Initial Warming Research Articles

A coherent response of Southern Indian Ocean to the Antarctic climate: Implications to the lead, lags of atmospheric CO2 during deglaciation

A record of δ18Oc from the Indian sector of Southern Ocean and atmospheric CO2, and δ18O of European Project for Ice Coring in Antarctica (EPICA) and Greenland Ice Sheet Project 2 (GISP2) reveals that a coherent response between δ18O record of Antarctic ice core and the δ18Oc record from Southern Indian Ocean during the deglaciation with initial warming starting around 18 kyr BP which is in agreement with the raise of atmospheric CO2 during same time. A distinct asynchrony between the records of δ18Oc from the Southern Indian Ocean and δ18O of GISP2 during the last deglaciation is noticed. We report that Southern Ocean degassing played an important role in raising atmospheric CO2 through Atlantic Meridional Overturning Circulation (AMOC), which has an implication in triggering abrupt climate events through coupling of ocean and atmospheric processes.

Multiple vitrification-warming and biopsy procedures on human embryos: clinical outcome and neonatal follow-up of children.

Does double vitrification and warming of human blastocysts having undergone biopsy once or twice have an impact on the clinical outcome? The clinical pregnancy rate obtained with double vitrification single biopsy blastocysts was comparable to that obtained with single vitrification single biopsy blastocysts in our center in the same time period (46%; 2016-2018), whereas that obtained with double-vitrified double-biopsied blastocysts seemed lower and will need further study. Genetic testing on cryopreserved unbiopsied embryos involves two cryopreservation procedures. Retesting of failed/inconclusive-diagnosed blastocysts inevitably involves a second round of biopsy and a second round of vitrification as well. To what extent this practice impacts on the developmental potential of blastocysts has been studied to a limited extent so far and holds controversy. Additionally, the obstetrical/perinatal outcome after the transfer of double-vitrified/single or double-biopsied blastocysts is poorly documented. This retrospective observational study included 97 cycles of trophectoderm biopsy and preimplantation genetic testing (PGT) on vitrified-warmed embryos followed by a second round of vitrification between March 2015 and December 2019. In 36 warming cycles, no biopsy was performed on the embryos before the first vitrification (single biopsy group). In 61 warming cycles, the embryos had been biopsied on Day 3 (n = 4) or on Day 5/6 (n = 57) before the first vitrification (double biopsy group). A second biopsy was mostly indicated in cycles of failed or inconclusive diagnosis at the first biopsy. Two cycles involved a more specific mutation test for X-linked diseases on male embryos and one cycle involved testing for a second monogenic indication supplementary to a previously tested reciprocal translocation. Post-warming suitability for biopsy, availability of genetically transferable embryos and clinical outcome of subsequent frozen-thawed embryo transfer (FET) cycles were reported. Neonatal follow-up of the children was included. In total, 91 cleavage-stage embryos and 154 blastocysts were warmed, of which 34 (37.4%) and 126 (81.8%), respectively, were of sufficient quality to undergo trophectoderm biopsy and were subsequently vitrified for a second time. Out of these, 92 underwent biopsy for the first time (single biopsy), whereas 68 underwent a second biopsy (double biopsy). After diagnosis, 77 blastocysts (48.1%) were revealed to be genetically transferable (44 in the single biopsy group and 33 in the double biopsy group). In 46 warming cycles, 51 blastocysts were warmed and 49 survived this second warming procedure (96.0%). Subsequently, there were 45 FET cycles resulting in 27 biochemical pregnancies and 18 clinical pregnancies with fetal heartbeat (40.0% per FET cycle: 44.0% in the single biopsy group and 35.0% in the double biopsy group, P = 0.54). Thirteen singletons were born (eight in the single biopsy group and five in the double biopsy group), while three pregnancies were ongoing. A total of 26 embryos (13 in each group) remain vitrified and have the potential to increase the final clinical pregnancy rate. The neonatal follow-up of the children born so far is reassuring. This is a small retrospective cohort, thus, the implantation potential of double vitrification double biopsy blastocysts, as compared to double vitrification single biopsy blastocysts and standard PGT (single vitrification, single biopsy), certainly needs further investigation. Although one could speculate on birthweight being affected by the number of biopsies performed, the numbers in this study are too small to compare birthweight standard deviation scores in singletons born after single or double biopsy. PGT on vitrified-warmed embryos, including a second vitrification-warming step, results in healthy live birth deliveries, for both single- and double-biopsied embryos. The neonatal follow-up of the 13 children born so far did not indicate any adverse effect. The present study is important in order to provide proper counseling to couples on their chance of a live birth per initial warming cycle planned and concerning the safety issue of rebiopsy and double vitrification. None. N/A.

