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The β-decay half lives of nuclei near the r-process path are critical information required for abundance calculations, especially those near neutron number N = 82. Specifically, the nuclei below doubly-magic 132Sn are key, and play an important role in the formation and shape of the second r-process abundance peak. The half lives in this region are challenging to measure due to the significant β-delayed neutron decay branches and the population of isomeric states with half lives comparable to the ground states. However, by measuring the time distribution of γ rays, these complications can be eliminated. This requires, however, a very effcient γ-ray spectrometer since the production of isotopes in this region is very limited. The new GRIFFIN array at TRIUMF-ISAC provides the high effciency required for these measurements. Recent improvements in the quality of the beams produced at TRIUMF, employing the IG-LIS device, are outlined, as well as the current status of the ARIEL facility. The GRIFFIN spectrometer and its use are briefly described. The experiment to measure the half lives of 128-130Cd is outlined and the results given, and some examples of the power of GRIFFIN to expand decay schemes, specifically for the decay of 128Cd to 128In, are given.

Abstract Understanding climate variability across interannual to centennial timescales is critical, as it encompasses the natural range of climate fluctuations that early human agricultural societies had to adapt to. Deviations from the long-term mean climate are often associated with both societal collapse and periods of prosperity and expansion. Here, we show that contrary to what global paleoproxy reconstructions suggest, the mid to late-Holocene was not a period of climate stability. We use mid- to late-Holocene Earth System Model simulations, forced by state-of-the-art reconstructions of external climate forcing to show that eleven long-lasting cold periods occurred in the Northern Hemisphere during the past 8000 years. These periods correlate with enhanced volcanic activity, where the clustering of volcanic eruptions induced a prolonged cooling effect through gradual ocean-sea ice feedback. These findings challenge the prevailing notion of the Holocene as a period characterized by climate stability, as portrayed in multi-proxy climate reconstructions. Instead, our simulations provide an improved representation of amplitude and timing of temperature variations on sub-centennial timescales.

The anthropogenically intensified greenhouse effect has caused a radiative imbalance at the top of the atmosphere during the industrial period. This, in turn, has led to an energy surplus in various components of the Earth system, with the ocean storing the largest part. The land contribution ranks second with the latest observational estimates based on borehole temperature profiles, which quantify the terrestrial energy surplus to be 6 % in the last 5 decades, whereas studies based on state-of-the-art climate models scale it down to 2 %. This underestimation stems from land surface models (LSMs) having a subsurface that is too shallow, which severely constrains the land heat uptake simulated by Earth system models (ESMs). A forced simulation of the last 2000 years with the Max Planck Institute ESM (MPI-ESM) using a deep LSM captures 4 times more heat than the standard shallow MPI-ESM simulations in the historical period, well above the estimates provided by other ESMs. However, deepening the LSM does not remarkably affect the simulated surface temperature. It is shown that the heat stored during the historical period by an ESM using a deep LSM component can be accurately estimated by considering the surface temperatures simulated by the ESM using a shallow LSM and propagating them with a standalone forward model. This result is used to derive estimates of land heat uptake using all available observational datasets, reanalysis products, and state-of-the-art ESM experiments. This approach yields values of 10.5–16.0 ZJ for 1971–2018, which are 12 %–42 % smaller than the latest borehole-based estimates (18.2 ZJ).

Abstract The non‐local model of mixing based on internal wave breaking, IDEMIX, is implemented as an enhancement of a turbulent kinetic energy closure model in three non‐eddy resolving general circulation ocean models that differ in the discretization and choice of computational grids. In IDEMIX internal wave energy is generated by an energy flux resulting from near‐inertial waves induced by wind forcing at the surface, and at the bottom, by an energy flux that parameterizes the transfer of energy between baroclinic and barotropic tides. In all model simulations with IDEMIX, the mixing work is increased compared to the reference solutions without IDEMIX, reaching values in better agreement with finestructure observations. Furthermore, the horizontal structure of the mixing work is more realistic as a consequence of the heterogeneous forcing functions. All models with IDEMIX simulate deeper thermocline depths related to stronger shallow overturning cells in the Indo‐Pacific. In the North Atlantic, deeper mixed layers in simulations with IDEMIX are associated with an increased Atlantic overturning circulation and an increase of northward heat transports toward more realistic values. The response of the deep Indo‐Pacific overturning circulation and the weak bottom cell of the Atlantic to the inclusion of IDEMIX is incoherent between the models, suggesting that additional unidentified processes and numerical mixing may confound the analysis. Applying different tidal forcing functions leads to simulation differences that are small compared to differences between the different models or between simulations with IDEMIX and without IDEMIX.

