Nonlinear threshold behavior during the loss of Arctic sea ice

In light of the rapid recent retreat of Arctic sea ice, a number of studies have discussed the possibility of a critical threshold (or “tipping point”) beyond which the ice–albedo feedback causes the ice cover to melt away in an irreversible process. The focus has typically been centered on the annual minimum (September) ice cover, which is often seen as particularly susceptible to destabilization by the ice–albedo feedback. Here, we examine the central physical processes associated with the transition from ice-covered to ice-free Arctic Ocean conditions. We show that although the ice–albedo feedback promotes the existence of multiple ice-cover states, the stabilizing thermodynamic effects of sea ice mitigate this when the Arctic Ocean is ice covered during a sufficiently large fraction of the year. These results suggest that critical threshold behavior is unlikely during the approach from current perennial sea-ice conditions to seasonally ice-free conditions. In a further warmed climate, however, we find that a critical threshold associated with the sudden loss of the remaining wintertime-only sea ice cover may be likely

A Study in the Use of Elastic Materials in Expandable Containment Units

The rigidity of materials in conjunction with the aspect of elasticity has been a concern of modern technologies and construction in recent centuries because of the advantages that expandable storage would bring to the fields of containment units with respect to population growth and space exploration. The world population is currently growing at an exponential rate, and as our population grows, the more important it will become to have containment units that can both contain large volumes of material as well as minuscule amounts of material without wasting space. In order accomplish this, we will need a new type of storage container that utilizes the inherent strengths of both flexibility and rigidity to find a unique balance between the two. The purpose of this study is not to necessarily find the final answer to the question of expandable storage, but to narrow the range of questions that later research will use to finally answer the question, “How will we do it?” In order to research the utility of elastic material in creating storage devices in the same manner as has have described, this study would create an expandable backpack as a scaled-down case study. The backpack utilizes grooved panels made of lightweight, rigid material such as PVC-plastic in conjunction with elastic cloth, made of a mix of nylon and spandex, to create a container that will stand rigid on its own, but also expand in horizontal directions so that it can hold objects larger than its original volume. By creating male and female connectors in the individual panels, the container will be able to stand rigid, but also expand using elastic cloth sandwiched between the halves of each panel. The front and back of the container will be made of two panels, but the sides will be made up of 4 panels, so that expansion is more likely to occur in those directions, as well as lessen the stress on the fabric. In order to create the container, the team sampled multiple ratios of nylon-to-spandex, as well as tested the rigidity of different woods and plastics. Upon deciding on a material, PVC, a prototype was built and tested. The testing process involved filling the container to with varying amounts of weight, such as textbooks and laptops, and having a test subject walk around carrying the objects for varying amounts of time. The study also tested the amount of volume the backpack is able to expand, aiming for between five and ten percent increased volume. While the purpose of this study is not to solve the problem of expandable storage definitively, the concept of elastic cloth between interlocking panels has a high likelihood of being a step in the right direction

Penis size: Survey of female perceptions of sexual satisfaction

BACKGROUND: Does the size of the male penis, in terms of length or width, make a difference in female sexual satisfaction? METHOD: To study the effect of penis width vs. length on female sexual satisfaction, 50 sexually active female undergraduate students were asked which felt better, i. e., was penis width or length more important for their sexual satisfaction. RESULTS: None reported they did not know, or that width and length were equally satisfying. A large majority, 45 of 50, reported width was more important (p < .001). CONCLUSION: Implications are discussed, including the fact that the data seem to contradict Masters and Johnson about penis size having no physiological effect on female sexual satisfaction

Does wealth predict health among dogs in a protected area?

As the world's most ubiquitous carnivore, domestic dogs maintain unique proximity to human populations. Partly because dogs potentially serve as hosts of zoonotic diseases, determinants of canine health are increasingly the focus of interdisciplinary research. Emerging perspectives suggest that dogs' health may vary as a function of their owners' wealth and financial resources, a correlation that could potentially inform public health programs and conservation efforts. The objective of this study was to evaluate associations between household wealth and the health of domestic dogs (n = 208) among indigenous Mayangna communities in the Bosawás Biosphere Reserve, Nicaragua. The dogs were evaluated using serum biochemistry, complete blood count, and physical exam findings. Using these data, a principal components analysis (PCA) determined the presence of four "syndromes": 1) decreased body condition score (BCS) & hypoalbuminemia; 2) lymphocytosis & eosinophilia; 3) segmented neutrophilia; and 4) lymphadenopathy, tick infestation, & hyperglobulinemia. An inventory of possessions indexed household wealth. For all four syndromes, household wealth was a weak and uninformative predictor of the dogs' health. The few differences seen among dogs from households with different degrees of wealth likely reflect that nearly all dogs had marginal health and all households were relatively poor. Results from this study imply that owners' wealth may have diverse effects on canine health in rural settings

