Northern hemisphere jet stream position indices as diagnostic tools for climate and ecosystem dynamics

The latitudinal position of the Northern Hemisphere jet stream (NHJ) modulates the occurrence and frequency of extreme weather events. Precipitation anomalies in particular are associated with NHJ variability; the resulting floods and droughts can have considerable societal and economic impacts. This study develops a new climatology of the 300-hPa NHJ using a bottom-up approach based on seasonally explicit latitudinal NHJ positions. Four seasons with coherent NHJ patterns were identified (January-February, April-May, July-August, and October-November), along with 32 longitudinal sectors where the seasonal NHJ shows strong spatial coherence. These 32 longitudinal sectors were then used as NHJ position indices to examine the influence of seasonal NHJ position on the geographical distribution of NH precipitation and temperature variability and their link to atmospheric circulation pattern. The analyses show that the NHJ indices are related to broad-scale patterns in temperature and precipitation variability, in terrestrial vegetation productivity and spring phenology, and can be used as diagnostic/prognostic tools to link ecosystem and socioeconomic dynamics to upper-level atmospheric patterns

Climatic and volcanic forcing of tropical belt northern boundary over the past 800 years

The position of the northern boundary of the tropical belt affects the hydroclimate of many arid and semi-arid regions in the Northern Hemisphere. Widening of the tropical belt since the 1970s has largely been attributed to anthropogenic forcing. However, the relative influence of natural drivers of tropical belt expansion and contraction before this time is poorly understood. Here we use data on tree-ring widths from five mid-latitude regions in the Northern Hemisphere to reconstruct the movement of the northern boundary of the early spring tropical belt over the past 800 years (AD 1203-2003). Our reconstruction explains 45% of the interannual variance in the latitudinal extent of the Hadley circulation, a metric of the position of the tropical belt boundary. We find that the tropical belt contracted (expanded) during positive (negative) phases of the El Nino Southern Oscillation and Pacific North American teleconnection patterns. The tropical belt also contracted significantly following major volcanic events that injected sulfur into the stratosphere. The longest period of persistent tropical belt expansion occurred in the late sixteenth century, during one of the coldest periods of the Little Ice Age. Our results warn of potential socioeconomic consequences of future variations in tropical belt width driven by natural climate variability or stratospheric aerosol injections, whether volcanic or artificial

La séquence climatique continentale des Echets (alt.: 267 m, Ain, France): état de l'art des études multiproxies menées à bien sur les profils EC1 et EC3 entre la fin du Riss et le Pléniglaciaire würmien.

Cette étude est réalisée dans le cadre d'un groupement de compétences ("Les Echets Working Group") et du Groupement de Laboratoires Géoprospective de l'Andra, avec un financement multinational. A ce jour les principaux résultats sont les suivants. 1- Pendant le tardiglaciaire rissien et le stade de Caluire (Zeifen-Kattegat, H 11 ), des végétations successivement forestières boréales puis steppiques se mettent en place. Les taux de carbone minéral (exogène, loess) restent élevés au début de l'Eémien, alors qu'une chênaie mixte se met en place. C'est aussi le cas pendant les stades et le début des interstades du OIS 5. 2 - Les données biologiques et le rapport S2/S3CO2>4 indiquent que le climat devient plus humide dès l'immixtion de Taxus au sein de la chênaie éémienne. Le retour de la sapinière à la fin de l'Eémien, traduit un ultime réchauffement du climat avant le refroidissement du Mélisey 1 (OIS 5d). 3 - Le St Germain 1 se distingue par sa très forte variabilité climatique: i) au début, événements froids EC1 14a et Montaigu; ii) à la fin, un événement froid (EC1 19a, homologue du C22) et événement tempéré (EC1 19b, homologue du DO 22). 4 - Pendant les stades froids du Mélisey 1 (OIS 5d) et 2 (OIS 5b), les Chironomides indiquent des Tjuil comprises entre 10 et 14°C et un abaissement bathymétrique lacustre. 5 - Au St Germain 2 (OIS 5a), les maximums concordants de Carpinus et de S2/S3CO2>4 indiquent une élévation de l'humidité. 6 - Pendant le Pléniglaciaire würmien, l'évolution concordante et itérative du pollen de la taïga, du COT et du S2/S3CO2>4 pourrait correspondre aux pics thermiques mis en évidence pendant le OIS 3. Le "modèle" chronologique de l'ensemble de la séquence des Echets sera établi à partir des techniques OSL, C14 et Ar/Ar (sur téphras). Les mesures paléomagnétiques montrent que EC1 recèle l'empreinte des "excursions" de Blake (115-120 ka), Laschamps (40 ka) et Mono (32 ka). Les reconstructions climatiques mutiproxies sont en cours, de même que l'édification d'un pont scientifique Continent-Océan-Glace car, plus que d'autres, les séquences continentales proxi-atlantiques françaises, vieilles de 400 ka dans le Massif Central, sont aptes à percevoir la variabilité climatique mise en évidence dans les archives globales et les autres compartiments du "système Terre"

