Low-latitude mesopelagic nutrient recycling controls productivity and export.

Low-latitude (LL) oceans account for up to half of global net primary production and export1-5. It has been argued that the Southern Ocean dominates LL primary production and export6, with implications for the response of global primary production and export to climate change7. Here we applied observational analyses and sensitivity studies to an individual model to show, instead, that 72% of LL primary production and 55% of export is controlled by local mesopelagic macronutrient cycling. A total of 34% of the LL export is sustained by preformed macronutrients supplied from the Southern Ocean via a deeper overturning cell, with a shallow preformed northward supply, crossing 30° S through subpolar and thermocline water masses, sustaining only 7% of the LL export. Analyses of five Coupled Model Intercomparison Project Phase 6 (CMIP6) models, run under both high-emissions low-mitigation (shared socioeconomic pathway (SSP5-8.5)) and low-emissions high-mitigation (SSP1-2.6) climate scenarios for 1850-2300, revealed significant across-model disparities in their projections of not only the amplitude, but also the sign, of LL primary production. Under the stronger SSP5-8.5 forcing, with more substantial upper-ocean warming, the CMIP6 models that account for temperature-dependent remineralization promoted enhanced LL mesopelagic nutrient retention under warming, with this providing a first-order contribution to stabilizing or increasing, rather than decreasing, LL production under high emissions and low mitigation. This underscores the importance of a mechanistic understanding of mesopelagic remineralization and its sensitivity to ocean warming for predicting future ecosystem changes.

Global impacts of recent Southern Ocean cooling.

Since the beginning of the satellite era, Southern Ocean sea surface temperatures (SSTs) have cooled, despite global warming. While observed Southern Ocean cooling has previously been reported to have minimal impact on the tropical Pacific, the efficiency of this teleconnection has recently shown to be mediated by subtropical cloud feedbacks that are highly model-dependent. Here, we conduct a coupled model intercomparison of paired ensemble simulations under historical radiative forcing: one with freely evolving SSTs and the other with Southern Ocean SST anomalies constrained to follow observations. We reveal a global impact of observed Southern Ocean cooling in the model with stronger (and more realistic) cloud feedbacks, including Antarctic sea-ice expansion, southeastern tropical Pacific cooling, northward-shifted Hadley circulation, Aleutian low weakening, and North Pacific warming. Our results therefore suggest that observed Southern Ocean SST decrease might have contributed to cooler conditions in the eastern tropical Pacific in recent decades.

Pervasive alterations to snow-dominated ecosystem functions under climate change.

Climate change projections consistently demonstrate that warming temperatures and dwindling seasonal snowpack will elicit cascading effects on ecosystem function and water resource availability. Despite this consensus, little is known about potential changes in the variability of ecohydrological conditions, which is also required to inform climate change adaptation and mitigation strategies. Considering potential changes in ecohydrological variability is critical to evaluating the emergence of trends, assessing the likelihood of extreme events such as floods and droughts, and identifying when tipping points may be reached that fundamentally alter ecohydrological function. Using a single-model Large Ensemble with sophisticated terrestrial ecosystem representation, we characterize projected changes in the mean state and variability of ecohydrological processes in historically snow-dominated regions of the Northern Hemisphere. Widespread snowpack reductions, earlier snowmelt timing, longer growing seasons, drier soils, and increased fire risk are projected for this century under a high-emissions scenario. In addition to these changes in the mean state, increased variability in winter snowmelt will increase growing-season water deficits and increase the stochasticity of runoff. Thus, with warming, declining snowpack loses its dependable buffering capacity so that runoff quantity and timing more closely reflect the episodic characteristics of precipitation. This results in a declining predictability of annual runoff from maximum snow water equivalent, which has critical implications for ecosystem stress and water resource management. Our results suggest that there is a strong likelihood of pervasive alterations to ecohydrological function that may be expected with climate change.

Change in future climate due to Antarctic meltwater.