Abstract Current global warming results in an uptake of heat by the Earth system, which is distributed among the different components of the climate system. However, current‐generation climate models deliver heat inventory and partitioning estimates of Earth system components that differ from recent observations. Here we investigate the global heat distribution under warming by using fully‐coupled CMIP6 Earth system model experiments, including a version of the MPI‐ESM with a deep land model component, accommodating the required space for more realistic terrestrial heat storage. The results show that sufficiently deep land models exert increased subsurface land heat uptake, leading to a heat uptake partitioning among the Earth system components that is closer to observational estimates. The results are relevant for the understanding of Earth's heat partitioning and highlight the importance of the land heat sink in the Earth heat inventory.

The decay of excited states of the nucleus 135Sn, with three neutrons outside the doubly-magic 132Sn core, was studied in an experiment performed at the Radioactive Isotope Beam Factory at RIKEN. Several γ rays emitted from excited 135Sn ions were observed following one-neutron and one-neutron-one-proton removal from 136Sn and 137Sb beams, respectively, on a beryllium target at relativistic energies. Based on the analogy to 133Sn populated via one-neutron removal from 134Sn, an excitation energy of 695(15) keV is assigned to the 3/2− state with strongest single-particle character in 135Sn. This result provides the first direct information about the evolution of the neutron shell structure beyond N=82 and thus allows for a crucial test of shell-model calculations in this region. The experimental findings are in full agreement with calculations performed employing microscopic effective two-body interactions derived from CD-Bonn and N3LO nucleon-nucleon potentials, which do not predict a pronounced subshell gap at neutron number N=90. The occurrence of such a gap in 140Sn, i.e., when the 1f7/2 orbital is completely filled, had been proposed in the past, in analogy to the magicity of 48Ca, featuring a completely filled 0f7/2 orbital one harmonic oscillator shell below.

Abstract Classical novae are thermonuclear explosions in stellar binary systems, and important sources of 26Al and 22Na. While γ rays from the decay of the former radioisotope have been observed throughout the Galaxy, 22Na remains untraceable. Its half-life (2.6 yr) would allow the observation of its 1.275 MeV γ-ray line from a cosmic source. However, the prediction of such an observation requires good knowledge of its nucleosynthesis. The 22Na(p, γ)23Mg reaction remains the only source of large uncertainty about the amount of 22Na ejected. Its rate is dominated by a single resonance on the short-lived state at 7785.0(7) keV in 23Mg. Here, we propose a combined analysis of particle-particle correlations and velocity-difference profiles to measure femtosecond nuclear lifetimes. The application of this method to the study of the 23Mg states, places strong limits on the amount of 22Na produced in novae and constrains its detectability with future space-borne observatories.

The investigation of the excitation energies of the 21+ –states in the neutron-rich Cd isotopes shows an irregular behaviour when approaching the neutron shell-closure at N = 82. The energy of the 21+–state in 128Cd is lower than the one in 126Cd. The transition strength B(E2, 0gs+ → 21+) in the even isotopes 122−128Cd was measured in Coulomb excitation experiments with the high-purity germanium detector array MINIBALL at REXISOLDE (CERN). The values for 122,124Cd coincide with beyond-mean-field calculations with a resultant prolate deformation, whereas 126,128Cd are better described by shell-model calculations.

The first EURICA campaign with high intensity Uranium beams took place at RIKEN in November/December 2012. Within this campaign experiment NP1112-RIBF85 was performed dedicated to the study of the isomeric and beta decays of neutronrich Cd, In, Sn and Sb isotopes towards and beyond the N=82 neutron shell closure. In this contribution we present a first status report of the analysis of the extensive data set obtained in this experiment.

The g factor of the first excited 2+ state of 72Zn has been measured using the Low Velocity Transient Field (LVTF) technique in combination with Coulomb excitation in inverse kinematics. The aim of the experiment was to test the viability of this method when applied to short-lived radioactive ISOL beams, in particular in comparison to the alternative High Velocity Transient Field (HVTF) technique using fragment beams. The result obtained for g(2+) in 72Zn in the present experiment follows the trend observed for the lighter stables Zn isotopes.

Excited states in the Tz=0,−1 nuclei 62Ga and 62Ge were populated in direct reactions of relativistic radioactive ion beams at the RIBF. Coincident γ rays were measured with the DALI2+ array and uniquely assigned to the A=62 isobars. In addition, 62Ge was also studied independently at JYFL-ACCLAB using the 24Mg(40Ca,2n)62Ge fusion-evaporation reaction. The first excited T=1,Jπ=2+ states in 62Ga and 62Ge were identified at 979(1) and 965(1) keV, respectively, resolving discrepant interpretations in the literature. States beyond the first 2+ state in 62Ge were also identified for the first time in the present work. The results are compared with shell-model calculations in the fp model space. Mirror and triplet energy differences are analyzed in terms of individual charge-symmetry and charge-independence breaking contributions. The MED results confirm the shrinkage of the p-orbits' radii when they are occupied by at least one nucleon on average.

