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International audience ; Simulation of recent northern winter climate trends by greenhouse-gas forcing, Nature, 399, 452-455,1999. Thompson, D.WJ., and J. M.Wallace,Annular modes in the extratropical circulation, Part I, month-to-month variability./ Clim., PAGES 317,320 More than 40% of the marine heat flow data collected since the early experiments of Sir Edward Bullard in 1949 were obtained using shallow penetration probes less than 5 m long [Louden and Wright, 1989] .The common belief that these data are reliable enough to model deep-seated thermal processes is sup ported by a few experiments in which heat flow measurements made in the Deep Sea Drilling Program (DSDP) and the Ocean Drilling Pro gram (ODP) were compared to nearby surface heat flow measurements [e.g.,Hyndman etal, 1984]. However, thermal measurements made with 18-m penetrations recently collected on the northern flank of the SouthEast Indian Ridge (SEIR) bring a new perspective to this belief. In the study area, measurements of heat flow taken at the surface (0-5 m) and mea surements taken at greater depths (3-18 m) did not always concur. Investigating this lack of agreement will help address difficult ques tions about the interpretation of shallow pene tration (< 5 m) marine heat flow measurements. The data were obtained during the MD120-ANTAUS expedition carried out by R/V Marion Dufresne that was conducted from October 12 to November 7,2000 from Fremantle, Australia, to La Reunion Island.The primary objective of this cruise was to study marine heat flow vari ations along a 14-Ma isochron that parallels the SouthEast Indian Ridge (SEIR) between the Saint-Paul/Amsterdam hot spot and the Australian-Antarctic Discordance (AAD),an anomalously deep section of the Mid-Ocean Ridge that is often attributed to a mantle "cold spot." In the 1960s and 1970s, heat flow meas urements were obtained near the AAD as part of reconnaissance surveys [Von Herzen and Langseth, 1966; Langseth and Taylor, 1967; Anderson et al., 1977]. However, to interpret heat flow variations in this region of thin and patchy sediment cover, it is not only necessary to obtain more data, but to collect data that can be used to trace water circulation and dis criminate between the conductive and the convective components of the measured heat flow.To accomplish this, we collected long sediment cores, along with heat flow data to greater depths, to study the physical properties of the sediments and tentatively investigate the role of water circulation using helium isotopic ratios 3 He/ 4 He as tracers of hydrothermal activity. If water has circulated within the crust, then the 3 He/ 4 He isotopic signature is expected to be that of the crust and upper mantle; if water circulation has been confined to the sediment layer, it is expected to be that of the ocean and atmosphere. Despite rough weather and bad seas, a total of 25 thermal measurements was obtained using 9 autonomous digital temperature probes fitted on an 18-m-long, 13-cm-diameter gravity corer.Full penetration of 18 m was regularly achieved. Figure 2 shows examples of non-linear temperature gradients obtained at three differ ent sites. Each temperature measurement was systematically duplicated by two sensors that were spaced 64 mm apart. Hence, experimen tal effects cannot explain the observed non-linearity Tests performed onboard after recovery clearly preclude systematic errors due to prob lems with calibration or drift of a thermistor. The observed non-linearity, which is too important to be explained by variations in thermal conductivity, clearly results from the combination of two natural effects: vertical advection of water into the sediments and vari ations in bottom-water temperature. Advection of water affects the shape of the temperature versus depth curve: convex curvature indicates water flowing upward; concave curvature indi cates water flowing downward; a vertical gradi ent indicates the presence of an aquifer [e.g., Anderson et al., 1979]. Yearly variations in bot tom-water temperature affect the thermal gra dient in the first 3-4 m. Although further analysis is needed to determine the characteristics of the suspected bottom-water temperature changes, our results raise questions about the heat flow estimates that we would have obtained in this specific study area using shallow penetration probes of less than ~5 m. The above describes some advantages of combining coring and heat flow measurements within the sediments at great depths. R/V Marion Dufresne has the ability to take ultra-long cores of up to 60 m using a giant corer. Fig. 1. Temperature probes welded onto the gravity corer onboard R/V Marion Dufresne. Inset shows sketch of the autonomous temperature probe. R/V Marion Dufresne is a multipurpose , 130-m-long research and supply vessel that both provides logistics for the French austral islands and conducts oceanographic research. Specifically designed for very severe weather conditions, the ship allows full performance in rough seas. The vessel, which is equipped with the full suite of geophysical facilities, including a system for multi-beam bathymetry and imagery, can raise 60-m sediment cores. Facing an increasing scientific demand, the French government decided in 1999 to reduce the ship time devoted to logistical operations to 120 days per year and allow the French Polar Institute (IFRTP) to conduct research throughout the world for 245 days per year. This paves the road for new approaches and the development of integrated, multidisciplinary programs, as recently evidenced with the MD120-ANTAUS expedition.