Summer temperature development 18,000–14,000 cal. BP recorded by a new chironomid record from Burgäschisee, Swiss Plateau

The termination of the Last Ice Age after the Last Glacial maximum (LGM) represents a dynamic period in the history of the circum-north Atlantic region. So far, there are few reliably dated climatic reconstructions covering the Lateglacial period prior to 14,700 cal. BP in Central and Northern Europe. We present a new chironomid record for the period 18,000–14,000 cal. BP, from Burgäschisee, Switzerland. Chironomid assemblages immediately following glacier retreat were dominated by taxa indicative of cold, oligotrophic conditions such as Sergentia coracina -type and Micropsectra radialis -type. A gradual transition to assemblages with moderate abundances of taxa indicative of warmer climatic conditions such as Dicrotendipes nevosus -type and Tanytarsus glabrescens -type started after ca. 16,100 cal. BP. This initial and gradual chironomid assemblage shift culminated in a more pronounced and rapid inferred temperature change at the Oldest Dryas/Bølling transition at ca. 14,700 cal. BP, where further types indicative of warm conditions such as Tanytarsus lactescens -type first occurred and replaced chironomids indicative of colder conditions such as Paracladius and Protanypus. We estimated past July air temperature changes from the chironomid assemblages by applying to the record a chironomid-temperature transfer function that is based on chironomid distribution data from 274 lakes in Switzerland and Norway. The resulting reconstruction, which features a sample-specific root mean square error of prediction of 1.36–1.46 °C, indicates temperatures around 9 °C at the beginning of the record. An initial gradual warming phase initiating at ca. 16,100 cal. BP is recorded reaching values around 10 °C for the period 16,100–15,500 cal. BP. Temperatures continue to increase reaching values around 12 °C for the period preceding the Bølling warming, when temperatures rose rapidly to values around 15 °C. The early temperature rise to values of 10–12 °C prior to the Bølling warming agrees with widespread vegetation changes recently reported for this region based on palaeobotanical analyses, which indicate a shift from herbaceous tundra to shrub tundra with low density tree birch stands with open canopies. Together, these results suggest an earlier Lateglacial temperature increase in southwest Central Europe than expected based on earlier palaeobotanical reconstructions, although with a less pronounced warming than has been reported for ca. 16,000 cal. BP from south of the Alps. This early Lateglacial warming agrees with glacier reconstructions which suggest several step-wise reductions of glacier extent in this period as well as with evidence from other palaeotemperature reconstructions and suggests that not only Southern Europe but significant parts of Europe north of the Alps may have been characterized by early Lateglacial warming well before the rapid warming at ca. 14,700 cal. BP.

Polar Phasing and Cross‐Equatorial Heat Transfer Following a Simulated Abrupt NH Warming of a Glacial Climate