The Atlantic meridional overturning circulation (AMOC) is an important part of our climate system. The AMOC is predicted to weaken under climate change; however, theories suggest that it may have a tipping point beyond which recovery is difficult, hence showing quasi-irreversibility (hysteresis). Although hysteresis has been seen in simple models, it has been difficult to demonstrate in comprehensive global climate models. Here, we outline a set of experiments designed to explore AMOC hysteresis and sensitivity to additional freshwater input as part of the North Atlantic Hosing Model Intercomparison Project (NAHosMIP). These experiments include adding additional freshwater (hosing) for a fixed length of time to examine the rate and mechanisms of AMOC weakening and whether the AMOC subsequently recovers once hosing stops. Initial results are shown from eight climate models participating in the Sixth Coupled Model Intercomparison Project (CMIP6). The AMOC weakens in all models as a result of the freshening, but once the freshening ceases, the AMOC recovers in half of the models, and in the other half it stays in a weakened state. The difference in model behaviour cannot be explained by the ocean model resolution or type nor by details of subgrid-scale parameterisations. Likewise, it cannot be explained by previously proposed properties of the mean climate state such as the strength of the salinity advection feedback. Instead, the AMOC recovery is determined by the climate state reached when hosing stops, with those experiments where the AMOC is weakest not experiencing a recovery.

Abstract Small‐to‐moderate volcanic eruptions can lead to significant surface cooling when they occur clustered, as observed in recent decades. In this study, based on new high‐resolution ice‐core data from Greenland, we produce a new volcanic forcing data set that includes several small‐to‐moderate eruptions not included in prior reconstructions and investigate their climate impacts of the early 19th century through ensemble simulations with the Max Planck Institute Earth System Model. We find that clustered small‐to‐moderate eruptions produce significant additional global surface cooling (∼0.07 K) during the period 1812–1820, superposing with the cooling by large eruptions in 1809 (unidentified location) and 1815 (Tambora). This additional cooling helps explain the reconstructed long‐lasting cooling after the large eruptions, but simulated regional impacts cannot be confirmed with reconstructions due to a low signal‐to‐noise ratio. This study highlights the importance of small‐to‐moderate eruptions for climate simulations as their impacts can be comparable with that of solar irradiance changes.

In the Northern Hemisphere, the mid-6th century was one of the coldest periods of the last 2000 years, which was initiated by volcanic eruptions in 536 and 540 CE. Here, we study the effect of this volcanic double event on the climate and society in Scandinavia with a special focus on southern Norway. Using an ensemble of Max Planck Institute Earth system model transient simulations for 521–680 CE, temperature, precipitation, and atmospheric circulation patterns are analyzed. The simulated cooling magnitude is used as input for a growing degree day (GDD) model setup for three different study areas in southern Norway, representative of typical meteorological and landscape conditions. Pollen from bogs inside these study areas are analyzed at high resolution (1–3 cm sample intervals) to give insights into the validity of the GDD model setup with regard to the volcanic climate impact on the regional scale and to link the different data sets with the archeological records. We find that after the 536 and 540 CE double event, a maximum surface air cooling of up to 3.5 ∘C during the mean growing season is simulated regionally for southern Norway. With a scenario cooling of 3 ∘C, the GDD model indicates crop failures were likely in our northernmost and western study areas, while crops were more likely to mature in the southeastern study area. These results are in agreement with the pollen records from the respective areas. Archeological excavations show, however, a more complex pattern for the three areas with abandonment of farms and severe social impacts but also a continuation of occupation or a mix of those. Finally, we discuss the likely climatic and societal impacts of the 536 and 540 CE volcanic double event by synthesizing the new and available data sets for the whole Scandinavia.

State-of-the-art Earth system models typically employ grid spacings of O(100 km), which is too coarse to explicitly resolve main drivers of the flow of energy and matter across the Earth system. In this paper, we present the new ICON-Sapphire model configuration, which targets a representation of the components of the Earth system and their interactions with a grid spacing of 10 km and finer. Through the use of selected simulation examples, we demonstrate that ICON-Sapphire can (i) be run coupled globally on seasonal timescales with a grid spacing of 5 km, on monthly timescales with a grid spacing of 2.5 km, and on daily timescales with a grid spacing of 1.25 km; (ii) resolve large eddies in the atmosphere using hectometer grid spacings on limited-area domains in atmosphere-only simulations; (iii) resolve submesoscale ocean eddies by using a global uniform grid of 1.25 km or a telescoping grid with the finest grid spacing at 530 m, the latter coupled to a uniform atmosphere; and (iv) simulate biogeochemistry in an ocean-only simulation integrated for 4 years at 10 km. Comparison of basic features of the climate system to observations reveals no obvious pitfalls, even though some observed aspects remain difficult to capture. The throughput of the coupled 5 km global simulation is 126 simulated days per day employing 21 % of the latest machine of the German Climate Computing Center. Extrapolating from these results, multi-decadal global simulations including interactive carbon are now possible, and short global simulations resolving large eddies in the atmosphere and submesoscale eddies in the ocean are within reach.