International audience ; Simulation of recent northern winter climate trends by greenhouse-gas forcing, Nature, 399, 452-455,1999. Thompson, D.WJ., and J. M.Wallace,Annular modes in the extratropical circulation, Part I, month-to-month variability./ Clim., PAGES 317,320 More than 40% of the marine heat flow data collected since the early experiments of Sir Edward Bullard in 1949 were obtained using shallow penetration probes less than 5 m long [Louden and Wright, 1989] .The common belief that these data are reliable enough to model deep-seated thermal processes is sup ported by a few experiments in which heat flow measurements made in the Deep Sea Drilling Program (DSDP) and the Ocean Drilling Pro gram (ODP) were compared to nearby surface heat flow measurements [e.g.,Hyndman etal, 1984]. However, thermal measurements made with 18-m penetrations recently collected on the northern flank of the SouthEast Indian Ridge (SEIR) bring a new perspective to this belief. In the study area, measurements of heat flow taken at the surface (0-5 m) and mea surements taken at greater depths (3-18 m) did not always concur. Investigating this lack of agreement will help address difficult ques tions about the interpretation of shallow pene tration (< 5 m) marine heat flow measurements. The data were obtained during the MD120-ANTAUS expedition carried out by R/V Marion Dufresne that was conducted from October 12 to November 7,2000 from Fremantle, Australia, to La Reunion Island.The primary objective of this cruise was to study marine heat flow vari ations along a 14-Ma isochron that parallels the SouthEast Indian Ridge (SEIR) between the Saint-Paul/Amsterdam hot spot and the Australian-Antarctic Discordance (AAD),an anomalously deep section of the Mid-Ocean Ridge that is often attributed to a mantle "cold spot." In the 1960s and 1970s, heat flow meas urements were obtained near the AAD as part of reconnaissance surveys [Von Herzen and Langseth, 1966; Langseth and Taylor, 1967; Anderson et al., 1977]. However, to interpret heat flow variations in this region of thin and patchy sediment cover, it is not only necessary to obtain more data, but to collect data that can be used to trace water circulation and dis criminate between the conductive and the convective components of the measured heat flow.To accomplish this, we collected long sediment cores, along with heat flow data to greater depths, to study the physical properties of the sediments and tentatively investigate the role of water circulation using helium isotopic ratios 3 He/ 4 He as tracers of hydrothermal activity. If water has circulated within the crust, then the 3 He/ 4 He isotopic signature is expected to be that of the crust and upper mantle; if water circulation has been confined to the sediment layer, it is expected to be that of the ocean and atmosphere. Despite rough weather and bad seas, a total of 25 thermal measurements was obtained using 9 autonomous digital temperature probes fitted on an 18-m-long, 13-cm-diameter gravity corer.Full penetration of 18 m was regularly achieved. Figure 2 shows examples of non-linear temperature gradients obtained at three differ ent sites. Each temperature measurement was systematically duplicated by two sensors that were spaced 64 mm apart. Hence, experimen tal effects cannot explain the observed non-linearity Tests performed onboard after recovery clearly preclude systematic errors due to prob lems with calibration or drift of a thermistor. The observed non-linearity, which is too important to be explained by variations in thermal conductivity, clearly results from the combination of two natural effects: vertical advection of water into the sediments and vari ations in bottom-water temperature. Advection of water affects the shape of the temperature versus depth curve: convex curvature indicates water flowing upward; concave curvature indi cates water flowing downward; a vertical gradi ent indicates the presence of an aquifer [e.g., Anderson et al., 1979]. Yearly variations in bot tom-water temperature affect the thermal gra dient in the first 3-4 m. Although further analysis is needed to determine the characteristics of the suspected bottom-water temperature changes, our results raise questions about the heat flow estimates that we would have obtained in this specific study area using shallow penetration probes of less than ~5 m. The above describes some advantages of combining coring and heat flow measurements within the sediments