AbstractA 150‐ to 220‐year lag between abrupt Greenland warming and maximum Antarctic warming characterizes past glacial Dansgaard‐Oeschger events. In a modeling study, we investigate how the cross‐equatorial oceanic heat transport (COHT) might drive this phasing during an abrupt Northern Hemisphere (NH) warming. We use the MITgcm in an idealized continental configuration with two ocean basins, one wider, one narrower, under glacial‐like conditions with sea ice reaching midlatitudes. An exaggerated eccentricity‐related solar radiation anomaly is imposed over 100 years to trigger an abrupt NH warming and sea‐ice melting. The Hadley circulation shifts northward in response, weakening the NH trade winds, subtropical cells, and COHT in both ocean basins. This induces heat convergence in the Southern Hemisphere (SH) ocean subsurface, from where upward heat release melts sea ice and warms SH high latitudes. Although the small‐basin meridional overturning circulation also weakens, driven by NH ice melting, it contributes at most one‐third to the total COHT anomaly, hence playing a subsidiary role in the SH and NH initial warming. Switching off the forcing cools the NH; yet heat release continues from the SH ocean subsurface via isopycnal advection‐diffusion and vertical mixing, driving further sea ice melting and high latitude warming for ~50–70 more years. A phasing in polar temperatures resembling reconstructions thus emerges, linked to changes in the subtropical cells’ COHT, and SH ocean heat storage and surface fluxes. Our results highlight the potential role of the atmosphere circulation and wind‐driven global ocean circulation in the NH–SH phasing seen in DO events.

Physical Diagnosis of the 2016 Great Barrier Reef Bleaching Event

AbstractWidespread coral bleaching across the Great Barrier Reef (GBR) in 2016 is often reportedly caused by El Niño and/or global warming. However, the GBR is not in a region where it is straightforward to anticipate sea surface temperature (SST) warming during El Niño, and the role of climate change is unclear. This study uses a diverse range of observations to investigate the physical causes of SST anomalies that developed on the GBR in 2016. Warm SST anomalies developed in two stages. Initial warming was caused by El Niño shifting the global‐scale pattern of convection, increasing solar radiation in the Coral Sea. The warm anomaly was extended and amplified near the coast by a terrestrial heat wave propagating across eastern Australia, further warming the GBR through turbulent heat flux. It is concluded that El Niño caused the SST anomaly, and global warming increased its amplitude and extended it by several months.

Modelling past and future peatland carbon dynamics across the pan-Arctic.

The majority of northern peatlands were initiated during the Holocene. Owing to their mass imbalance, they have sequestered huge amounts of carbon in terrestrial ecosystems. Although recent syntheses have filled some knowledge gaps, the extent and remoteness of many peatlands pose challenges to developing reliable regional carbon accumulation estimates from observations. In this work, we employed an individual- and patch-based dynamic global vegetation model (LPJ-GUESS) with peatland and permafrost functionality to quantify long-term carbon accumulation rates in northern peatlands and to assess the effects of historical and projected future climate change on peatland carbon balance. We combined published datasets of peat basal age to form an up-to-date peat inception surface for the pan-Arctic region which we then used to constrain the model. We divided our analysis into two parts, with a focus both on the carbon accumulation changes detected within the observed peatland boundary and at pan-Arctic scale under two contrasting warming scenarios (representative concentration pathway-RCP8.5 and RCP2.6). We found that peatlands continue to act as carbon sinks under both warming scenarios, but their sink capacity will be substantially reduced under the high-warming (RCP8.5) scenario after 2050. Areas where peat production was initially hampered by permafrost and low productivity were found to accumulate more carbon because of the initial warming and moisture-rich environment due to permafrost thaw, higher precipitation and elevated CO2 levels. On the other hand, we project that areas which will experience reduced precipitation rates and those without permafrost will lose more carbon in the near future, particularly peatlands located in the European region and between 45 and 55°N latitude. Overall, we found that rapid global warming could reduce the carbon sink capacity of the northern peatlands in the coming decades.

Three-dimensional thermo-hydro-mechanical coupled modeling of thermal anomalies before the 2008 Wenchuan earthquake

