Parfitt, R., Ummenhofer, C. C., Buckley, B. M., Hansen, K. G., & D'Arrigo, R. D. (2020). Distinct seasonal climate drivers revealed in a network of tree-ring records from Labrador, Canada. Clim Dyn , 54 (3-4), 1897–1911.
Abstract: Traditionally, high-latitude dendroclimatic studies have focused on measurements of total ring width (RW), with the maximum density of the latewood (MXD) serving as a complementary variable. Whilst MXD has typically improved the strength of the growing season climate connection over that of RW, its measurements are costly and time-consuming. Recently, a less costly and more time-efficient technique to extract density measurements has emerged, based on lignin's propensity to absorb blue light. This Blue Intensity (BI) methodology is based on image analyses of finely-sanded core samples, and the relative ease with which density measurements can be extracted allows for significant increases in spatio-temporal sample depth. While some studies have attempted to combine RW and MXD as predictors for summer temperature reconstructions, here we evaluate a systematic comparison of the climate signal for RW and latewood BI (LWBI) separately, using a recently updated and expanded tree ring database for Labrador, Canada. We demonstrate that while RW responds primarily to climatic drivers earlier in the growing season (January-April), LWBI is more responsive to climate conditions during late spring and summer (May-August). Furthermore, RW appears to be driven primarily by large-scale atmospheric dynamics associated with the Pacific North American pattern, whilst LWBI is more closely associated with local climate conditions, themselves linked to the behaviour of the Atlantic Multidecadal Oscillation. Lastly, we demonstrate that anomalously wide or narrow growth rings consistently respond to the same climate drivers as average growth years, whereas the sensitivity of LWBI to extreme climate conditions appears to be enhanced.
Kranz, S. A., Wang, S., Kelly, T. B., Stukel, M. R., Goericke, R., Landry, M. R., et al. (2020). Lagrangian Studies of Marine Production: A Multimethod Assessment of Productivity Relationships in the California Current Ecosystem Upwelling Region. J. Geophys. Res. Oceans , 125 (6).
Abstract: A multimethod process‐oriented investigation of diverse productivity measures in the California Current Ecosystem (CCE) Long‐Term Ecological Research study region, a complex physical environment, is presented. Seven multiday deployments covering a transition region from high to low productivity were conducted over two field expeditions (spring 2016 and summer 2017). Employing a Lagrangian study design, water parcels were followed over several days, comparing 24‐h in situ measurements (14C and 15NO3 ‐uptake, dilution estimates of phytoplankton growth, and microzooplankton grazing) with high‐resolution productivity measurements by fast repetition rate fluorometry (FRRF) and equilibrium inlet mass spectrometry (EIMS), and integrated carbon export measuremnts using sediment traps. Results show the importance of accounting for temporal and fine spatial scale variability when estimating ecosystem production. FRRF and EIMS measurements resolved diel patterns in gross primary and net community production. Diel productivity changes agreed well with comparably more traditional measurements. While differences in productivity metrics calculated over different time intervals were considerable, as those methods rely on different base assumptions, the data can be used to explain ecosystem processes which would otherwise have gone unnoticed. The processes resolved from this method comparison further understanding of temporal and spatial coupling and decoupling of surface productivity and potential carbon burial in a gradient from coastal to offshore ecosystems.
Roberts, M. J., Jackson, L. C., Roberts, C. D., Meccia, V., Docquier, D., Koenigk, T., et al. (2020). Sensitivity of the Atlantic Meridional Overturning Circulation to Model Resolution in CMIP6 HighResMIP Simulations and Implications for Future Changes. J. Adv. Model. Earth Syst. , , Accepted.
Abstract: A multi‐model, multi‐resolution ensemble using CMIP6 HighResMIP coupled experiments is used to assess the performance of key aspects of the North Atlantic circulation. The Atlantic Meridional Overturning Circulation (AMOC), and related heat transport, tends to become stronger as ocean model resolution is enhanced, better agreeing with observations at 26.5°N. However for most models the circulation remains too shallow compared to observations, and has a smaller temperature contrast between the northward and southward limbs of the AMOC. These biases cause the northward heat transport to be systematically too low for a given overturning strength. The higher resolution models also tend to have too much deep mixing in the subpolar gyre.