at great depths. R/V Marion Dufresne has the ability to take ultra-long cores of up to 60 m using a giant corer. Fig. 1. Temperature probes welded onto the gravity corer onboard R/V Marion Dufresne. Inset shows sketch of the autonomous temperature probe. R/V Marion Dufresne is a multipurpose , 130-m-long research and supply vessel that both provides logistics for the French austral islands and conducts oceanographic research. Specifically designed for very severe weather conditions, the ship allows full performance in rough seas. The vessel, which is equipped with the full suite of geophysical facilities, including a system for multi-beam bathymetry and imagery, can raise 60-m sediment cores. Facing an increasing scientific demand, the French government decided in 1999 to reduce the ship time devoted to logistical operations to 120 days per year and allow the French Polar Institute (IFRTP) to conduct research throughout the world for 245 days per year. This paves the road for new approaches and the development of integrated, multidisciplinary programs, as recently evidenced with the MD120-ANTAUS expedition.

International audience ; Simulation of recent northern winter climate trends by greenhouse-gas forcing, Nature, 399, 452-455,1999. Thompson, D.WJ., and J. M.Wallace,Annular modes in the extratropical circulation, Part I, month-to-month variability./ Clim., PAGES 317,320 More than 40% of the marine heat flow data collected since the early experiments of Sir Edward Bullard in 1949 were obtained using shallow penetration probes less than 5 m long [Louden and Wright, 1989] .The common belief that these data are reliable enough to model deep-seated thermal processes is sup ported by a few experiments in which heat flow measurements made in the Deep Sea Drilling Program (DSDP) and the Ocean Drilling Pro gram (ODP) were compared to nearby surface heat flow measurements [e.g.,Hyndman etal, 1984]. However, thermal measurements made with 18-m penetrations recently collected on the northern flank of the SouthEast Indian Ridge (SEIR) bring a new perspective to this belief. In the study area, measurements of heat flow taken at the surface (0-5 m) and mea surements taken at greater depths (3-18 m) did not always concur. Investigating this lack of agreement will help address difficult ques tions about the interpretation of shallow pene tration (< 5 m) marine heat flow measurements. The data were obtained during the MD120-ANTAUS expedition carried out by R/V Marion Dufresne that was conducted from October 12 to November 7,2000 from Fremantle, Australia, to La Reunion Island.The primary objective of this cruise was to study marine heat flow vari ations along a 14-Ma isochron that parallels the SouthEast Indian Ridge (SEIR) between the Saint-Paul/Amsterdam hot spot and the Australian-Antarctic Discordance (AAD),an anomalously deep section of the Mid-Ocean Ridge that is often attributed to a mantle "cold spot." In the 1960s and 1970s, heat flow meas urements were obtained near the AAD as part of reconnaissance surveys [Von Herzen and Langseth, 1966; Langseth and Taylor, 1967; Anderson et al., 1977]. However, to interpret heat flow variations in this region of thin and patchy sediment cover, it is not only necessary to obtain more data, but to collect data that can be used to trace water circulation and dis criminate between the conductive and the convective components of the measured heat flow.To accomplish this, we collected long sediment cores, along with heat flow data to greater depths, to study the physical properties of the sediments and tentatively investigate the role of water circulation using helium isotopic ratios 3 He/ 4 He as tracers of hydrothermal activity. If water has circulated within the crust, then the 3 He/ 4 He isotopic signature is expected to be that of the crust and upper mantle; if water circulation has been confined to the sediment layer, it is expected to be that of the ocean and atmosphere. Despite rough weather and bad seas, a total of 25 thermal measurements was obtained using 9 autonomous digital temperature probes fitted on an 18-m-long, 13-cm-diameter gravity corer.Full penetration of 18 m was regularly achieved. Figure 2 shows examples of non-linear temperature gradients obtained at three differ ent sites. Each temperature measurement was systematically duplicated by two sensors that were spaced 64 mm apart. Hence, experimen tal effects cannot explain the observed non-linearity Tests performed onboard