Pre-seismic thermal anomalies have been widely reported, however, there is still no unified understanding of their causes or physical mechanisms. To clarify whether subsurface fluid convection and rock deformation directly related to seismic fault stress release can form thermal anomalies before an earthquake, we carried out thermo-hydro-mechanical (THM) coupled modeling of the Wenchuan earthquake, and considered the influence of maximum horizontal principal stress direction (MPSD) and fault dip. The results show that convective thermal flux (CT) anomalies of subsurface fluid and the deformation induced thermal flux (DT) of the rock mass caused by stress release of the seismic fault can explain the observed thermal anomalies along the fault. The calculated and observed thermal anomalies are comparable in spatial distribution, evolution, and magnitude. Specifically, for the Wenchuan earthquake, seismic fault stress release-induced CT and DT anomalies occur in the fault zone and in the adjacent hanging wall area. In the fault zone, CT and DT induced thermal anomalies were comparable, and superposition of the two was characterized by strong initial warming, followed by weaker warming and then short-term cooling. However, outside of the fault zone, CT induced thermal anomalies had much higher intensities than those induced by DT, and were characterized by band-like warming along the hanging wall of the fault. In addition, variations in the MPSD and fault dip cause the segmentation of thermal anomalies along the Wenchuan earthquake fault. From the southern to the northern segments of the fault, the intensity of thermal anomalies is significantly weakened with rotation of MPSD and an increase in fault dip. Our study provides evidence that seismic fault stress release is the cause of pre-seismic thermal anomalies; furthermore, the results indicate the CT and DT could be important physical mechanisms of pre-seismic thermal anomalies.

West Antarctic ice sheet and CO2 greenhouse effect: a threat of disaster

ABSTRACT Over 40 years ago, the glaciologist John Mercer warned that parts of the West Antarctic Ice Sheet were at risk of collapse due to the CO2 greenhouse effect. Mercer recognised the unique vulnerability of ice sheets resting on beds far below sea level (marine-based ice sheets), where an initial warming signal can initiate irreversible retreat. In this paper, we review recent work on evidence for ice sheet collapse in warmer periods of the recent geological past, the current behaviour of the ice sheet, and computer models used to predict future ice-sheet response to global warming. Much of this work points in the same direction: warming climates can indeed trigger collapse of marine-based portions of the West Antarctic Ice Sheet, and retreat in response to recent warming has brought parts of the ice sheet to the threshold of instability. Further retreat appears to be inevitable, but the rate of collapse depends critically on future emissions.

How Do Ocean Warm Anomalies Favor the Aggregation of Deep Convective Clouds?

AbstractWe investigate the role of a warm sea surface temperature (SST) anomaly (hot spot of typically 3 to 5 K) on the aggregation of convection using cloud-resolving simulations in a nonrotating framework. It is well known that SST gradients can spatially organize convection. Even with uniform SST, the spontaneous self-aggregation of convection is possible above a critical SST (here 295 K), arising mainly from radiative feedbacks. We investigate how a circular hot spot helps organize convection, and how self-aggregation feedbacks modulate this organization. The hot spot significantly accelerates aggregation, particularly for warmer/larger hot spots, and extends the range of SSTs for which aggregation occurs; however, at cold SST (290 K) the aggregated cluster disaggregates if we remove the hot spot. A large convective instability over the hot spot leads to stronger convection and generates a large-scale circulation which forces the subsidence drying outside the hot spot. Indeed, convection over the hot spot brings the atmosphere toward a warmer temperature. The warmer temperatures are imprinted over the whole domain by gravity waves and subsidence warming. The initial transient warming and concomitant subsidence drying suppress convection outside the hot spot, thus driving the aggregation. The hot-spot-induced large-scale circulation can enforce the aggregation even without radiative feedbacks for hot spots sufficiently large/warm. The strength of the large-scale circulation, which defines the speed of aggregation, is a function of the hot spot fractional area. At equilibrium, once the aggregation is well established, the moist convective region with upward midtropospheric motion, centered over the hot spot, has an area surprisingly independent of the hot spot size.

Spatiotemporal variability and decadal trends of snowmelt processes on Antarctic sea ice observed by satellite scatterometers

