This study assessed the intrapersonal and interpersonal functioning of a three-couple expedition group that included a 2 1/2-year-old child which was ice-locked on a boat in the High Arctic during a major portion of the expedition. Personality assessment indicated that team members were generally well adjusted, scoring relatively higher on well-being and achievement and relatively lower on stress reactivity. Weekly mood ratings showed that the group exhibited significantly higher positive than negative affect. Reported negative events were relatively most frequent at the beginning of the Arctic stay and toward the end of the darkness period and were lowest during the initial darkness interval. The period of darkness had both a salutary and negative impact. A highly important means of coping with stress was seeking emotional support from one's partner. Selection of couples with strong bonds with their partner appears to be one viable approach for crew selection for long-duration missions.
This paper combines the data sets available today for 14C-age calibration of the last 60 ka. By stepwise synchronization of paleoclimate signatures, each of these sets of 14C-ages is compared with the U/Th-dated Chinese Hulu Cave speleothem records, which shows global paleoclimate change in high temporal resolution. By this synchronization we have established an absolute-dated Greenland-Hulu chronological framework, against which global paleoclimate data can be referenced, extending the 14C-age calibration curve back to the limits of the radiocarbon method. Based on this new, U/Th-based Greenland(Hulu) chronology, we confirm that the radiocarbon timescale underestimates calendar ages by several thousand years during most of Oxygen Isotope Stage 3. Major atmospheric 14C variations are observed for the period of the Middle to Upper Paleolithic transition, which has significant implications for dating the demise of the last Neandertals. The early part of "the transition" (with 14C ages > 35.0 ka 14C BP) coincides with the Laschamp geomagnetic excursion. This period is characterized by highly-elevated atmospheric 14C levels. The following period ca. 35.0-32.5 ka 14C BP shows a series of distinct large-scale 14C age inversions and extended plateaus. In consequence, individual archaeological 14C dates older than 35.0 ka 14C BP can be age-calibrated with relatively high precision, while individual dates in the interval 35.0-32.5 ka 14C BP are subject to large systematic age-'distortions,' and chronologies based on large data sets will show apparent age-overlaps of up to ca. 5,000 cal years. Nevertheless, the observed variations in past 14C levels are not as extreme as previously proposed ("Middle to Upper Paleolithic dating anomaly"), and the new chronological framework leaves ample room for application of radiocarbon dating in the age-range 45.0-25.0 ka 14C BP at high temporal resolution.
Climate warming by ca. 0.8 degree C between the late-19th and late-20th century, although with some fluctuations, has forced multispecies elevational tree-limit advance by > 100 m for the principal tree species in the Swedish part of the Scandinavian mountain range. Predominantly, these processes imply growth in height of old-established individuals and less frequently upslope migration of new individuals. After a slight retardation during some cooler decades after 1940, a new active phase of tree-limit advance has occurred with a series of exceptionally mild winters and some warm summers during the 1990s. The magnitude of total 20th century tree-limit rise varies with topoclimate and is mainly confined to wind-sheltered and snow-rich segments of the landscape. Thickening of birch tree stands in the "advance belt" has profoundly altered the general character of the subalpine/low alpine landscape and provides a positive feedback loop for further progressive change and resilience to short-term cooling episodes. All upslope tree-limit shifts and associated landscape transformations during the 20th century have occurred without appreciable time lags, which constitutes knowledge fundamental to the generation of realistic models concerning vegetation responses to potential future warming. The new and elevated pine tree-limit may be the highest during the past 4000 14C years. Thus, it is tentatively inferred that the 20th century climate is unusually warm in a late-Holocene perspective.
AIM: To specify a 24-h profile of arterial pressure (AP) in hypertensive patients working in duty regime in the Far North (Tyumen Region). MATERIAL AND METHODS: AP parameters were studied in 155 males aged 25-59 with hypertension of stage I, II who were employed for duty work in the Far North areas and 38 control patients with hypertension stage I, II living in a moderate climatic zone (Tyumen). The groups were comparable by gender, age, duration of hypertension, office systolic and diastolic AP (SAP and DAP). All the patients have undergone 24-h monitoring of AP with assessment of basic mean parameters. RESULTS: The study group patients had scare symptoms and lower mean 24-h SAP, but high AP variability, high DAD as reflection of more significant structural changes of vessels and special functioning of the autonomic nervous system in the North. Mean 24-h AP showed more unfavourable changes in hypertensive subjects who had flight from Yamburg-Moscow-Yamburg. CONCLUSION: The data of the study dictate the necessity to develop a differentiated risk strategy for health promotion, prevention and treatment of hypertension in those who work in the North of Tyumen Region in duty regime.
To understand better the link between atmospheric CO2 concentrations and climate over geological time, records of past CO2 are reconstructed from geochemical proxies. Although these records have provided us with a broad picture of CO2 variation throughout the Phanerozoic eon (the past 544 Myr), inconsistencies and gaps remain that still need to be resolved. Here I present a continuous 300-Myr record of stomatal abundance from fossil leaves of four genera of plants that are closely related to the present-day Ginkgo tree. Using the known relationship between leaf stomatal abundance and growing season CO2 concentrations, I reconstruct past atmospheric CO2 concentrations. For the past 300 Myr, only two intervals of low CO2 (2,000 p.p.m.v.) concentrations. These results are consistent with some reconstructions of past CO2 (refs 1, 2) and palaeotemperature records, but suggest that CO2 reconstructions based on carbon isotope proxies may be compromised by episodic outbursts of isotopically light methane. These results support the role of water vapour, methane and CO2 in greenhouse climate warming over the past 300 Myr.
Comment In: Nature. 2001 May 17;411(6835):247-811357108