Meltwater from the Antarctic Ice Sheet is projected to cause up to one metre of sea-level rise by 2100 under the highest greenhouse gas concentration trajectory (RCP8.5) considered by the Intergovernmental Panel on Climate Change (IPCC). However, the effects of meltwater from the ice sheets and ice shelves of Antarctica are not included in the widely used CMIP5 climate models, which introduces bias into IPCC climate projections. Here we assess a large ensemble simulation of the CMIP5 model 'GFDL ESM2M' that accounts for RCP8.5-projected Antarctic Ice Sheet meltwater. We find that, relative to the standard RCP8.5 scenario, accounting for meltwater delays the exceedance of the maximum global-mean atmospheric warming targets of 1.5 and 2 degrees Celsius by more than a decade, enhances drying of the Southern Hemisphere and reduces drying of the Northern Hemisphere, increases the formation of Antarctic sea ice (consistent with recent observations of increasing Antarctic sea-ice area) and warms the subsurface ocean around the Antarctic coast. Moreover, the meltwater-induced subsurface ocean warming could lead to further ice-sheet and ice-shelf melting through a positive feedback mechanism, highlighting the importance of including meltwater effects in simulations of future climate.

Time of Emergence and Large Ensemble Intercomparison for Ocean Biogeochemical Trends.

Anthropogenically forced changes in ocean biogeochemistry are underway and critical for the ocean carbon sink and marine habitat. Detecting such changes in ocean biogeochemistry will require quantification of the magnitude of the change (anthropogenic signal) and the natural variability inherent to the climate system (noise). Here we use Large Ensemble (LE) experiments from four Earth system models (ESMs) with multiple emissions scenarios to estimate Time of Emergence (ToE) and partition projection uncertainty for anthropogenic signals in five biogeochemically important upper-ocean variables. We find ToEs are robust across ESMs for sea surface temperature and the invasion of anthropogenic carbon; emergence time scales are 20-30 yr. For the biological carbon pump, and sea surface chlorophyll and salinity, emergence time scales are longer (50+ yr), less robust across the ESMs, and more sensitive to the forcing scenario considered. We find internal variability uncertainty, and model differences in the internal variability uncertainty, can be consequential sources of uncertainty for projecting regional changes in ocean biogeochemistry over the coming decades. In combining structural, scenario, and internal variability uncertainty, this study represents the most comprehensive characterization of biogeochemical emergence time scales and uncertainty to date. Our findings delineate critical spatial and duration requirements for marine observing systems to robustly detect anthropogenic change.

Abrupt increase in Arctic-Subarctic wildfires caused by future permafrost thaw.

Unabated 21st-century climate change will accelerate Arctic-Subarctic permafrost thaw which can intensify microbial degradation of carbon-rich soils, methane emissions, and global warming. The impact of permafrost thaw on future Arctic-Subarctic wildfires and the associated release of greenhouse gases and aerosols is less well understood. Here we present a comprehensive analysis of the effect of future permafrost thaw on land surface processes in the Arctic-Subarctic region using the CESM2 large ensemble forced by the SSP3-7.0 greenhouse gas emission scenario. Analyzing 50 greenhouse warming simulations, which capture the coupling between permafrost, hydrology, and atmosphere, we find that projected rapid permafrost thaw leads to massive soil drying, surface warming, and reduction of relative humidity over the Arctic-Subarctic region. These combined processes lead to nonlinear late-21st-century regime shifts in the coupled soil-hydrology system and rapid intensification of wildfires in western Siberia and Canada.

Future Indian Ocean warming patterns.