after recovery clearly preclude systematic errors due to prob lems with calibration or drift of a thermistor. The observed non-linearity, which is too important to be explained by variations in thermal conductivity, clearly results from the combination of two natural effects: vertical advection of water into the sediments and vari ations in bottom-water temperature. Advection of water affects the shape of the temperature versus depth curve: convex curvature indicates water flowing upward; concave curvature indi cates water flowing downward; a vertical gradi ent indicates the presence of an aquifer [e.g., Anderson et al., 1979]. Yearly variations in bot tom-water temperature affect the thermal gra dient in the first 3-4 m. Although further analysis is needed to determine the characteristics of the suspected bottom-water temperature changes, our results raise questions about the heat flow estimates that we would have obtained in this specific study area using shallow penetration probes of less than ~5 m. The above describes some advantages of combining coring and heat flow measurements within the sediments at great depths. R/V Marion Dufresne has the ability to take ultra-long cores of up to 60 m using a giant corer. Fig. 1. Temperature probes welded onto the gravity corer onboard R/V Marion Dufresne. Inset shows sketch of the autonomous temperature probe. R/V Marion Dufresne is a multipurpose , 130-m-long research and supply vessel that both provides logistics for the French austral islands and conducts oceanographic research. Specifically designed for very severe weather conditions, the ship allows full performance in rough seas. The vessel, which is equipped with the full suite of geophysical facilities, including a system for multi-beam bathymetry and imagery, can raise 60-m sediment cores. Facing an increasing scientific demand, the French government decided in 1999 to reduce the ship time devoted to logistical operations to 120 days per year and allow the French Polar Institute (IFRTP) to conduct research throughout the world for 245 days per year. This paves the road for new approaches and the development of integrated, multidisciplinary programs, as recently evidenced with the MD120-ANTAUS expedition.

International audience ; Simulation of recent northern winter climate trends by greenhouse-gas forcing, Nature, 399, 452-455,1999. Thompson, D.WJ., and J. M.Wallace,Annular modes in the extratropical circulation, Part I, month-to-month variability./ Clim., PAGES 317,320 More than 40% of the marine heat flow data collected since the early experiments of Sir Edward Bullard in 1949 were obtained using shallow penetration probes less than 5 m long [Louden and Wright, 1989] .The common belief that these data are reliable enough to model deep-seated thermal processes is sup ported by a few experiments in which heat flow measurements made in the Deep Sea Drilling Program (DSDP) and the Ocean Drilling Pro gram (ODP) were compared to nearby surface heat flow measurements [e.g.,Hyndman etal, 1984]. However, thermal measurements made with 18-m penetrations recently collected on the northern flank of the SouthEast Indian Ridge (SEIR) bring a new perspective to this belief. In the study area, measurements of heat flow taken at the surface (0-5 m) and mea surements taken at greater depths (3-18 m) did not always concur. Investigating this lack of agreement will help address difficult ques tions about the interpretation of shallow pene tration (< 5 m) marine heat flow measurements. The data were obtained during the MD120-ANTAUS expedition carried out by R/V Marion Dufresne that was conducted from October 12 to November 7,2000 from Fremantle, Australia, to La Reunion Island.The primary objective of this cruise was to study marine heat flow vari ations along a 14-Ma isochron that parallels the SouthEast Indian Ridge (SEIR) between the Saint-Paul/Amsterdam hot spot and the Australian-Antarctic Discordance (AAD),an anomalously deep section of the Mid-Ocean Ridge that is often attributed to a mantle "cold spot." In the 1960s and 1970s, heat flow meas urements were obtained near the AAD as part of reconnaissance surveys [Von Herzen and Langseth, 1966; Langseth and Taylor, 1967; Anderson et al., 1977]. However, to interpret heat flow variations in this region of thin and patchy sediment cover, it is not only necessary to obtain more data, but to collect data that can be used to trace water circulation and dis criminate between the