Impacts of extreme 2013–2014 winter conditions on Lake Michigan's fall heat content, surface temperature, and evaporation

Since the late 1990s, the Laurentian Great Lakes have experienced persistent low water levels and above average over‐lake evaporation rates. During the winter of 2013–2014, the lakes endured the most persistent, lowest temperatures and highest ice cover in recent history, fostering speculation that over‐lake evaporation rates might decrease and that water levels might rise. To address this speculation, we examined interseasonal relationships in Lake Michigan's thermal regime. We find pronounced relationships between winter conditions and subsequent fall heat content, modest relationships with fall surface temperature, but essentially no correlation with fall evaporation rates. Our findings suggest that the extreme winter conditions of 2013–2014 may have induced a shift in Lake Michigan's thermal regime and that this shift coincides with a recent (and ongoing) rise in Great Lakes water levels. If the shift persists, it could (assuming precipitation rates remain relatively constant) represent a return to thermal and hydrologic conditions not observed on Lake Michigan in over 15 years.Key PointsLake Michigan has been in an altered thermal regime since the late 1990sThe 2013–2014 winter may return Lake Michigan to pre‐1998 thermal conditionsHydrological impacts of the 2013–2014 cold winter remain unclearPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112001/1/grl52850.pd

Simulating Impacts of Precipitation on Ice Cover and Surface Water Temperature Across Large Lakes

Precipitation impacts on ice cover and water temperature in the Laurentian Great Lakes were examined using state‐of‐the‐art coupled ice‐hydrodynamic models. Numerical experiments were conducted for the recent anomalously cold (2014–2015) and warm (2015–2016) winters that were accompanied by high and low ice coverage over the lakes, respectively. The results of numerical experiments showed that snow cover on the ice, which is the manifestation of winter precipitation, reduced the total ice volume (or mean ice thickness) in all of the Great Lakes, shortened the ice duration, and allowed earlier warming of water surface. The reduced ice volume was due to the thermal insulation of snow cover. The surface albedo was also increased by snow cover, but its impact on the delay the melting of ice was overcome by the thermal insulation effect. During major snowstorms, snowfall over the open lake caused notable cooling of the water surface due to latent heat absorption. Overall, the sensible heat flux from rain in spring and summer was found to have negligible impacts on the water surface temperature. Although uncertainties remain in overlake precipitation estimates and model’s representation of snow on the ice, this study demonstrated that winter precipitation, particularly snowfall on the ice and water surfaces, is an important contributing factor in Great Lakes ice production and thermal conditions from late fall to spring.Plain Language SummarySnow and rain impact on ice cover and water temperature in large lakes were studied using a computational model for an example of the Laurentian Great Lakes. It was found that snow cover increased the reflection of solar radiation but at the same time prevented lake ice from the growing, resulting in less formation of ice and slightly earlier melting. The earlier ice melting also allowed earlier warming of the water surface in spring. Major snowstorms caused slight cooling in the water surface temperature because snowflakes absorbed heat when it touched the water surface to melt. On the other hand, warmer rain barely changed the water surface temperature during summer.Key PointsPrecipitation impacts on Great Lakes ice cover and water temperature were evaluated using a coupled ice‐hydrodynamic modelThe model results showed that snow cover on the ice reduced the net production of ice, which resulted in earlier decay of ice coverThe model results showed that snowfall cooled the water surface notably through latent heat absorption during stormsPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155461/1/jgrc23973.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155461/2/jgrc23973_am.pd

Cold Water and High Ice Cover on Great Lakes in Spring 2014

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108350/1/eost2014EO340001.pd

Relationships between growth, quality, and stocking within managed old-growth northern hardwoods

Abstract: An understanding of long-term growth dynamics is central to the development of sustainable uneven-aged silvicultural systems for northern hardwood forests in eastern North America. Of particular importance are quantitative assessments of the relationships between stocking control and long-term growth and quality development. This study examined these relationships in a long-term silviculture experiment established in northern hardwood stands in the Upper Peninsula of Michigan, USA. Stands were old growth at the onset of the experiment and were maintained at three residual stocking levels (11.5, 16.1, and 20.7 m 2 ·ha -1 ) over a 57-year period. Several aspects of long-term stocking control were evaluated, including the effects of residual stocking on tree quality development and the relationships between stand stocking and individual tree growth and stand-level production. Results suggest that residual stocking had little impact on quality development, likely due to the initial old-growth condition of the stands examined. In contrast, our results indicate that a range of stand densities will maintain acceptable rates of stand-level production in selection systems and that growth can be shifted between diameter classes depending on desired future stand conditions. Résumé : La compréhension de la dynamique de la croissance à long terme est essentielle pour mettre au point des systè-mes sylvicoles durables appliqués aux forêts inéquiennes de feuillus nordiques dans l'est de l'Amérique du Nord. Il est particulièrement important de quantifier les relations à long terme entre la surface terrière résiduelle et la croissance et le développement de la qualité. Cette étude se penche sur ces relations dans le cadre d'une expérience sylvicole de longue durée établie dans des peuplements de feuillus nordiques sur la péninsule supérieure du Michigan, aux États-Unis. Au début de l'expérience, la surface terrière de ces vieux peuplements a été abaissée à trois niveaux différents (11,5, 16,1 et 20,7 m 2 ·ha -1 ) qui ont été maintenus pendant une période de 57 ans. Plusieurs aspects du maintien de la surface terrière ont été évalués, dont l'effet de la surface terrière résiduelle sur le développement de la qualité des arbres et la relation entre la surface terrière et la croissance aux échelles de l'arbre individuel et du peuplement. Les résultats indiquent que la surface terrière résiduelle a eu peu d'impact sur le développement de la qualité, probablement parce que les peuplements étudiés étaient initialement des vieilles forêts. Par contre, nos résultats indiquent qu'une gamme de densités résiduelles est en mesure de maintenir des taux acceptables de production à l'échelle du peuplement dans les systèmes de jardinage et que la croissance peut être déplacée entre les classes de diamètre en fonction des conditions futures du peuplement que l'on désire. [Traduit par la Rédaction