Abstract. The timing and intensity of snowmelt processes on sea ice are key drivers determining the seasonal sea-ice energy and mass budgets. In the Arctic, satellite passive microwave and radar observations have revealed a trend towards an earlier snowmelt onset during the last decades, which is an important aspect of Arctic amplification and sea-ice decline. Around Antarctica, snowmelt on perennial ice is weak and very different than in the Arctic, with most snow surviving the summer. Here we compile time series of snowmelt onset dates on seasonal and perennial Antarctic sea ice from 1992 to 2014/15 using active microwave observations from the European Space Agency's (ESA) European Remote Sensing (ERS) 1 and 2 missions (ERS-1 and ERS-2), Quick Scatterometer (QSCAT), and Advanced Scatterometer (ASCAT) radar scatterometers. We define two snowmelt transition stages: a weak backscatter rise, indicating the initial warming and destructive metamorphism of the snowpack (pre-melt), followed by a rapid backscatter rise, indicating the onset of thaw–freeze cycles (snowmelt). Results show large interannual variability, with an average pre-melt onset date of 29 November and melt onset of 10 December, respectively, on perennial ice, without any significant trends over the study period, consistent with the small trends of Antarctic sea-ice extent. There was a latitudinal gradient from early snowmelt onsets in mid-November in the northern Weddell Sea to late (end of December) or even absent snowmelt conditions in the southern Weddell Sea. We show that QSCAT Ku-band-derived (13.4 GHz signal frequency) pre-melt and snowmelt onset dates are earlier by 20 and 18 d, respectively, than ERS and ASCAT C-band-derived (5.6 GHz) dates. This offset has been considered when constructing the time series. Snowmelt onset dates from passive microwave observations (37 GHz) are later by 14 and 6 d than those from the scatterometers, respectively. Based on these characteristic differences between melt onset dates observed by different microwave wavelengths, we developed a conceptual model which illustrates how the seasonal evolution of snow temperature profiles may affect different microwave bands with different penetration depths. These suggest that future multi-frequency active and passive microwave satellite missions could be used to resolve melt processes throughout the vertical snow column of thick snow on perennial Antarctic sea ice.

Дослідження процесу пропарювання букових заготовок і пиломатеріалів

Зменшити втрати деревини від грибкових пошкоджень під час зберігання і транспортування можна завдяки проведенню теплової стерилізації. Теплову обробку деревини використовують у багатьох деревообробних процесах: виробництво лущеного і струганого шпону, у лісопильному виробництві, процесах гнуття та пресування. Одним із видів теплової обробки деревини є пропарювання. Відсутність процесу пропарювання букових пиломатеріалів після лісопилення є причиною значних втрат деревини від розтріскування, враження грибами та комахами. У виробничих умовах, під час пропарювання, не враховують багато чинників: особливостей будови деревини бука, її густини, теплових та механічних властивостей. Все це призводить до зайвих втрат матеріалу, теплової енергії та якісних показників букових пиломатеріалів. Тому дуже важливо досліджувати режими та технології пропарювання букових пиломатеріалів із збереженням їх фізико-механічних властивостей. Дослідження проведено з використанням пропарювального ковпака виробничого зразка. Здійснено експериментальні дослідження пропарювання букових заготовок та пиломатеріалів, яке охоплює початковий прогрів, сам процес пропарювання та охолодження. Внаслідок проведення експериментальних досліджень вибрано оптимальні режими пропарювання, які зберігають якісні фізико-механічні показники, такі як: запобігання втратам деревини під час зберігання і транспортування, вирівнювання забарвлення або надання деревині потрібного кольору, покращення міцності та пластичності, прискорення подальшого сушіння.

Changes of MJO propagation characteristics under global warming

The change of Madden–Julian Oscillation (MJO) propagation and periodicity characteristics under global warming is investigated using two selected CMIP5 models. It is found that the MJO period tends to be shorter, while its eastward propagation tends to be accelerated. Meanwhile the main MJO activity center shifts eastward toward the central equatorial Pacific. Two factors are possibly responsible for the increased eastward phase speed of the MJO. The first is attributed to the increase of atmospheric static stability that accelerates equatorial Kelvin wave speed. The second is attributed to the increase of zonal asymmetry of MJO-scale moist static energy (MSE) tendency, which is contributed to the combined effect of anomalous circulation and mean MSE gradient. A theoretical framework is constructed to understand the relative role of anomalous heating and mean static stability changes in determining MJO-scale circulation change. It is found that their effect is phase dependent. During the initial warming phase the circulation change is primarily controlled by the heating change, whereas during the later warming phase it is primarily controlled by the static stability change. The eastward shift of the main MJO activity center is possibly caused by the occurrence of an El Nino-like mean SST change and associated vertical overturning circulation change in the tropical Pacific.

