Belen Martrat | CSIC (Consejo Superior de Investigaciones Científicas-Spanish National Research Council) (original) (raw)
Papers by Belen Martrat
Quality-control dashboards for North American records
Quality-control dashboards, Africa
Quality-control dashboards, for records from Antarctica
in GitHub Markdown format
This study analyzes coccolithophore abundance fluctuations (e.g., Emiliania huxleyi, Gephyrocapsa... more This study analyzes coccolithophore abundance fluctuations (e.g., Emiliania huxleyi, Gephyrocapsa specimens, and Florisphaera profunda) in core MD01-2444 sediment strata retrieved at the Iberian Margin, northeastern Atlantic Ocean. Coccolithophores are calcareous nannofossils, a major component of the oceanic phytoplankton, which provide information about past ecological and climatological variability. Results are supported by data on fossil organic compounds (sea surface temperatures, alkenones, and n-hexacosan-1-ol index) and geochemical analyses (benthic d13Ccc and planktonic d18Occ isotopes). Three scenarios are taken into account for this location at centennial-scale resolution over the last 70,000 years: the Holocene and the stadial and interstadial modes. The different alternatives are described by means of elements such as nutrients; upwelling phenomena; temperatures at surface and subsurface level; or the arrival of surface turbid, fresh, and cold waters due to icebergs, low sea level, increased aridity, and dust. During the Holocene, moderate primary productivity was observed (mainly concentrated in E. huxleyi specimens); surface temperatures were at maxima while the water column was highly ventilated by northern-sourced polar deep waters and warmer subsurface, nutrient-poor subtropical waters. Over most of the last glacial stadials, surface productivity weakened (higher F. profunda and reworked specimen percentages and lower diunsaturated and triunsaturated C37 alkenones); the arrival of cold Arctic surface waters traced by tetraunsaturated C37 peaks and large E. huxleyi, together with powerful ventilated southern-sourced polar deep waters, disturbed, in all likelihood, the delicate vertical equilibrium while preventing significant upwelling mixing. Finally, during the last glacial interstadials (lower F. profunda percentages, nonreworked material, and higher diunsaturated and triunsaturated C37 alkenones) a combined signal is observed: warm surface temperatures were concurrent with generally low oxyge [...]
Research is organised as a linked network of well-defined projects and targeted manuscripts, iden... more Research is organised as a linked network of well-defined projects and targeted manuscripts, identified and led by 2k members. This bottom-up concept of projects initiated and conducted by community members will further stimulate collaboration during Phase 3 of the 2k Network. PAGES 2k projects focus on specific scientific questions aligned with Phase 3 Themes, rather than being defined along regional boundaries. An enduring element from earlier phases is a culture of collegiality, transparency, and reciprocity. Phase 3 seeks to stimulate community-based projects and facilitate collaborations between researchers from different regions and career stages, drawing on the breadth, depth, broad expertise and input of the global PAGES 2k community. All PAGES 2k projects also promote best practises in Data Stewardship for the research community. Phase 3 seek to further develop collaborations with other research communities and engage with stakeholders at the project and network level through interaction with related institutions and initiatives such as Future Earth, WCRP, IPCC and EarthCube.
During the PROMESS campaign (summer 2004) a borehole (PRGL1) was drilled in the upper slope of th... more During the PROMESS campaign (summer 2004) a borehole (PRGL1) was drilled in the upper slope of the Gulf of Lions. Previous studies showed that the deposition of the sedimentary units at borehole PRGL1 was determined by changes in the discharge of the Rhone river, induced by sea level and climate variability with a strong 100 ka imprint. However, there are no detailed studies that focus on the glacial/interglacial transitions (i.e. Terminations) that define 100 ka Quaternary ice-age cycles. Here we present a high-resolution record of terrestrial long chain n-alkanes (C21 to C33) from MIS 3 to MIS 11 in order to monitor changes in the sediments deposited on the upper slope of the Gulf of Lions with the aim to provide new insight into the climatic events occurring during Terminations in the western Mediterranean Sea.Principal component analysis grouped n-alkane on the basis of the degree of maturation of organic matter (fresh/degraded) that allowed to monitor past variability in the source of the sediment deposited in the upper slope as a consequence of sea level and climate change. This information was used to estimate the impact that northern ice-sheet variability had on the western Mediterranean basin. As sea level started to fall, fresh terrestrial organic matter increased owing to the seaward migration of Rhone's mouth. Simultaneously, the decrease in sea level exposed old and reworked organic material from the Rhone's catchment, including the delta plain and the continental shelf, that was eroded and transported into our study site. This resulted in an increase in the proportion of degraded terrestrial organic matter together with sea level decrease. Aside from sea level changes, the proportion of fresh vs degraded organic matter seems to be affected by the amount of continental runoff, with an increasing proportion of fresh terrestrial organic matter occurring at times of reduced continental runoff. During the last glacial, the increase of fresh terrestrial organic matter was contemporaneous with Heinrich eve [...]