Depression and anxiety in acute ischemic stroke involving the anterior but not paramedian or inferolateral thalamus

Background and objectives: Emotional and cognitive deficits are prevalent in strokes involving the thalamus. In contrast to cognitive deficits, emotional deficits have not been studied prospectively in isolated thalamic stroke. Methods: In 37 ischemic thalamic stroke patients (57.0 [50.0; 69.5] years [median (Q1; Q3)], 21 males, 5 anterior, 12 paramedian, 20 inferolateral vascular territory), and 37 non-stroke control patients matched for age and sex, we prospectively examined depression, anxiety, activities of daily living, and quality of life at 1, 6, 12, and 24 months post-stroke using the Hospital-Anxiety-and-Depression Scale (HADS), Nürnberger-Alters-Alltagsaktivitäten scale (NAA), and Short Form-36 (SF36) questionnaire. Voxel-based lesion-symptom mapping (VLSM) and lesion-subtraction analyzes were performed to determine associations between questionnaire scores and thalamic stroke topography. Results: At 1 month post-stroke, anterior thalamic stroke patients had higher depression scores [8.0 (7.5; 10.5)] than paramedian [4.5 (1.0; 5.8)] and inferolateral [4.0 (1.0; 7.0)] thalamic stroke patients. Furthermore, anterior thalamic stroke patients had higher anxiety scores [11.0 (8.0; 14.5)] than their matched controls [2.5 (2.0; 2.5)], paramedian [4.5 (1.0; 5.8)] and inferior [4.0 (1.0; 7.0)] thalamic stroke patients. Depression and anxiety scores in anterior thalamic stroke patients remained high across the follow-up [depression: 9.0 (3.5; 13,8); anxiety:10.05 (2.8, 14.5)]. Physical health assessed by SF36 was intact in anterior [1 month post-stroke: T-score = 55.9 (37.0; 57.6)] but reduced in inferolateral [44.5(32.4; 53.1)] thalamic stroke, whereas mental health was reduced in anterior thalamic stroke [32.0 (29.8; 47.3)]. VLSM confirmed that voxels in the anterior thalamus around Montreal Neurological Institute (MNI) coordinates X = −8, Y = −12, Z = 2 were more often affected by the stroke in depressed (HADS-score ≥ 8) than non-depressed (HADS-score < 8) patients and voxels around coordinates X = −10, Y = −12, Z = 2 were more often affected in anxious (HADS-score ≥ 8) than non-anxious (HADS-score < 8) patients. Conclusion: Anterior, but not paramedian or inferolateral thalamic stroke was associated with depression and anxiety. Even though our results are mostly significant in the left thalamus, this observation on stroke laterality might be confounded by the fact that the right hemisphere was underrepresented in our study

Radiative corrections to the Chern-Simons term at finite temperature in the noncommutative Chern-Simons-Higgs model

By analyzing the odd parity part of the gauge field two and three point vertex functions, the one-loop radiative correction to the Chern-Simons coefficient is computed in noncommutative Chern-Simons-Higgs model at zero and at high temperature. At high temperature, we show that the static limit of this correction is proportional to $T$ but the first noncommutative correction increases as $T\log T$. Our results are analytic functions of the noncommutative parameter.Comment: Revised version with a new section on the gauge field three point vertex function adde

Squark-, Slepton- and Neutralino-Chargino coannihilation effects in the low-energy effective MSSM

Within the low-energy effective Minimal Supersymmetric extension of the Standard Model (effMSSM) we calculate the neutralino relic density taking into account slepton-neutralino, squark-neutralino and neutralino/chargino- neutralino coannihilation channels. By including squark (stop and sbottom) coannihilation channels we extend our comparative study to all allowed coannihilations and obtain the general result that all of them give sizable contributions to the reduction of the neutralino relic density. Due to these coannihilation processes some models (mostly with large neutralino masses) enter into the cosmologically interesting region for relic density, but other models leave this region. Nevertheless, in general, the predictions for direct and indirect dark matter detection rates are not strongly affected by these coannihilation channels in the effMSSM.Comment: 14 pages, 10 figures, corrected and to be published in Phys. Rev.