conductive and the convective components of the measured heat flow.To accomplish this, we collected long sediment cores, along with heat flow data to greater depths, to study the physical properties of the sediments and tentatively investigate the role of water circulation using helium isotopic ratios 3 He/ 4 He as tracers of hydrothermal activity. If water has circulated within the crust, then the 3 He/ 4 He isotopic signature is expected to be that of the crust and upper mantle; if water circulation has been confined to the sediment layer, it is expected to be that of the ocean and atmosphere. Despite rough weather and bad seas, a total of 25 thermal measurements was obtained using 9 autonomous digital temperature probes fitted on an 18-m-long, 13-cm-diameter gravity corer.Full penetration of 18 m was regularly achieved. Figure 2 shows examples of non-linear temperature gradients obtained at three differ ent sites. Each temperature measurement was systematically duplicated by two sensors that were spaced 64 mm apart. Hence, experimen tal effects cannot explain the observed non-linearity Tests performed onboard after recovery clearly preclude systematic errors due to prob lems with calibration or drift of a thermistor. The observed non-linearity, which is too important to be explained by variations in thermal conductivity, clearly results from the combination of two natural effects: vertical advection of water into the sediments and vari ations in bottom-water temperature. Advection of water affects the shape of the temperature versus depth curve: convex curvature indicates water flowing upward; concave curvature indi cates water flowing downward; a vertical gradi ent indicates the presence of an aquifer [e.g., Anderson et al., 1979]. Yearly variations in bot tom-water temperature affect the thermal gra dient in the first 3-4 m. Although further analysis is needed to determine the characteristics of the suspected bottom-water temperature changes, our results raise questions about the heat flow estimates that we would have obtained in this specific study area using shallow penetration probes of less than ~5 m. The above describes some advantages of combining coring and heat flow measurements within the sediments at great depths. R/V Marion Dufresne has the ability to take ultra-long cores of up to 60 m using a giant corer. Fig. 1. Temperature probes welded onto the gravity corer onboard R/V Marion Dufresne. Inset shows sketch of the autonomous temperature probe. R/V Marion Dufresne is a multipurpose , 130-m-long research and supply vessel that both provides logistics for the French austral islands and conducts oceanographic research. Specifically designed for very severe weather conditions, the ship allows full performance in rough seas. The vessel, which is equipped with the full suite of geophysical facilities, including a system for multi-beam bathymetry and imagery, can raise 60-m sediment cores. Facing an increasing scientific demand, the French government decided in 1999 to reduce the ship time devoted to logistical operations to 120 days per year and allow the French Polar Institute (IFRTP) to conduct research throughout the world for 245 days per year. This paves the road for new approaches and the development of integrated, multidisciplinary programs, as recently evidenced with the MD120-ANTAUS expedition.

International audience ; Simulation of recent northern winter climate trends by greenhouse-gas forcing, Nature, 399, 452-455,1999. Thompson, D.WJ., and J. M.Wallace,Annular modes in the extratropical circulation, Part I, month-to-month variability./ Clim., PAGES 317,320 More than 40% of the marine heat flow data collected since the early experiments of Sir Edward Bullard in 1949 were obtained using shallow penetration probes less than 5 m long [Louden and Wright, 1989] .The common belief that these data are reliable enough to model deep-seated thermal processes is sup ported by a few experiments in which heat flow measurements made in the Deep Sea Drilling Program (DSDP) and the Ocean Drilling Pro gram (ODP) were compared to nearby surface heat flow measurements [e.g.,Hyndman etal, 1984]. However, thermal measurements made with 18-m penetrations recently collected on the northern flank of the SouthEast Indian Ridge (SEIR) bring a new perspective to this belief. In the study area, measurements of heat flow taken at the surface (0-5 m) and mea surements taken at greater depths (3-18 m) did not always