Periodic Reporting for period 1 - CLIMAGNET (How is the external climatic forcing affected by the Earth’s magnetic field?)
Período documentado: 2016-02-01 hasta 2018-01-31
Introduction. The following sentence contained in the publication (in 2013) of the Working Group I of the Intergovernmental Panel on Climate Change (IPCC) summarizes the problem addressed by the CLIMAGNET project: “the radionuclide records reflect not only solar activity, but also the geomagnetic field intensity and effects of their respective geochemical cycles and transport pathways. The corrections for these non-solar components, which are difficult to quantify, contribute to the overall error of the reconstructions”. In other words, the corrections in the rate of production of cosmogenic isotopes by the geomagnetic field (GF) intensity (among other non-solar effects) are not well established, and constitute the focal point of the CLIMAGNET proposal. The connection between GF and the production of isotopes can be briefly described as follows: if the intensity of the GF increases, the density of cosmic rays reaching the atmosphere decreases and, therefore, less rate of production of cosmogenic isotopes is expected. As indicated before, the rate of production is affected by the solar magnetic field, which serves as a basis for developing reconstructions of total solar irradiance provided that corrections for the influence of the GF can be developed. Therefore, a good knowledge of the GF variability is fundamental to appropriately isolate the corrections due to the GF from the solar influence, issue that is not being well considered in the current paleoclimatic reconstructions.
To reach this topic, the objectives of CLIMAGNET were divided into two main tasks:
Objective 1: Generation of a global paleomagnetic reconstructions for the last millennia using an appropriate weighting scheme of the paleomagnetic data.
Objective 2: After obtaining a database of radionuclides, they are used to establish a robust relation between geomagnetic field strength and variation rate of the cosmogenic isotopes. This correlation must be quantified in order to correct the solar forcing during the last millennia.
To reach this topic, the objectives of CLIMAGNET were divided into two main tasks:
Objective 1: Generation of a global paleomagnetic reconstructions for the last millennia using an appropriate weighting scheme of the paleomagnetic data.
Objective 2: After obtaining a database of radionuclides, they are used to establish a robust relation between geomagnetic field strength and variation rate of the cosmogenic isotopes. This correlation must be quantified in order to correct the solar forcing during the last millennia.
A) Scientific work and results.
The 2-year project CLIMAGNET has been developed according to the next steps grouped into the two main objectives.
1. A complete review of the paleomagnetic database has been done. To compile the input database we have used the global compilation GEOMAGI50v3.2 (http://geomagia.gfz-potsdam.de).
2. We have ranked the dataset into two different categories following different quality criteria based on their reliabilities.
3. An accurate GF global model has been developed using the archeomagnetic database detailed above. For modelling purposes, we have used the Spherical Harmonic Analysis technique in space and the penalized cubic B-splines in time. In order to assure the convergence of the model at the Core Mantle Boundary (CMB) a regularization matrix will be used using a new method of fitting to determine the most appropriate damping parameters by combining the minimum energy of the GF at the CMB surface and the power spectra of the obtained Gauss coefficients.
4. Compilation of radionuclide records. The time series of 14C and 10Be (along with other cosmogenic isotopes with potential for climate reconstructions) have been compiled. The 10Be is recorded in ice cores and the 14C in tree rings.
5. Review of the state of art. This part of the objective 2 corresponds to a new and interesting issue and its well understanding has been crucial for developing CLIMAGNET. First, it has been needed to study the possible problems involved in isotopes production and then, an analysis of the influence of the GF variations in the rate of variations of cosmogenic isotopes has been performed.
6. Develop mathematical approaches for climatic correlation for the last millennia. Results have shown that the geomagnetic field exerts a strong modulation of multi-centennial to millennial wavelengths (periods of 800 and 2200 years) that have so far been wrongly assigned to solar activity. In addition, our results, have demonstrated that the non-dipole terms of the GF produce maximum differences of 7% in the global average radiocarbon production rate.
B) Fellow’s training, Transfer of knowledge and career development.