Wang, S., Kranz, S. A., Kelly, T. B., Song, H., Stukel, M. R., & Cassar, N. (2020). Lagrangian Studies of Net Community Production: The Effect of Diel and Multiday Nonsteady State Factors and Vertical Fluxes on O2 /Ar in a Dynamic Upwelling Region. J. Geophys. Res. Biogeosci. , 125 (6), e2019JG005569.
Abstract: The ratio of dissolved oxygen to argon in seawater is frequently employed to estimate rates of net community production (NCP) in the oceanic mixed layer. The in situ O2/Ar‐based method accounts for many physical factors that influence oxygen concentrations, permitting isolation of the biological oxygen signal produced by the balance of photosynthesis and respiration. However, this technique traditionally relies upon several assumptions when calculating the mixed‐layer O2/Ar budget, most notably the absence of vertical fluxes of O2/Ar and the principle that the air‐sea gas exchange of biological oxygen closely approximates net productivity rates. Employing a Lagrangian study design and leveraging data outputs from a regional physical oceanographic model, we conducted in situ measurements of O2/Ar in the California Current Ecosystem in spring 2016 and summer 2017 to evaluate these assumptions within a �worst‐case� field environment. Quantifying vertical fluxes, incorporating nonsteady state changes in O2/Ar, and comparing NCP estimates evaluated over several day versus longer timescales, we find differences in NCP metrics calculated over different time intervals to be considerable, also observing significant potential effects from vertical fluxes, particularly advection. Additionally, we observe strong diel variability in O2/Ar and NCP rates at multiple stations. Our results reemphasize the importance of accounting for vertical fluxes when interpreting O2/Ar‐derived NCP data and the potentially large effect of nonsteady state conditions on NCP evaluated over shorter timescales. In addition, diel cycles in surface O2/Ar can also bias interpretation of NCP data based on local productivity and the time of day when measurements were made.
Liu, Q., Tan, Z. - M., Sun, J., Hou, Y., Fu, C., & Wu, Z. (2020). Changing rapid weather variability increases influenza epidemic risk in a warming climate. Environmental Research Letters , 15 (4).
Abstract: The continuing change of the Earth's climate is believed to affect the influenza viral activity and transmission in the coming decades. However, a consensus of the severity of the risk of influenza epidemic in a warming climate has not been reached. It was previously reported that the warmer winter can reduce influenza epidemic-caused mortality, but this relation cannot explain the deadly influenza epidemic in many countries over northern mid-latitudes in the winter of 2017-2018, one of the warmest winters in recent decades. Here we reveal that the widely spread 2017-2018 influenza epidemic can be attributed to the abnormally strong rapid weather variability. We demonstrate, from historical data, that the large rapid weather variability in autumn can precondition the deadly influenza epidemic in the subsequent months in highly populated northern mid-latitudes; and the influenza epidemic season of 2017-2018 was a typical case. We further show that climate model projections reach a consensus that the rapid weather variability in autumn will continue to strengthen in some regions of northern mid-latitudes in a warming climate, implying that the risk of influenza epidemic may increase 20% to 50% in some highly populated regions in later 21st century.
Vinayachandran, P. N., Davidson, F., & Chassignet, E. P. (2020). Towards joint assessments, modern capabilities and new links for ocean prediction systems. Bull. Amer. Meteor. Soc. , 101 (4).
Abstract: Approximately 260 individuals from forecasting centers, research laboratories, academia, and industry representing 40 countries met to discuss recent developments in operational oceanography and brainstorm about the future directions of ocean prediction services.
Mende, M., & Misra, V. (2020). Time to Flatten the Curves on COVID-19 and Climate Change. Marketing Can Help. Journal of Public Policy & Marketing , .