A high-resolution Late Glacial to Holocene record of environmental change in the Mediterranean from Lake Ohrid (Macedonia/Albania)

Lake Ohrid (Macedonia/Albania) is the oldest extant lake in Europe and exhibits an outstanding degree of endemic biodiversity. Here, we provide new high-resolution stable isotope and geochemical data from a 10 m core (Co1262) through the Late Glacial to Holocene and discuss past climate and lake hydrology (TIC, δ13Ccalcite, δ18Ocalcite) as well as the terrestrial and aquatic vegetation response to climate (TOC, TOC/N, δ13Corganic, Rock Eval pyrolysis). The data identifies 3 main zones: (1) the Late Glacial–Holocene transition represented by low TIC and TOC contents, (2) the early to mid-Holocene characterised by high TOC and increasing TOC/N and (3) the Late Holocene–Present which shows a marked decrease in TIC and TOC. In general, an overall trend of increasing δ18Ocalcite from 9 ka to present suggests progressive aridification through the Holocene, consistent with previous records from Lake Ohrid and the wider Mediterranean region. Several proxies show commensurate excursions that imply the impact of short-term climate oscillations, such as the 8.2 ka event and the Little Ice Age. This is the best-dated and highest resolution archive of past Late Glacial and Holocene climate from Lake Ohrid and confirms the overriding influence of the North Atlantic in the north-eastern Mediterranean. The data presented set the context for the International Continental scientific Drilling Program Scientific Collaboration On Past Speciation Conditions in Lake Ohrid project cores recovered in spring–summer 2013, potentially dating back into the Lower Pleistocene, and will act as a recent calibration to reconstruct climate and hydrology over the entire lake history

Romidepsin Plus Cyclophosphamide, Doxorubicin, Vincristine, and Prednisone Versus Cyclophosphamide, Doxorubicin, Vincristine, and Prednisone in Patients With Previously Untreated Peripheral T-Cell Lymphoma: Final Analysis of the Ro-CHOP Trial.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.The primary analysis of the Ro-CHOP phase III randomized controlled trial (ClinicalTrials.gov identifier: NCT01796002) established that romidepsin (Ro) plus cyclophosphamide, doxorubicin, vincristine, prednisone (CHOP) did not yield an increased efficacy compared with CHOP alone as first-line treatment of peripheral T-cell lymphoma. We report the planned final analysis 5 years after the last patient enrolled. With a median follow-up of 6 years, median progression-free survival (PFS) was 12.0 months compared with 10.2 months (hazard ratio [HR], 0.79 [95% CI, 0.62 to 1.005]; P = .054), while median overall survival was 62.2 months (35.7-86.6 months) and 43.8 months (30.1-70.2 months; HR, 0.88 [95% CI, 0.68 to 1.14]; P = .324) in the Ro-CHOP and CHOP arms, respectively. In an exploratory analysis, the median PFS in the centrally reviewed follicular helper T-cell lymphoma subgroup was significantly longer in the Ro-CHOP arm (19.5 v 10.6 months, HR, 0.703 [95% CI, 0.502 to 0.985]; P = .039). Second-line treatments were given to 251 patients with a median PFS2 and OS2 after relapse or progression of 3.3 months and 11.5 months, respectively. Within the limits of highly heterogeneous second-line treatments, no specific regimen seemed to provide superior disease control. However, a potential benefit was observed with brentuximab vedotin in association with chemotherapy even after excluding anaplastic large-cell lymphoma subtype or after adjusting for histology and international prognostic index in a multivariate model (HR for PFS, 0.431 [95% CI, 0.238 to 0.779]; P = .005)