Linking the North American Dipole to the Pacific Meridional Mode

AbstractThe North American dipole (NAD) represents a meridional dipole of sea level pressure anomalies over the western tropical North Atlantic and northeastern North America. This study demonstrates that the NAD is intimately linked to the development of the Pacific meridional mode (PMM). In addition to the North Pacific Oscillation, the NAD provides another important remote forcing source to trigger the PMM. The NAD influences the PMM through both direct and indirect pathways. The direct effect is that the winter NAD influences the sea surface temperature (SST) and surface winds over the northeastern subtropical Pacific (NESP) through concurrent anticyclonic flow associated with the NAD, which tends to generate a weak initial warming over the NESP region during late winter and early spring. The indirect effect is that the NAD first induces SST cooling over the northern tropical Atlantic during spring, and the northern tropical Atlantic SST cooling then generates a low‐level anticyclonic flow anomaly over the NESP, which further strengthens the surface warming over the NESP, thereby causing the development of the PMM in the following months. The NAD can also exert an influence on the El Niño–Southern Oscillation through its effects on the PMM. In particular, El Niño episodes led by the combined NAD‐PMM events tend to take the form of the central Pacific El Niño, rather than the canonical eastern Pacific El Niño. We suggest that a better understanding of the NAD‐PMM‐El Niño–Southern Oscillation dynamic link could be useful for the prediction of different types of El Niño event.

The transient response of atmospheric and oceanic heat transports to anthropogenic warming

Model projections of the near-future response to anthropogenic warming show compensation between meridional heat transports by the atmosphere (AHT) and ocean (OHT) that are largely symmetric about the equator1–3, the causes of which remain unclear. Here, using both the Coupled Model Intercomparison Project Phase 5 archive and Community Climate System Model version 4 simulations forced with Representative Concentration Pathway 8.5 to 2600, we show that this transient compensation—specifically during the initial stage of warming—is caused by combined changes in both atmospheric and oceanic circulations. In particular, it is caused by a southward OHT associated with a weakened Atlantic Meridional Overturning Circulation, a northward apparent OHT associated with an ocean heat storage maximum around the Southern Ocean, and a symmetric coupled response of the Hadley and Subtropical cells in the Indo-Pacific basin. It is further shown that the true advective OHT differs from the flux-inferred OHT in the initial warming due to the inhomogeneous responses of ocean heat storage. These results provide new insights to further our understanding of future heat transport responses, and thereby global climatic processes such as the redistribution of ocean heat. The compensation between atmospheric and oceanic heat transports under anthropogenic warming can be linked to the combined impact of Atlantic Meridional Overturning Circulation weakening, perturbations to Southern Ocean heat storage, and coupled responses of the Hadley and Subtropical cells.

New constraints on massive carbon release and recovery processes during the Paleocene-Eocene Thermal Maximum

Recent geochemical and sedimentological evidence constrains the response of seawater chemistry to carbon injection during the Paleocene-Eocene Thermal Maximum (PETM): foraminiferal boron-based proxy records constrain the magnitude and duration of surface ocean acidification, while new deep sea records document a carbonate compensation depth (CCD) over-shoot during the recovery. Such features can be used to more tightly constrain simulations of the event within carbon cycle models, and thus test mechanisms for carbon release, buffering, and sequestration. We use the LOSCAR carbon cycle model to examine first the onset of, and then recovery from the PETM. We systematically varied the mass, rate, and location of C release along with changes in ocean circulation patterns as well as initial conditions such as pre-event pCO2 and the strength of weathering feedbacks. A range of input parameters produced output that successfully conformed to observational constraints on the event’s onset. However, none of the successful scenarios featured surface seawater aragonite or calcite undersaturation at even peak PETM conditions (in contrast to anthropogenic acidification projections), and most runs featured approximately a doubling of pCO2 relative to pre-event conditions (suggesting a high PETM climate sensitivity). Further runs test scenarios of the body and recovery of the PETM against records of sustained acidification followed by rapid pH recovery in boron records, as well as the timing and depth of the CCD overshoot. Successful scenarios all require a sustained release of carbon over many tens of thousands of years following the onset (comparable to the mass released during the onset) and removal of carbon (likely as burial of organic carbon in addition to elevated chemical weathering rates) during the recovery. This sequence of events is consistent with a short-lived feedback involving the release of 13C-depleted C in response to initial warming followed by its subsequent sequestration during the cooling phase.