Abstract: The health, economic, and social impact of the COVID-19 pandemic is unprecedented in our lifetime, and no individual in this globalized, interconnected world is immune from its effects. This pandemic is a fundamental challenge for consumers, companies, and governments. Against this background, our commentary underscores linkages between public health, environment, and economy and explores how lessons from COVID-19 can help prevent other large-scale disasters.1 We focus on global climate change (GCC), because rising temperatures increase the likelihood of future pandemics.2 Accordingly, experts consider GCC “the largest public health threat of the century” (Wyns 2020). Although societal crises are underresearched in marketing, we propose that marketers should add their expertise to help avoid future crises. Notably, the Journal of Public Policy & Marketing (JPP&M) is uniquely positioned as a premier outlet for corresponding research at the intersection of marketing and policy.
Misra, V., & Bhardwaj, A. (2020). The impact of varying seasonal lengths of the rainy seasons of India on its teleconnections with tropical sea surface temperatures. Atmos Sci Lett , 21 (3), 9658–9689.
Abstract: We present in this paper the interannual variability of seasonal temperature and rainfall in the Indian meteorological subdivisions (IMS) for boreal winter and summer seasons that take in to account the varying length of the seasons. Our study reveals that accounting for the variations in the length of the seasons produces stronger teleconnections between the seasonal anomalies of surface temperature and rainfall over India with corresponding sea surface temperature anomalies of the tropical Oceans (especially over the northern Indian and the equatorial Pacific Oceans) compared to the same teleconnections from fixed length seasons over the IMS. It should be noted that the IMS show significant spatial heterogeneity in these teleconnections.
Ajayi, A., Le Sommer, J., Chassignet, E., Molines, J. - M., Xu, X., Albert, A., et al. (2020). Spatial and Temporal Variability of the North Atlantic Eddy Field From Two Kilometric-Resolution Ocean Models. J. Geophys. Res. Oceans , 125 (5).
Abstract: Ocean circulation is dominated by turbulent geostrophic eddy fields with typical scales ranging from 10 to 300 km. At mesoscales (>50 km), the size of eddy structures varies regionally following the Rossby radius of deformation. The variability of the scale of smaller eddies is not well known due to the limitations in existing numerical simulations and satellite capability. Nevertheless, it is well established that oceanic flows (<50 km) generally exhibit strong seasonality. In this study, we present a basin‐scale analysis of coherent structures down to 10 km in the North Atlantic Ocean using two submesoscale‐permitting ocean models, a NEMO‐based North Atlantic simulation with a horizontal resolution of 1/60 (NATL60) and an HYCOM‐based Atlantic simulation with a horizontal resolution of 1/50 (HYCOM50). We investigate the spatial and temporal variability of the scale of eddy structures with a particular focus on eddies with scales of 10 to 100 km, and examine the impact of the seasonality of submesoscale energy on the seasonality and distribution of coherent structures in the North Atlantic. Our results show an overall good agreement between the two models in terms of surface wave number spectra and seasonal variability. The key findings of the paper are that (i) the mean size of ocean eddies show strong seasonality; (ii) this seasonality is associated with an increased population of submesoscale eddies (10�50 km) in winter; and (iii) the net release of available potential energy associated with mixed layer instability is responsible for the emergence of the increased population of submesoscale eddies in wintertime.
Kim, D., Lee, S. - K., Lopez, H., Foltz, G. R., Misra, V., & Kumar, A. (2020). On the Role of Pacific-Atlantic SST Contrast and Associated Caribbean Sea Convection in August-October U.S. Regional Rainfall Variability. Geophys. Res. Lett. , 47 (11).
Abstract: This study investigates the large‐scale atmospheric processes that lead to U.S. precipitation variability in late summer to midfall (August–October; ASO) and shows that the well‐recognized relationship between North Atlantic Subtropical High and U.S. precipitation in peak summer (June–August) significantly weakens in ASO. The working hypothesis derived from our analysis is that in ASO convective activity in the Caribbean Sea, modulated by the tropical Pacific‐Atlantic sea surface temperature (SST) anomaly contrast, directly influences the North American Low‐Level Jet and thus U.S. precipitation east of the Rockies, through a Gill‐type response. This hypothesis derived from observations is strongly supported by a long‐term climate model simulation and by a linear baroclinic atmospheric model with prescribed diabatic forcings in the Caribbean Sea. This study integrates key findings from previous studies and advances a consistent physical rationale that links the Pacific‐Atlantic SST anomaly contrast, Caribbean Sea convective activity, and U.S. rainfall in ASO.