concur. Investigating this lack of agreement will help address difficult ques tions about the interpretation of shallow pene tration (< 5 m) marine heat flow measurements. The data were obtained during the MD120-ANTAUS expedition carried out by R/V Marion Dufresne that was conducted from October 12 to November 7,2000 from Fremantle, Australia, to La Reunion Island.The primary objective of this cruise was to study marine heat flow vari ations along a 14-Ma isochron that parallels the SouthEast Indian Ridge (SEIR) between the Saint-Paul/Amsterdam hot spot and the Australian-Antarctic Discordance (AAD),an anomalously deep section of the Mid-Ocean Ridge that is often attributed to a mantle "cold spot." In the 1960s and 1970s, heat flow meas urements were obtained near the AAD as part of reconnaissance surveys [Von Herzen and Langseth, 1966; Langseth and Taylor, 1967; Anderson et al., 1977]. However, to interpret heat flow variations in this region of thin and patchy sediment cover, it is not only necessary to obtain more data, but to collect data that can be used to trace water circulation and dis criminate between the conductive and the convective components of the measured heat flow.To accomplish this, we collected long sediment cores, along with heat flow data to greater depths, to study the physical properties of the sediments and tentatively investigate the role of water circulation using helium isotopic ratios 3 He/ 4 He as tracers of hydrothermal activity. If water has circulated within the crust, then the 3 He/ 4 He isotopic signature is expected to be that of the crust and upper mantle; if water circulation has been confined to the sediment layer, it is expected to be that of the ocean and atmosphere. Despite rough weather and bad seas, a total of 25 thermal measurements was obtained using 9 autonomous digital temperature probes fitted on an 18-m-long, 13-cm-diameter gravity corer.Full penetration of 18 m was regularly achieved. Figure 2 shows examples of non-linear temperature gradients obtained at three differ ent sites. Each temperature measurement was systematically duplicated by two sensors that were spaced 64 mm apart. Hence, experimen tal effects cannot explain the observed non-linearity Tests performed onboard after recovery clearly preclude systematic errors due to prob lems with calibration or drift of a thermistor. The observed non-linearity, which is too important to be explained by variations in thermal conductivity, clearly results from the combination of two natural effects: vertical advection of water into the sediments and vari ations in bottom-water temperature. Advection of water affects the shape of the temperature versus depth curve: convex curvature indicates water flowing upward; concave curvature indi cates water flowing downward; a vertical gradi ent indicates the presence of an aquifer [e.g., Anderson et al., 1979]. Yearly variations in bot tom-water temperature affect the thermal gra dient in the first 3-4 m. Although further analysis is needed to determine the characteristics of the suspected bottom-water temperature changes, our results raise questions about the heat flow estimates that we would have obtained in this specific study area using shallow penetration probes of less than ~5 m. The above describes some advantages of combining coring and heat flow measurements within the sediments at great depths. R/V Marion Dufresne has the ability to take ultra-long cores of up to 60 m using a giant corer. Fig. 1. Temperature probes welded onto the gravity corer onboard R/V Marion Dufresne. Inset shows sketch of the autonomous temperature probe. R/V Marion Dufresne is a multipurpose , 130-m-long research and supply vessel that both provides logistics for the French austral islands and conducts oceanographic research. Specifically designed for very severe weather conditions, the ship allows full performance in rough seas. The vessel, which is equipped with the full suite of geophysical facilities, including a system for multi-beam bathymetry and imagery, can raise 60-m sediment cores. Facing an increasing scientific demand, the French government decided in 1999 to reduce the ship time devoted to logistical operations to 120 days per year and allow the French Polar Institute (IFRTP) to conduct research throughout the world for 245 days per year. This paves the road for new approaches and the development of integrated, multidisciplinary programs, as recently evidenced with the MD120-ANTAUS expedition.