The host institution has given the MSCA fellow the opportunity to acquire new experience necessaries to develop a productive research career at the University: teaching activities. The MSCA fellow has participated as assistant professor in different lessons of the official degree in Physics of the Complutense University (number of hours: 102). In addition, the MSCA fellow has been the tutor or supervisor 4 PhD students and 2 Master students. During the 2-yr of CLIMAGNET, 3 PhD students have presented their PhD dissertation. In addition, during the 2-year of project the MSCA fellow has carried out an important work of exploitation and dissemination with important publications in indexed journal and the participation in national and international meetings. One of the objectives of the framework programme H2020 is to approach the science challenges to the society “Science with and for Society” giving effective cooperation between science and society, building capacities and developing innovative ways of connecting science to society. In this sense an important effort has been carried out allowing CLIMAGNET reaches a broad public and not only a narrow scientific community. The MSCA fellow has organized and participated in different scientific social events (Science Week, European Research Night, etc.).
The 2-year project CLIMAGNET has been developed according to the next steps grouped into the two main objectives.
1. A complete review of the paleomagnetic database has been done. To compile the input database we have used the global compilation GEOMAGI50v3.2 (http://geomagia.gfz-potsdam.de).
2. We have ranked the dataset into two different categories following different quality criteria based on their reliabilities.
3. An accurate GF global model has been developed using the archeomagnetic database detailed above. For modelling purposes, we have used the Spherical Harmonic Analysis technique in space and the penalized cubic B-splines in time. In order to assure the convergence of the model at the Core Mantle Boundary (CMB) a regularization matrix will be used using a new method of fitting to determine the most appropriate damping parameters by combining the minimum energy of the GF at the CMB surface and the power spectra of the obtained Gauss coefficients.
4. Compilation of radionuclide records. The time series of 14C and 10Be (along with other cosmogenic isotopes with potential for climate reconstructions) have been compiled. The 10Be is recorded in ice cores and the 14C in tree rings.
5. Review of the state of art. This part of the objective 2 corresponds to a new and interesting issue and its well understanding has been crucial for developing CLIMAGNET. First, it has been needed to study the possible problems involved in isotopes production and then, an analysis of the influence of the GF variations in the rate of variations of cosmogenic isotopes has been performed.
6. Develop mathematical approaches for climatic correlation for the last millennia. Results have shown that the geomagnetic field exerts a strong modulation of multi-centennial to millennial wavelengths (periods of 800 and 2200 years) that have so far been wrongly assigned to solar activity. In addition, our results, have demonstrated that the non-dipole terms of the GF produce maximum differences of 7% in the global average radiocarbon production rate.
B) Fellow’s training, Transfer of knowledge and career development.
The host institution has given the MSCA fellow the opportunity to acquire new experience necessaries to develop a productive research career at the University: teaching activities. The MSCA fellow has participated as assistant professor in different lessons of the official degree in Physics of the Complutense University (number of hours: 102). In addition, the MSCA fellow has been the tutor or supervisor 4 PhD students and 2 Master students. During the 2-yr of CLIMAGNET, 3 PhD students have presented their PhD dissertation. In addition, during the 2-year of project the MSCA fellow has carried out an important work of exploitation and dissemination with important publications in indexed journal and the participation in national and international meetings. One of the objectives of the framework programme H2020 is to approach the science challenges to the society “Science with and for Society” giving effective cooperation between science and society, building capacities and developing innovative ways of connecting science to society. In this sense an important effort has been carried out allowing CLIMAGNET reaches a broad public and not only a narrow scientific community. The MSCA fellow has organized and participated in different scientific social events (Science Week, European Research Night, etc.).
CLIMAGNET has demonstrated that the geomagnetic field exerts a strong modulation of multi-centennial to millennial wavelengths (periods of 800 and 2200 years) that have so far been wrongly assigned to solar activity. This has important implications in our current knowledge of past solar activity, and consequently of the total solar irradiance (TSI). This should motivate the investigation of the possible geomagnetic field modulation at multi-centennial and centennial time-scales in order to better ascertain the past variability of solar activity. This requires the implementation of more precise spherical harmonic geomagnetic models and therefore, the availability of new paleomagnetic data for the Holocene. Moreover, this result challenges past and currently ongoing approaches to simulate past climate under the umbrella of the Paleoclimate Model Intercomparison Proyect, Phases 3 and 4 (PMIP). Within the PMIP frame, paleoclimate simulation experiments are planned using solar, volcanic and other natural and anthropogenic forcings as boundary conditions for transient climate experiments within the mid and late Holocene. On the basis of the results presented herein, the solar forcing reconstructions used in PMIP experiments are, with high confidence, prone to be contaminated with geomagnetic field variability, thus influencing with a spurious signal climate model simulations. Such contamination can have also consequences for climate model-proxy data comparison exercises and for our understanding of solar-climate relationships within the affected timescale intervals.