Mechanisms of decadal North Atlantic climate variability and implications for the recent cold anomaly

Decadal sea surface temperature (SST) fluctuations in the North Atlantic Ocean influence climate over adjacent land areas and are a major source of skill in climate predictions. However, the mechanisms underlying decadal SST variability remain to be fully understood. This study isolates the mechanisms driving North Atlantic SST variability on decadal time scales using low-frequency component analysis, which identifies the spatial and temporal structure of low-frequency variability. Based on observations, large ensemble historical simulations, and preindustrial control simulations, we identify a decadal mode of atmosphere–ocean variability in the North Atlantic with a dominant time scale of 13–18 years. Large-scale atmospheric circulation anomalies drive SST anomalies both through contemporaneous air–sea heat fluxes and through delayed ocean circulation changes, the latter involving both the meridional overturning circulation and the horizontal gyre circulation. The decadal SST anomalies alter the atmospheric meridional temperature gradient, leading to a reversal of the initial atmospheric circulation anomaly. The time scale of variability is consistent with westward propagation of baroclinic Rossby waves across the subtropical North Atlantic. The temporal development and spatial pattern of observed decadal SST variability are consistent with the recent observed cooling in the subpolar North Atlantic. This suggests that the recent cold anomaly in the subpolar North Atlantic is, in part, a result of decadal SST variability.publishedVersio

Disentangling global warming, multi-decadal variability, and El Niño in Pacific temperatures

A key challenge in climate science is to separate observed temperature changes into components due to internal variability and responses to external forcing. Extended integrations of forced and unforced climate models are often used for this purpose. Here we demonstrate a novel method to separate modes of internal variability from global warming based on differences in time scale and spatial pattern, without relying on climate models. We identify uncorrelated components of Pacific sea surface temperature variability due to global warming, the Pacific Decadal Oscillation (PDO), and the El Niño–Southern Oscillation (ENSO). Our results give statistical representations of PDO and ENSO that are consistent with their being separate processes, operating on different time scales, but are otherwise consistent with canonical definitions. We isolate the multidecadal variability of the PDO and find that it is confined to midlatitudes; tropical sea surface temperatures and their teleconnections mix in higher‐frequency variability. This implies that midlatitude PDO anomalies are more persistent than previously thought

Development of stable reporter system cloning luxCDABE genes into chromosome of Salmonella enterica serotypes using Tn7 transposon

<p>Abstract</p> <p>Background</p> <p>Salmonellosis may be a food safety problem when raw food products are mishandled and not fully cooked. In previous work, we developed bioluminescent <it>Salmonella enterica </it>serotypes using a plasmid-based reporting system that can be used for real-time monitoring of the pathogen's growth on food products in short term studies. In this study, we report the use of a Tn7-based transposon system for subcloning of <it>luxCDABE </it>genes into the chromosome of eleven <it>Salmonella enterica </it>serotypes isolated from the broiler production continuum.</p> <p>Results</p> <p>We found that the <it>lux </it>operon is constitutively expressed from the chromosome post-transposition and the <it>lux </it>cassette is stable without external pressure, i.e. antibiotic selection, for all <it>Salmonella enterica </it>serotypes used. Bioluminescence expression is based on an active electron transport chain and is directly related with metabolic activity. This relationship was quantified by measuring bioluminescence against a temperature gradient in aqueous solution using a luminometer. In addition, bioluminescent monitoring of two serotypes confirmed that our chicken skin model has the potential to be used to evaluate pathogen mitigation strategies.</p> <p>Conclusions</p> <p>This study demonstrated that our new stable reporting system eliminates bioluminescence variation due to plasmid instability and provides a reliable real-time experimental system to study application of preventive measures for <it>Salmonella </it>on food products in real-time for both short and long term studies.</p