<p>The past two thousand years is a key interval for climate science. This period encompass... more <p>The past two thousand years is a key interval for climate science. This period encompasses both the era of human-induced global warming and a much longer interval when changes in Earth’s climate were governed principally by natural drivers and unforced variability. Since 2009, the Past Global Changes (PAGES) 2k Network has brought together hundreds of scientists from around the world to reconstruct and understand the climate of the Common Era using open and collaborative approaches to palaeoclimate science, including virtual meetings. The third phase of the network will end in December 2021. Here we highlight some key outputs of PAGES 2k and present the major themes and scientific questions emerging from recent surveys of the community. We explore how these might boost a new phase of PAGES 2k or a successor project(s). This year we will further reach out to the community through Town Hall consultations, vEGU and other meetings, and a PAGES 2k global webinar series. The aim of these activities is to foster development of post-2021 community-led PAGES initiatives that connect past and present climate.</p>
We compare eight pollen records reflecting climatic and environmental change from the tropical An... more We compare eight pollen records reflecting climatic and environmental change from the tropical Andes. Our analysis focuses on the last 50 ka, with particular emphasis on the Pleistocene to Holocene transition. We explore ecological grouping and downcore ordination results as two approaches for extracting environmental variability from pollen records. We also use the records of aquatic and shoreline vegetation as markers for lake level fluctuations, and precipitation change. Our analysis focuses on the signature of millennial-scale variability in the tropical Andes, in particular, Heinrich stadials and Greenland interstadials. We identify rapid responses of the tropical vegetation to this climate variability, and relate differences between sites to moisture sources and site sensitivity.
ABSTRACT The stability of the Earth's climate is strongly linked to the amount and spatia... more ABSTRACT The stability of the Earth's climate is strongly linked to the amount and spatial distribution of energy by atmospheric/oceanic processes from low to high latitudes. Past periods of relatively stable climate have been interrupted by sharp events, once a critical point has been passed and positive triggers and feedbacks propel change toward a contrasting mode. Additional mechanisms amplify or sustain climate changes that are already under way. High-resolution proxy archives are useful tools for characterizing these events and modes in the past, both in time and space, in order to assess the likelihood of sudden shifts, in particular within warm climate behaviour. In this respect, the PIG2LIG-4FUTURE database (Geophysical Research Abstracts Vol. 14, EGU2012-13825) contains alkenone-derived sea surface temperatures (117 marine sediment profiles) and stable oxygen isotope ratios (measured in ice cores and speleothems; 29 and 88 records respectively) with sufficient temporal resolution to understand global abrupt climate processes throughout the present interglacial (PIG) and the last interglacial (LIG), together with their deglaciations (d1 and d2). Records have been selected according to their inclusion of both the PIG and LIG intervals for the same location (no more than 45% of the sites), tight chronological control and calibration revised criteria. Data have been compiled into 200-year bins for regional stacks to help in identifying trends, transitions, boundary conditions, latitudinal temperature gradients, polar amplification and reorganisation of monsoon systems. The LIG relative to PIG anomalies are larger at mid latitudes (up to 6°C around 40N and 40S) than those for the tropics (less than 2°C from 20N to 20S). The amplitude of variation during the PIG is found to be no more than 2°C (few exceptions up to 4°C at northern sub-polar specific locations). Latitudinal distribution of anomalies appears connected to temperature seasonal contrast. The same response is not seen everywhere, particularly evident when climate is changing to a different state (e.g. deglaciation or glacial inception). Results show an apparent homogenous LIG-scenario of global cooling after full interglacial conditions, while the equivalent interval within the PIG is heterogeneous, e.g. a cooling trend is persistent in the northern Atlantic latitudes whereas a warming progression is evident at a number of tropical locations. These spatial differences give clues about mechanisms, location of forcings and sustainers. LIG snapshots at approximately 129 ka, 125 ka, 121 ka and 115 ka BP are compared with PIG results at 12 ka, 8 ka, 5 ka, and 3 ka BP, respectively. These snapshots illustrate how climate occasionally flip to contrasting states. Unlike gradual trends, they seem to be largely unpredictable in detail (intensity and rate of change) and could pose a significant challenge to quantifying the impact of climate changes. This sort of rapid variability may well be the response to an internal non-linear rhythmic throbbing of the climatic system, persistently repeated and manifested depending on regional particularities and specific global environmental conditions prior to the beginning of any transition.