Decadal to seasonal variability of Arctic sea ice albedo

A controlling factor in the seasonal and climatological evolution of the sea ice cover is its albedo $\alpha$. Here we analyze Arctic data from the Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder and assess the seasonality and variability of broadband albedo from a 23 year daily record. We produce a histogram of daily albedo over ice covered regions in which the principal albedo transitions are seen; high albedo in late winter and spring, the onset of snow melt and melt pond formation in the summer, and fall freeze up. The bimodal late summer distribution demonstrates the combination of the poleward progression of the onset of melt with the coexistence of perennial bare ice with melt ponds and open water, which then merge to a broad peak at $\alpha \gtrsim$ 0.5. We find the interannual variability to be dominated by the low end of the $\alpha$ distribution, highlighting the controlling influence of the ice thickness distribution and large-scale ice edge dynamics. The statistics obtained provide a simple framework for model studies of albedo parameterizations and sensitivities.Comment: 4 pages, 4 figure

On the existence of stable seasonally varying Arctic sea ice in simple models

Within the framework of lower order thermodynamic theories for the climatic evolution of Arctic sea ice we isolate the conditions required for the existence of stable seasonally-varying solutions, in which ice forms each winter and melts away each summer. This is done by constructing a two-season model from the continuously evolving theory of Eisenman and Wettlaufer (2009) and showing that seasonally-varying states are unstable under constant annual average short-wave radiative forcing. However, dividing the summer season into two intervals (ice covered and ice free) provides sufficient freedom to stabilize seasonal ice. Simple perturbation theory shows that the condition for stability is determined by when the ice vanishes in summer and hence the relative magnitudes of the summer heat flux over the ocean versus over the ice. This scenario is examined within the context of greenhouse gas warming, as a function of which stability conditions are discerned.Comment: 11 pages, 6 figures, 1 tabl

A Spurious Jump in the Satellite Record: Has Antarctic Sea Ice Expansion Been Overestimated?

Recent estimates indicate that the Antarctic sea ice cover is expanding at a statistically significant rate with a magnitude one-third as large as the rapid rate of sea ice retreat in the Arctic. However, during the mid-2000s, with several fewer years in the observational record, the trend in Antarctic sea ice extent was reported to be considerably smaller and statistically indistinguishable from zero. Here, we show that much of the increase in the reported trend occurred due to the previously undocumented effect of a change in the way the satellite sea ice observations are processed for the widely used Bootstrap algorithm data set, rather than a physical increase in the rate of ice advance. Specifically, we find that a change in the intercalibration across a 1991 sensor transition when the data set was reprocessed in 2007 caused a substantial change in the long-term trend. Although our analysis does not definitively identify whether this change introduced an error or removed one, the resulting difference in the trends suggests that a substantial error exists in either the current data set or the version that was used prior to the mid- 2000s, and numerous studies that have relied on these observations should be reexamined to determine the sensitivity of their results to this change in the data set. Furthermore, a number of recent studies have investigated physical mechanisms for the observed expansion of the Antarctic sea ice cover. The results of this analysis raise the possibility that much of this expansion may be a spurious artifact of an error in the processing of the satellite observations

Constraining the date of a seasonally ice-free Arctic using a simple model

State-of-the-art climate models simulate a large spread in the projected decline of Arctic sea-ice area (SIA) over the 21st century. Here we diagnose causes of this intermodel spread using a model that approximates future SIA based on present SIA and the sensitivity of SIA to Arctic temperatures. This model accounts for 70-95% of the intermodel variance, with the majority of the spread arising from present-day biases. The remaining spread arises from model differences in Arctic warming, with some contribution from the local sea-ice sensitivity. Using observations to constrain the projections moves the probability of an ice-free Arctic forward by 10-35 years. Under a high-emissions scenario, an ice-free Arctic will likely (66% probability) occur in September around 2046 and from July-October around 2059. Under a medium-emissions scenario, this date occurs around 2051 in September and 2080 from July-October. These observation-based constraints imply ice-free Arctic summers are approaching faster than previously thought