Раціональне тепловикористання в сучасних сушильних камерах

Обґрунтовано деякі особливості раціонального тепловикористання в сучасних сушильних камерах, які часто використовують у промисловості та сільському господарстві. Об'єктом сушіння при цьому є як сировина – дошки, заготовки, паркетна фриза, так і напівфабрикати – лущений або струганий шпон, подрібнена деревина, а також готові вироби – фанера, стільці, крісла тощо. Проаналізовано процеси сушіння за кривими зміни середньої вологості матеріалу (об'єкта сушіння) в часі (так звані "криві сушіння") і зміни температури (криві), а також швидкості зміни вологості в часі. Встановлено, що висушування різних матеріалів за різних способів підведення до них тепла (конвекції, терморадіації, кондукції) під час постійних режимних параметрів складається із трьох періодів сушіння (періоду початкового прогрівання, періодів постійної та сповільнювальної швидкостей сушіння). Однак проблема зменшення енергетичних витрат на сушіння деревини залишається сталою, позаяк не здійснюється раціональне тепловикористання, а також мало використовуються сучасні способи та засоби інтенсифікації процесу сушіння деревини. Тому створення сучасного обладнання, що дає змогу вирішити цю проблему, – основна мета цієї роботи. Також розглянуто концепцію тепловикористання під час розроблення конструкцій сушильних камер для зменшення питомих витрат теплової енергії. Запропоновано деяку комбінацію методів визначення показників камери із складанням основних показників затрат теплової енергії, що витрачається на сушіння пиломатеріалів.

South Atlantic Forced Multidecadal Teleconnection to the Midlatitude South Indian Ocean

AbstractSea surface temperature (SST) in the midlatitude south Indian Ocean (MSIO) exhibits prominent multidecadal fluctuations that have profound climate impacts for regions around the Indian Ocean. Observational analysis suggests that these multidecadal fluctuations can be explained by remote forcing from South Atlantic multidecadal variability. A suite of Atlantic Pacemaker experiments performs well in reproducing the observed MSIO SST multidecadal variation and its association with the South Atlantic. This transbasin covariability can be described by an atmospheric bridge mechanism, in which South Atlantic multidecadal variability‐related SST warming weakens regional meridional circulation over the South Atlantic, suppressing convection over tropical Africa. The reduced diabatic heating then drives a cold atmospheric Kelvin wave that penetrates into the tropical Indian Ocean, leading to an anomalous cyclonic circulation there that weakens the westerlies over the MSIO and subsequently triggers the warming of MSIO. This initial warming is further amplified by local SST‐water vapor positive feedback over the MSIO.

Air temperature feedback and its contribution to global warming

Air temperature feedback results from the thermal-radiative coupling between the atmosphere and the surface and plays an important role in surface energy balance. This paper reveals the contribution of air temperature feedback to the global warming from 1980 to 2000. The air temperature feedback kernel, evaluated using the ERA-Interim reanalysis data, is used to discuss the physical mechanism for air temperature feedback, the dependency of the strength of air temperature feedback on the climatological spatial distributions of air temperature, water vapor and cloud content, and the contributions of air temperature feedback to rapid global warming. The coupling between temperature feedback and each of the external forcings and individual feedback processes will amplify the anomaly of direct energy flux convergence at the surface induced by the external forcings and individual processes. The air temperature feedback amplifies the initial surface warming due to the increase in CO2 concentration, ice and snow melting, increase in water vapor, and change in ocean heat storage. It also amplifies the surface warming due to the longwave radiaitve forcing associated with the increase in cloud cover, which acts to suppress the cooling of the shortwave effect of cloud forcing. Overall, temperature feedback plays an important role in the global warming from 1980 to 2000, as the net positive contribution to the perturbation of global mean energy flux at the surface from the air temperature feedback is larger than the net negative contribution from external forcing and all non-temperature feedbacks.