Quality-control dashboards for North American records
Quality-control dashboards, Africa
Quality-control dashboards, for records from Antarctica
in GitHub Markdown format
This study analyzes coccolithophore abundance fluctuations (e.g., Emiliania huxleyi, Gephyrocapsa... more This study analyzes coccolithophore abundance fluctuations (e.g., Emiliania huxleyi, Gephyrocapsa specimens, and Florisphaera profunda) in core MD01-2444 sediment strata retrieved at the Iberian Margin, northeastern Atlantic Ocean. Coccolithophores are calcareous nannofossils, a major component of the oceanic phytoplankton, which provide information about past ecological and climatological variability. Results are supported by data on fossil organic compounds (sea surface temperatures, alkenones, and n-hexacosan-1-ol index) and geochemical analyses (benthic d13Ccc and planktonic d18Occ isotopes). Three scenarios are taken into account for this location at centennial-scale resolution over the last 70,000 years: the Holocene and the stadial and interstadial modes. The different alternatives are described by means of elements such as nutrients; upwelling phenomena; temperatures at surface and subsurface level; or the arrival of surface turbid, fresh, and cold waters due to icebergs, low sea level, increased aridity, and dust. During the Holocene, moderate primary productivity was observed (mainly concentrated in E. huxleyi specimens); surface temperatures were at maxima while the water column was highly ventilated by northern-sourced polar deep waters and warmer subsurface, nutrient-poor subtropical waters. Over most of the last glacial stadials, surface productivity weakened (higher F. profunda and reworked specimen percentages and lower diunsaturated and triunsaturated C37 alkenones); the arrival of cold Arctic surface waters traced by tetraunsaturated C37 peaks and large E. huxleyi, together with powerful ventilated southern-sourced polar deep waters, disturbed, in all likelihood, the delicate vertical equilibrium while preventing significant upwelling mixing. Finally, during the last glacial interstadials (lower F. profunda percentages, nonreworked material, and higher diunsaturated and triunsaturated C37 alkenones) a combined signal is observed: warm surface temperatures were concurrent with generally low oxyge [...]
Research is organised as a linked network of well-defined projects and targeted manuscripts, iden... more Research is organised as a linked network of well-defined projects and targeted manuscripts, identified and led by 2k members. This bottom-up concept of projects initiated and conducted by community members will further stimulate collaboration during Phase 3 of the 2k Network. PAGES 2k projects focus on specific scientific questions aligned with Phase 3 Themes, rather than being defined along regional boundaries. An enduring element from earlier phases is a culture of collegiality, transparency, and reciprocity. Phase 3 seeks to stimulate community-based projects and facilitate collaborations between researchers from different regions and career stages, drawing on the breadth, depth, broad expertise and input of the global PAGES 2k community. All PAGES 2k projects also promote best practises in Data Stewardship for the research community. Phase 3 seek to further develop collaborations with other research communities and engage with stakeholders at the project and network level through interaction with related institutions and initiatives such as Future Earth, WCRP, IPCC and EarthCube.
During the PROMESS campaign (summer 2004) a borehole (PRGL1) was drilled in the upper slope of th... more During the PROMESS campaign (summer 2004) a borehole (PRGL1) was drilled in the upper slope of the Gulf of Lions. Previous studies showed that the deposition of the sedimentary units at borehole PRGL1 was determined by changes in the discharge of the Rhone river, induced by sea level and climate variability with a strong 100 ka imprint. However, there are no detailed studies that focus on the glacial/interglacial transitions (i.e. Terminations) that define 100 ka Quaternary ice-age cycles. Here we present a high-resolution record of terrestrial long chain n-alkanes (C21 to C33) from MIS 3 to MIS 11 in order to monitor changes in the sediments deposited on the upper slope of the Gulf of Lions with the aim to provide new insight into the climatic events occurring during Terminations in the western Mediterranean Sea.Principal component analysis grouped n-alkane on the basis of the degree of maturation of organic matter (fresh/degraded) that allowed to monitor past variability in the source of the sediment deposited in the upper slope as a consequence of sea level and climate change. This information was used to estimate the impact that northern ice-sheet variability had on the western Mediterranean basin. As sea level started to fall, fresh terrestrial organic matter increased owing to the seaward migration of Rhone's mouth. Simultaneously, the decrease in sea level exposed old and reworked organic material from the Rhone's catchment, including the delta plain and the continental shelf, that was eroded and transported into our study site. This resulted in an increase in the proportion of degraded terrestrial organic matter together with sea level decrease. Aside from sea level changes, the proportion of fresh vs degraded organic matter seems to be affected by the amount of continental runoff, with an increasing proportion of fresh terrestrial organic matter occurring at times of reduced continental runoff. During the last glacial, the increase of fresh terrestrial organic matter was contemporaneous with Heinrich eve [...]
