a different thickness of the Earth's crust, and the relative velocities obtained by the observed GNSS data confirm that movements between the two regions are negligible. In East Antarctica, the roots of the main subglacial highlands, Gamburtsev Mts and Dronning Maud Land, are present. The Northern Victoria Land (NVL) is characterized by more scattered anomalies. These confirm the differences between the Glacial Isostatic Adjustment (GIA) modeled and observed uplift rates that could be related to deep-seated, regional scale structures.

Earth and Planetary Science Letters, 2001

Early geophysical studies hypothesized a continental rift structure beneath the Wilkes Subglacial... more Early geophysical studies hypothesized a continental rift structure beneath the Wilkes Subglacial Basin. Recent models favour a flexural origin for the basin linked to Transantarctic Mountains uplift and to East Antarctic Craton lithospheric rigidity. Flexural modelling predicts crustal ...

Annals of Glaciology, 2002

As part of the International Trans-Antarctic Scientific Expedition project, the Italian Antarctic... more As part of the International Trans-Antarctic Scientific Expedition project, the Italian Antarctic Programme undertook two traverses from the Terra Nova station to Talos Dome and to Dome C. Along the traverses, the party carried out several tasks (drilling, glaciological and geophysical exploration). The difference in spectral response between glazed surfaces and snow makes it simple to identify these areas on visible/near-infrared satellite images. Integration of field observation and remotely sensed data allows the description of different mega-morphologic features: wide glazed surfaces, sastrugi glazed surface fields, transverse dunes and megadunes. Topography global positioning system, ground penetrating radar and detailed snow-surface surveys have been carried out, providing new information about the formation and evolution of mega-morphologic features. The extensive presence, (up to 30%) of glazed surface caused by a long hiatus in accumulation, with an accumulation rate of nil...

Annals of Glaciology, 2004

Talos Dome is an ice dome on the edge of the East Antarctic plateau; because accumulation is high... more Talos Dome is an ice dome on the edge of the East Antarctic plateau; because accumulation is higher here than in other domes of East Antarctica, the ice preserves a good geochemical and palaeoclimatic record. A new map of the Talos Dome area locates the dome summit using the global positioning system (GPS) (72˚47’ 14’’S, 159˚04’ 2’’ E; 2318.5m elevation (WGS84)). A surface strain network of nine stakes was measured using GPS. Data indicate that the stake closest to the summit moves south-southeast at a few cm a–1. The other stakes, located 8 km away, move up to 0.33ma–1. Airborne radar measurements indicate that the bedrock at the Talos Dome summit is about 400m in elevation, and that it is covered by about 1900 m of ice. Snow radar and GPS surveys show that internal layering is continuous and horizontal in the summit area (15 km radius). The depth distribution analysis of snow radar layers reveals that accumulation decreases downwind of the dome (north-northeast) and increases upwi...

Annals of Glaciology, 2004

Dome C was chosen by the European Project for Ice Coring in Antarctica (EPICA) as the site for th... more Dome C was chosen by the European Project for Ice Coring in Antarctica (EPICA) as the site for the drilling of a deep ice core. This paper presents results from geodetic surveys of ice velocities (absolute and relative) at Dome C and along a transect to Terra Nova Bay. The purpose of the surveys was to provide accurate data for the study of ice dynamics, particularly a strain network comprising 37 poles surveyed in 1995 and again in 1999. Data indicate that the ice surface at the poles closest to the topographic summit moves horizontally by up to a few mm a–1 in a direction consistent with downslope motion of the ice sheet, while 25 km from the summit it moves up to 211 mma–1. The EPICA drilling site yields an interpolated velocity of about 15 ±10mma–1 in a north-northwesterly direction. Analysis of the velocity field and surface topography reveals that the surface flow centre is nearly co-located with the dome summit, and that both are in a steady-state condition. The measured hori...

Annals of Glaciology, 2000

A new plano-altimetric map of the Dome Concordia (Dome C) area was drawn up from 1995/96 kinemati... more A new plano-altimetric map of the Dome Concordia (Dome C) area was drawn up from 1995/96 kinematic double-frequency global-positioning-system (GPS) data of two different projects, as well as static GPS data from a geodetic net for deformation analysis and ice-flow velocity measurements covering an area of about 2000 km2.The GPS surveys were carried out for EPICA during the 10th and 11th Italian Expeditions to choose the optimal location for deep ice-core drilling at Dome C. The accuracy of the kinematic survey was tested by analysing the height-value differences at intersections between different profiles; values ranged from 50–150 mm.The new map was compared with the 1993 kinematic interferential GPS data and residuals between the 1993 and 1995 data were calculated. The surface topographic values were used to calculate the elevation of the Dome C area bedrock, obtained from the reference ground-based and airborne radio-echo-sounding surveys.

Journal of Cultural Heritage, 2002

Started in 1996, the Chacas Valley Project is coordinated by Laura Laurencich Minelli and aims to... more Started in 1996, the Chacas Valley Project is coordinated by Laura Laurencich Minelli and aims to study the social-cultural organization of space in the Chacas Region (Ancash-Perú) during the Early Intermediate Period (III-VII century A.D.). For an anthropological interpretation of ancient urbanized territory, a multidisciplinary approach focused on gathering both archeological data and topographical information is necessary. The kinematic GPS method has been applied in order to reach the needed accuracy in representing the geometric properties of the objects, to preserve the geometric properties between the structures and to document the relations with the ground morphological aspects.

International Association of Geodesy Symposia, 2001

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2013