Dead Sea pollen provides new insights into the paleoenvironment of the southern Levant during MIS 6–5

The paleoclimate of the southern Levant, especially during the last interglacial (LIG), is still under debate. Reliable paleovegetation information for this period, as independent evidence to the paleoenvironment, was still missing. In this study, we present a high-resolution pollen record encompassing 147–89 ka from the Dead Sea deep drilling core 5017-1A. The sediment profile is marked by alternations of laminated marl deposits and thick massive halite, indicating lake-level fluctuations. The pollen record suggests that steppe and desert components predominated in the Dead Sea surroundings during the whole investigated interval. The late penultimate glacial (147.3–130.9 ka) and early last glacial (115.5–89.1 ka) were cool and relatively dry, with sub-humid conditions confined to the mountains that sustained moderate amounts of deciduous oaks. Prior to the LIG optimum, a prevalence of desert components and a concomitant increase in frost-sensitive pistachio trees demonstrate the occurrence of an arid initial warming phase (130.9–124.2 ka). The LIG optimum (124.2 ka–115.5 ka) was initiated by an abrupt grass expansion that was followed by a rapid spread of woodlands in the mountains due to increased moisture availability. The remarkable sclerophyllous expansion points to a strong seasonal moisture deficit. These results contradict previous Dead Sea lake-level investigations that suggested pluvial glacials and a warm, dry LIG in the southern Levant. Prominent discrepancies between vegetation and Dead Sea lake stands are also registered at 128–115 ka, and the potential causes are discussed. In particular, while the pollen spectra mirror increased effective moisture during the LIG optimum, the massive halite deposition is indicative of an extremely low lake level. Given that the climate amelioration triggered the migration of early modern humans to the southern Levant, we speculate that the diverse ecosystems in the region provided great potential for their residence. Across the eastern Mediterranean region, an analogous vegetation succession pattern is observed.

Eventual re-vitrification or storage in liquid nitrogen vapor does not jeopardize the practical handling and transport of vitrified pig embryos

This study aimed (1) to evaluate the in vitro post-warming survival of porcine embryos after re-vitrification and (2) to assess the efficacy of transport of embryos in dry shipper (DS) in maintaining the viability and quality of vitrified embryos for a 3-day period. Embryos at the compacted or cavitating morula (CCM) and unhatched blastocyst (UBL) stages were surgically obtained from weaned, crossbred sows. In the first experiment, more than 85% of the embryos survived an initial vitrification and warming and achieved comparable survival rates to those of their fresh counterparts. In contrast, those embryos subjected to a second vitrification and warming had clearly lower survival rates (60% and 64% for re-vitrified embryos from the CCM and UBL groups, respectively) compared to the survival rates of the initial vitrification and fresh control groups (P < 0.01). Hatching rates were similar in re-vitrified blastocysts derived from vitrified CCMs and fresh control groups (50.8% and 55.3%, respectively). However, differences (P < 0.01) in hatching rates were recorded in re-vitrified blastocysts derived from vitrified UBLs and fresh control blastocysts (14.7% and 90.0%, respectively). In the second experiment, vitrified embryos were stored in a liquid nitrogen tank for one month. Then, the straws containing the embryos were transferred to a DS (DS group) or to another liquid nitrogen tank (control group) for an additional three days. Embryos from the DS and control groups had similar survival and hatching rates, regardless of the embryonic stage considered. The DS storage of CCMs and UBLs did not affect their development after culturing, including total cell numbers, compared to the control, although their apoptotic index was slightly higher (P < 0.05), regardless of the developmental stage. In conclusion, although re-vitrification negatively affects embryo survival, this study demonstrated that >60% of vitrified embryos could be successfully re-vitrified and re-warmed. The present study also showed the effectiveness of the DS for the storage of vitrified porcine CCMs and UBLs for at least three 3 days.