<p>The past two thousand years is a key interval for climate science. This period encompass... more <p>The past two thousand years is a key interval for climate science. This period encompasses both the era of human-induced global warming and a much longer interval when changes in Earth’s climate were governed principally by natural drivers and unforced variability. Since 2009, the Past Global Changes (PAGES) 2k Network has brought together hundreds of scientists from around the world to reconstruct and understand the climate of the Common Era using open and collaborative approaches to palaeoclimate science, including virtual meetings. The third phase of the network will end in December 2021. Here we highlight some key outputs of PAGES 2k and present the major themes and scientific questions emerging from recent surveys of the community. We explore how these might boost a new phase of PAGES 2k or a successor project(s). This year we will further reach out to the community through Town Hall consultations, vEGU and other meetings, and a PAGES 2k global webinar series. The aim of these activities is to foster development of post-2021 community-led PAGES initiatives that connect past and present climate.</p>
We compare eight pollen records reflecting climatic and environmental change from the tropical An... more We compare eight pollen records reflecting climatic and environmental change from the tropical Andes. Our analysis focuses on the last 50 ka, with particular emphasis on the Pleistocene to Holocene transition. We explore ecological grouping and downcore ordination results as two approaches for extracting environmental variability from pollen records. We also use the records of aquatic and shoreline vegetation as markers for lake level fluctuations, and precipitation change. Our analysis focuses on the signature of millennial-scale variability in the tropical Andes, in particular, Heinrich stadials and Greenland interstadials. We identify rapid responses of the tropical vegetation to this climate variability, and relate differences between sites to moisture sources and site sensitivity.
ABSTRACT The stability of the Earth's climate is strongly linked to the amount and spatia... more ABSTRACT The stability of the Earth's climate is strongly linked to the amount and spatial distribution of energy by atmospheric/oceanic processes from low to high latitudes. Past periods of relatively stable climate have been interrupted by sharp events, once a critical point has been passed and positive triggers and feedbacks propel change toward a contrasting mode. Additional mechanisms amplify or sustain climate changes that are already under way. High-resolution proxy archives are useful tools for characterizing these events and modes in the past, both in time and space, in order to assess the likelihood of sudden shifts, in particular within warm climate behaviour. In this respect, the PIG2LIG-4FUTURE database (Geophysical Research Abstracts Vol. 14, EGU2012-13825) contains alkenone-derived sea surface temperatures (117 marine sediment profiles) and stable oxygen isotope ratios (measured in ice cores and speleothems; 29 and 88 records respectively) with sufficient temporal resolution to understand global abrupt climate processes throughout the present interglacial (PIG) and the last interglacial (LIG), together with their deglaciations (d1 and d2). Records have been selected according to their inclusion of both the PIG and LIG intervals for the same location (no more than 45% of the sites), tight chronological control and calibration revised criteria. Data have been compiled into 200-year bins for regional stacks to help in identifying trends, transitions, boundary conditions, latitudinal temperature gradients, polar amplification and reorganisation of monsoon systems. The LIG relative to PIG anomalies are larger at mid latitudes (up to 6°C around 40N and 40S) than those for the tropics (less than 2°C from 20N to 20S). The amplitude of variation during the PIG is found to be no more than 2°C (few exceptions up to 4°C at northern sub-polar specific locations). Latitudinal distribution of anomalies appears connected to temperature seasonal contrast. The same response is not seen everywhere, particularly evident when climate is changing to a different state (e.g. deglaciation or glacial inception). Results show an apparent homogenous LIG-scenario of global cooling after full interglacial conditions, while the equivalent interval within the PIG is heterogeneous, e.g. a cooling trend is persistent in the northern Atlantic latitudes whereas a warming progression is evident at a number of tropical locations. These spatial differences give clues about mechanisms, location of forcings and sustainers. LIG snapshots at approximately 129 ka, 125 ka, 121 ka and 115 ka BP are compared with PIG results at 12 ka, 8 ka, 5 ka, and 3 ka BP, respectively. These snapshots illustrate how climate occasionally flip to contrasting states. Unlike gradual trends, they seem to be largely unpredictable in detail (intensity and rate of change) and could pose a significant challenge to quantifying the impact of climate changes. This sort of rapid variability may well be the response to an internal non-linear rhythmic throbbing of the climatic system, persistently repeated and manifested depending on regional particularities and specific global environmental conditions prior to the beginning of any transition.