Most future projections conducted with coupled general circulation models simulate a non-uniform Indian Ocean warming, with warming hotspots occurring in the Arabian Sea (AS) and the southeastern Indian Ocean (SEIO). But little is known about the underlying physical drivers. Here, we are using a suite of large ensemble simulations of the Community Earth System Model 2 to elucidate the causes of non-uniform Indian Ocean warming. Strong negative air-sea interactions in the Eastern Indian Ocean are responsible for a future weakening of the zonal sea surface temperature gradient, resulting in a slowdown of the Indian Ocean Walker circulation and the generation of southeasterly wind anomalies over the AS. These contribute to anomalous northward ocean heat transport, reduced evaporative cooling, a weakening in upper ocean vertical mixing and an enhanced AS future warming. In contrast, the projected warming in the SEIO is related to a reduction of low-cloud cover and an associated increase in shortwave radiation. Therefore, the regional character of air-sea interactions plays a key role in promoting future large-scale tropical atmospheric circulation anomalies with implications for society and ecosystems far outside the Indian Ocean realm.

Emerging unprecedented lake ice loss in climate change projections.

Seasonal ice in lakes plays an important role for local communities and lake ecosystems. Here we use Large Ensemble simulations conducted with the Community Earth System Model version 2, which includes a lake simulator, to quantify the response of lake ice to greenhouse warming and to determine emergence patterns of anthropogenic lake ice loss. Our model simulations show that the average duration of ice coverage and maximum ice thickness are projected to decrease over the next 80 years by 38 days and 0.23 m, respectively. In the Canadian Arctic, lake ice loss is accelerated by the cold-season polar amplification. Lake ice on the Tibetan Plateau decreases rapidly due to a combination of strong insolation forcing and ice-albedo feedbacks. Comparing the anthropogenic signal with natural variability represented by the Large Ensemble, we find that lake ecosystems in these regions may be exposed to no-analogue ice coverage within the next 4-5 decades.

Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms.

Today's surface ocean is saturated with respect to calcium carbonate, but increasing atmospheric carbon dioxide concentrations are reducing ocean pH and carbonate ion concentrations, and thus the level of calcium carbonate saturation. Experimental evidence suggests that if these trends continue, key marine organisms--such as corals and some plankton--will have difficulty maintaining their external calcium carbonate skeletons. Here we use 13 models of the ocean-carbon cycle to assess calcium carbonate saturation under the IS92a 'business-as-usual' scenario for future emissions of anthropogenic carbon dioxide. In our projections, Southern Ocean surface waters will begin to become undersaturated with respect to aragonite, a metastable form of calcium carbonate, by the year 2050. By 2100, this undersaturation could extend throughout the entire Southern Ocean and into the subarctic Pacific Ocean. When live pteropods were exposed to our predicted level of undersaturation during a two-day shipboard experiment, their aragonite shells showed notable dissolution. Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously.

Validation of claims-based diagnostic and procedure codes for cardiovascular and gastrointestinal serious adverse events in a commercially-insured population.

PURPOSE: To validate administrative claims codes with medical chart review for myocardial infarction (MI), ischemic stroke, and severe upper gastrointestinal (UGI) bleed events in a large, commercially-insured US population. METHODS: These validation studies were part of a larger study examining the risk of MI, ischemic stroke, and severe UGI bleeds in patients receiving a new prescription of selective cyclooxygenase (COX)-2 inhibitors (coxibs) and non-over-the-counter (OTC) non-steroidal anti-inflammatory drugs (NSAIDs), between 1 July 2002 and 30 September 2004. Patients from the study cohort and other health plan members from the HealthCore Integrated Research Database(SM) (HIRD) experiencing these events were selected for these studies. The positive predictive value (PPV) of each of the claims code algorithms, using medical chart review as the gold standard, was calculated. RESULTS: Two hundred charts per event were abstracted. The PPV for MI was 88.4% (177/200; 95%CI, 83.2-92.5%); PPV for ischemic stroke was 87.4% (175/200; 95%CI, 82.0-91.7%); PPV for severe UGI bleed was 56.5% (109/193; 95%CI, 49.2-63.6%). Refining the ischemic stroke claims algorithm resulted in a PPV of 95.5% (95%CI, 91.0-98.2%); refining the claims algorithm for severe UGI bleed resulted in a PPV of 87.8% (95%CI, 78.7-94.0%). CONCLUSION: The results suggest that, for certain adverse events, claims data can serve as the basis for pharmacoepidemiology research and drug safety surveillance in the US.