Identification of the skeletal progenitor cells forming osteophytes in osteoarthritis.

OBJECTIVES: Osteophytes are highly prevalent in osteoarthritis (OA) and are associated with pain and functional disability. These pathological outgrowths of cartilage and bone typically form at the junction of articular cartilage, periosteum and synovium. The aim of this study was to identify the cells forming osteophytes in OA. METHODS: Fluorescent genetic cell-labelling and tracing mouse models were induced with tamoxifen to switch on reporter expression, as appropriate, followed by surgery to induce destabilisation of the medial meniscus. Contributions of fluorescently labelled cells to osteophytes after 2 or 8 weeks, and their molecular identity, were analysed by histology, immunofluorescence staining and RNA in situ hybridisation. Pdgfrα-H2BGFP mice and Pdgfrα-CreER mice crossed with multicolour Confetti reporter mice were used for identification and clonal tracing of mesenchymal progenitors. Mice carrying Col2-CreER, Nes-CreER, LepR-Cre, Grem1-CreER, Gdf5-Cre, Sox9-CreER or Prg4-CreER were crossed with tdTomato reporter mice to lineage-trace chondrocytes and stem/progenitor cell subpopulations. RESULTS: Articular chondrocytes, or skeletal stem cells identified by Nes, LepR or Grem1 expression, did not give rise to osteophytes. Instead, osteophytes derived from Pdgfrα-expressing stem/progenitor cells in periosteum and synovium that are descendants from the Gdf5-expressing embryonic joint interzone. Further, we show that Sox9-expressing progenitors in periosteum supplied hybrid skeletal cells to the early osteophyte, while Prg4-expressing progenitors from synovial lining contributed to cartilage capping the osteophyte, but not to bone. CONCLUSION: Our findings reveal distinct periosteal and synovial skeletal progenitors that cooperate to form osteophytes in OA. These cell populations could be targeted in disease modification for treatment of OA

A Minimal Threshold of c-di-GMP Is Essential for Fruiting Body Formation and Sporulation in Myxococcus xanthus

Generally, the second messenger bis-(3’-5’)-cyclic dimeric GMP (c-di-GMP) regulates the switch between motile and sessile lifestyles in bacteria. Here, we show that c-di-GMP is an essential regulator of multicellular development in the social bacterium Myxococcus xanthus. In response to starvation, M. xanthus initiates a developmental program that culminates in formation of spore-filled fruiting bodies. We show that c-di-GMP accumulates at elevated levels during development and that this increase is essential for completion of development whereas excess c-di-GMP does not interfere with development. MXAN3735 (renamed DmxB) is identified as a diguanylate cyclase that only functions during development and is responsible for this increased c-di-GMP accumulation. DmxB synthesis is induced in response to starvation, thereby restricting DmxB activity to development. DmxB is essential for development and functions downstream of the Dif chemosensory system to stimulate exopolysaccharide accumulation by inducing transcription of a subset of the genes encoding proteins involved in exopolysaccharide synthesis. The developmental defects in the dmxB mutant are non-cell autonomous and rescued by co-development with a strain proficient in exopolysaccharide synthesis, suggesting reduced exopolysaccharide accumulation as the causative defect in this mutant. The NtrC-like transcriptional regulator EpsI/Nla24, which is required for exopolysaccharide accumulation, is identified as a c-diGMP receptor, and thus a putative target for DmxB generated c-di-GMP. Because DmxB can be—at least partially—functionally replaced by a heterologous diguanylate cyclase, these results altogether suggest a model in which a minimum threshold level of c-di-GMP is essential for the successful completion of multicellular development in M. xanthus

Evaluating and improving modeled turbulent heat fluxes across the North American Great Lakes

Turbulent fluxes of latent and sensible heat are important physical processes that influence the energy and water budgets of the North American Great Lakes. These fluxes can be measured in situ using eddy covariance techniques and are regularly included as a component of lake–atmosphere models. To help ensure accurate projections of lake temperature, circulation, and regional meteorology, we validated the output of five algorithms used in three popular models to calculate surface heat fluxes: the Finite Volume Community Ocean Model (FVCOM, with three different options for heat flux algorithm), the Weather Research and Forecasting (WRF) model, and the Large Lake Thermodynamic Model. These models are used in research and operational environments and concentrate on different aspects of the Great Lakes' physical system. We isolated only the code for the heat flux algorithms from each model and drove them using meteorological data from four over-lake stations within the Great Lakes Evaporation Network (GLEN), where eddy covariance measurements were also made, enabling co-located comparison. All algorithms reasonably reproduced the seasonal cycle of the turbulent heat fluxes, but all of the algorithms except for the Coupled Ocean–Atmosphere Response Experiment (COARE) algorithm showed notable overestimation of the fluxes in fall and winter. Overall, COARE had the best agreement with eddy covariance measurements. The four algorithms other than COARE were altered by updating the parameterization of roughness length scales for air temperature and humidity to match those used in COARE, yielding improved agreement between modeled and observed sensible and latent heat fluxes.</p