The climate of the Northern Hemisphere (NH) in the mid-6th century was one of the coldest during the last 2 millennia based on multiple paleo-proxies. While the onset of this cold period can be clearly connected to the volcanic eruptions in 536 and 540 Common Era (CE), the duration, extent, and magnitude of the cold period are uncertain. Proxy data are sparse for the first millennium, which compounds the uncertainties of the reconstructions. To better understand the mechanisms of the prolonged cooling, we analyze new transient simulations over the Common Era and enhance the representation of mid-6th to 7th century climate by additional ensemble simulations covering 520–680 CE. We use the Max Planck Institute Earth System Model to apply the external forcing as recommended in the Paleoclimate Modelling Intercomparison Project phase 4. After the four large eruptions in 536, 540, 574, and 626 CE, a significant mean surface climate response in the NH lasting up to 20 years is simulated. The 2 m air temperature shows a cooling over the Arctic in winter, corresponding to the increase in Arctic sea ice, mainly in the Labrador Sea and to the east of Greenland. The increase in sea-ice extent relates to a decrease in the northward ocean heat transport into the Arctic within the first 2 years after the eruptions and to an increase in the Atlantic meridional overturning circulation, which peaks 10 years after the eruptions. A decrease in the global ocean heat content is simulated after the eruptions that does not recover during the simulation period. These ocean–sea-ice interactions sustain the surface cooling, as the cooling lasts longer than is expected solely from the direct effects of the volcanic forcing, and are thus responsible for the multi-decadal surface cooling. In boreal summer, the main cooling occurs over the continents at midlatitudes. A dipole pattern develops with high sea level pressure and a decrease in both precipitation and evaporation poleward of 40∘ N. In addition, more pronounced cooling over land compared to ocean leads to an enhanced land–sea contrast. While our model ensemble simulations show a similar ∼20-year summer cooling over NH land after the eruptions as tree ring reconstructions, a volcanic-induced century-long cooling, as reconstructed from tree ring data, does not occur in our simulations.

Abstract Northern Hemisphere (NH) climate has experienced various coherent wintertime multidecadal climate trends in stratosphere, troposphere, ocean, and cryosphere. However, the overall mechanistic framework linking these trends is not well established. Here we show, using long-term transient forced coupled climate simulation, that large parts of the coherent NH-multidecadal changes can be understood within a damped coupled stratosphere/troposphere/ocean-oscillation framework. Wave-induced downward propagating positive stratosphere/troposphere-coupled Northern Annular Mode (NAM) and associated stratospheric cooling initiate delayed thermohaline strengthening of Atlantic overturning circulation and extratropical Atlantic-gyres. These increase the poleward oceanic heat transport leading to Arctic sea-ice melting, Arctic warming amplification, and large-scale Atlantic warming, which in turn initiates wave-induced downward propagating negative NAM and stratospheric warming and therefore reverse the oscillation phase. This coupled variability improves the performance of statistical models, which project further weakening of North Atlantic Oscillation, North Atlantic cooling and hiatus in wintertime North Atlantic-Arctic sea-ice and global surface temperature just like the 1950s–1970s.

Abstract The Atlantic Meridional Overturning Circulation (AMOC) is a key feature of the North Atlantic with global ocean impacts. The AMOC's response to past changes in forcings during the Holocene provides important context for the coming centuries. Here, we investigate AMOC trends using an emerging set of transient simulations using multiple global climate models for the past 6,000 years. Although some models show changes, no consistent trend in overall AMOC strength during the mid‐to‐late Holocene emerges from the ensemble. We interpret this result to suggest no overall change in AMOC, which fits with our assessment of available proxy reconstructions. The decadal variability of the AMOC does not change in ensemble during the mid‐ and late‐Holocene. There are interesting AMOC changes seen in the early Holocene, but their nature depends a lot on which inputs are used to drive the experiment.

Abstract This work provides evidence of the influence of large volcanic eruptions on Sahel rainfall relying on PMIP4/past1000 multi‐model simulations, covering the last millennium. A classification of volcanic eruptions in the last millennium according to the meridional symmetry of the associated radiative forcing reveals different mechanisms of the West African Monsoon response at inter‐annual timescale. In all cases, these simulated changes result in Sahel drying up to 2 years after an eruption. Besides, we add evidence of a role of varying volcanic activity across the past millennium in the Sahel precipitation variability at multi‐decadal to secular timescales.