Emergence of Anthropogenic Signals in the Ocean Carbon Cycle.

Attribution of anthropogenically-forced trends in the climate system requires understanding when and how such signals will emerge from natural variability. We apply time-of-emergence diagnostics to a Large Ensemble of an Earth System Model, providing both a conceptual framework for interpreting the detectability of anthropogenic impacts in the ocean carbon cycle and observational sampling strategies required to achieve detection. We find emergence timescales ranging from under a decade to over a century, a consequence of the time-lag between chemical and radiative impacts of rising atmospheric CO2 on the ocean. Processes sensitive to carbonate-chemical changes emerge rapidly, such as impacts of acidification on the calcium-carbonate pump (10 years for the globally-integrated signal, 9-18 years regionally-integrated), and the invasion flux of anthropogenic CO2 into the ocean (14 globally, 13-26 regionally). Processes sensitive to the ocean's physical state, such as the soft-tissue pump, which depends on nutrients supplied through circulation, emerge decades later (23 globally, 27-85 regionally).

The formation of the ocean's anthropogenic carbon reservoir.

The shallow overturning circulation of the oceans transports heat from the tropics to the mid-latitudes. This overturning also influences the uptake and storage of anthropogenic carbon (Cant). We demonstrate this by quantifying the relative importance of ocean thermodynamics, circulation and biogeochemistry in a global biochemistry and circulation model. Almost 2/3 of the Cant ocean uptake enters via gas exchange in waters that are lighter than the base of the ventilated thermocline. However, almost 2/3 of the excess Cant is stored below the thermocline. Our analysis shows that subtropical waters are a dominant component in the formation of subpolar waters and that these water masses essentially form a common Cant reservoir. This new method developed and presented here is intrinsically Lagrangian, as it by construction only considers the velocity or transport of waters across isopycnals. More generally, our approach provides an integral framework for linking ocean thermodynamics with biogeochemistry.

Delay in diagnosis of alpha1-antitrypsin deficiency: a continuing problem.

BACKGROUND AND STUDY OBJECTIVES: Alpha1-antitrypsin (AAT) deficiency is common but under-recognized. A 1994 mail survey showed a long delay between the onset of symptoms and the initial diagnosis of AAT deficiency. In 2003, we carried out a similar mail survey of AAT-deficient individuals to determine whether any delay in diagnosis experienced by individuals with a more recent diagnosis had become shorter. We also determined whether individuals living near medical centers with an expressed interest in AAT deficiency experienced shorter diagnostic delays than those living at a distance. METHODS: Results from mail surveys of two different cohorts were compared: a 1994 survey of 304 individuals with severe AAT deficiency and a 2003 survey of 1,953 AAT-deficient individuals. In the 2003 survey cohort, diagnostic delay intervals were analyzed by calendar year of initial diagnosis, rural vs urban residence, visit to a liver or lung specialist within the last year, and living within 50 miles of a medical center with particular expertise in AAT deficiency. One thousand nine hundred fifty-three individuals responded to the 2003 mail survey (37.4%). RESULTS: In the 2003 cohort, the mean +/- SD diagnostic delay was 5.6 +/- 8.5 years, compared with 7.2 +/- 8.3 years for the 1994 cohort (p = 0.002). In the 2003 cohort, younger patients and male patients experienced shorter diagnostic delays than older patients and female patients (p < 0.0001 and p = 0.007, respectively). For example, the delay was 6.5 +/- 8.8 years for those born in the 1940s, as compared with 0.43 +/- 1.08 years for those born after 1980. Neither urban residence nor living near a center with expertise in AAT deficiency were associated with a shortened diagnostic delay interval. CONCLUSIONS: Although these results show some improvement in the mean diagnostic delay in the 9-year period separating the two studies, under-recognition of AAT deficiency persists. Diagnostic delay of AAT deficiency is longer in women and in older individuals. Educational efforts are underway to enhance clinicians' diagnostic suspicion of AAT deficiency and permit earlier diagnosis and attendant benefits.