International audience ; Simulation of recent northern winter climate trends by greenhouse-gas forcing, Nature, 399, 452-455,1999. Thompson, D.WJ., and J. M.Wallace,Annular modes in the extratropical circulation, Part I, month-to-month variability./ Clim., PAGES 317,320 More than 40% of the marine heat flow data collected since the early experiments of Sir Edward Bullard in 1949 were obtained using shallow penetration probes less than 5 m long [Louden and Wright, 1989] .The common belief that these data are reliable enough to model deep-seated thermal processes is sup ported by a few experiments in which heat flow measurements made in the Deep Sea Drilling Program (DSDP) and the Ocean Drilling Pro gram (ODP) were compared to nearby surface heat flow measurements [e.g.,Hyndman etal, 1984]. However, thermal measurements made with 18-m penetrations recently collected on the northern flank of the SouthEast Indian Ridge (SEIR) bring a new perspective to this belief. In the study area, measurements of heat flow taken at the surface (0-5 m) and mea surements taken at greater depths (3-18 m) did not always concur. Investigating this lack of agreement will help address difficult ques tions about the interpretation of shallow pene tration (< 5 m) marine heat flow measurements. The data were obtained during the MD120-ANTAUS expedition carried out by R/V Marion Dufresne that was conducted from October 12 to November 7,2000 from Fremantle, Australia, to La Reunion Island.The primary objective of this cruise was to study marine heat flow vari ations along a 14-Ma isochron that parallels the SouthEast Indian Ridge (SEIR) between the Saint-Paul/Amsterdam hot spot and the Australian-Antarctic Discordance (AAD),an anomalously deep section of the Mid-Ocean Ridge that is often attributed to a mantle "cold spot." In the 1960s and 1970s, heat flow meas urements were obtained near the AAD as part of reconnaissance surveys [Von Herzen and Langseth, 1966; Langseth and Taylor, 1967; Anderson et al., 1977]. However, to interpret heat flow variations in this region of thin and patchy sediment cover, it is not only necessary to obtain more data, but to collect data that can be used to trace water circulation and dis criminate between the conductive and the convective components of the measured heat flow.To accomplish this, we collected long sediment cores, along with heat flow data to greater depths, to study the physical properties of the sediments and tentatively investigate the role of water circulation using helium isotopic ratios 3 He/ 4 He as tracers of hydrothermal activity. If water has circulated within the crust, then the 3 He/ 4 He isotopic signature is expected to be that of the crust and upper mantle; if water circulation has been confined to the sediment layer, it is expected to be that of the ocean and atmosphere. Despite rough weather and bad seas, a total of 25 thermal measurements was obtained using 9 autonomous digital temperature probes fitted on an 18-m-long, 13-cm-diameter gravity corer.Full penetration of 18 m was regularly achieved. Figure 2 shows examples of non-linear temperature gradients obtained at three differ ent sites. Each temperature measurement was systematically duplicated by two sensors that were spaced 64 mm apart. Hence, experimen tal effects cannot explain the observed non-linearity Tests performed onboard after recovery clearly preclude systematic errors due to prob lems with calibration or drift of a thermistor. The observed non-linearity, which is too important to be explained by variations in thermal conductivity, clearly results from the combination of two natural effects: vertical advection of water into the sediments and vari ations in bottom-water temperature. Advection of water affects the shape of the temperature versus depth curve: convex curvature indicates water flowing upward; concave curvature indi cates water flowing downward; a vertical gradi ent indicates the presence of an aquifer [e.g., Anderson et al., 1979]. Yearly variations in bot tom-water temperature affect the thermal gra dient in the first 3-4 m. Although further analysis is needed to determine the characteristics of the suspected bottom-water temperature changes, our results raise questions about the heat flow estimates that we would have obtained in this specific study area using shallow penetration probes of less than ~5 m. The above describes some advantages of combining coring and heat flow measurements within the sediments at great depths. R/V Marion Dufresne has the ability to take ultra-long cores of up to 60 m using a giant corer. Fig. 1. Temperature probes welded onto the gravity corer onboard R/V Marion Dufresne. Inset shows sketch of the autonomous temperature probe. R/V Marion Dufresne is a multipurpose , 130-m-long research and supply vessel that both provides logistics for the French austral islands and conducts oceanographic research. Specifically designed for very severe weather conditions, the ship allows full performance in rough seas. The vessel, which is equipped with the full suite of geophysical facilities, including a system for multi-beam bathymetry and imagery, can raise 60-m sediment cores. Facing an increasing scientific demand, the French government decided in 1999 to reduce the ship time devoted to logistical operations to 120 days per year and allow the French Polar Institute (IFRTP) to conduct research throughout the world for 245 days per year. This paves the road for new approaches and the development of integrated, multidisciplinary programs, as recently evidenced with the MD120-ANTAUS expedition.