An observing system simulation for Southern Ocean carbon dioxide uptake.

The Southern Ocean is critically important to the oceanic uptake of anthropogenic CO2. Up to half of the excess CO2 currently in the ocean entered through the Southern Ocean. That uptake helps to maintain the global carbon balance and buffers transient climate change from fossil fuel emissions. However, the future evolution of the uptake is uncertain, because our understanding of the dynamics that govern the Southern Ocean CO2 uptake is incomplete. Sparse observations and incomplete model formulations limit our ability to constrain the monthly and annual uptake, interannual variability and long-term trends. Float-based sampling of ocean biogeochemistry provides an opportunity for transforming our understanding of the Southern Ocean CO2 flux. In this work, we review current estimates of the CO2 uptake in the Southern Ocean and projections of its response to climate change. We then show, via an observational system simulation experiment, that float-based sampling provides a significant opportunity for measuring the mean fluxes and monitoring the mean uptake over decadal scales.

Impact of asthma control on sleep, attendance at work, normal activities, and disease burden.

BACKGROUND: The 2007 Expert Panel Report 3 asthma treatment guidelines place substantial emphasis on understanding the effectiveness of treatment strategies on outcomes such as disease control. OBJECTIVE: To assess the impact of asthma control on patient-reported outcomes and disease burden in a real-world setting. METHODS: Patients aged 18 to 64 years with moderate to severe asthma defined by medical and pharmaceutical use were asked to participate in a cross-sectional survey of asthma care, control, and burden. Patients were included if they had an International Classification of Diseases, Ninth Revision, Clinical Modification code for asthma, a prescription for an Expert Panel Report 3-defined controller medication (or combinations), and 24-month pre-index continuous eligibility. Patients with chronic obstructive pulmonary disease were excluded. Survey respondent data were linked to commercial health claims information to create the research database. The Asthma Therapy Assessment Questionnaire (ATAQ) was used as the measure of control. The ATAQ scores range from 0 to 4, with 0 indicating no asthma control problems. RESULTS: A total of 1,199 patients (73% women) completed the survey and had their claims data linked for analysis. Age, sex, and comorbidity index measures did not differ between respondents and nonrespondents. Only 12.2% of respondents scored 0 on the ATAQ, 77.0% scored 1 or 2, and 10.8% scored 3 or 4. The ATAQ scores were moderately correlated with patient-rated severity. Decreasing levels of asthma control were associated with greater prevalences of sleep problems, depression, functional impairment, and effect on work and regular activities. CONCLUSIONS: Approximately 88% of patients with moderate to severe asthma were not fully controlled despite anti-inflammatory drug treatment. Lack of asthma control is associated with substantial patient burden.

Impact of race and baseline PSA on longitudinal PSA.

There is an increasing debate regarding the frequency of prostate-specific antigen (PSA) testing and the current primary screening modality used to detect prostate cancer. The purpose of this study is to determine whether PSA screening intervals should be based on initial PSA. Our study explores longitudinal changes of PSA levels in black and white males separately. Study participants were 768 white and 450 black males attending an annual prostate cancer screening. We fit a longitudinal repeated measures model separately for blacks and whites and estimated the probability of PSA converting to greater than 4.0 ng/ml at a follow-up year given baseline PSA range among males without an abnormal DRE. Black and white males with a baseline PSA between 0 and 1.0 ng/ml, with a healthy or enlarged prostate, have a less than 1% chance that their PSA will increase above 4.0 ng/ml over the following 5 years. Black and white males with a PSA between 1.0 and 1.9 ng/ml have a less than 1% chance of PSA conversion to greater than 4.0 ng/ml over the next year. Our findings further support that annual screening for prostate cancer may not be necessary, specifically males with a baseline PSA less than 2.0 may not need to undergo annual screening. Our results suggest that race does not affect the longitudinal trend of PSA enough to warrant setting screening intervals based on race.