Observational evidence for on-shelf heat transport driven by dense water export in the Weddell Sea.

The transport of oceanic heat towards the Antarctic continental margin is central to the mass balance of the Antarctic Ice Sheet. Recent modeling efforts challenge our view on where and how the on-shelf heat flux occurs, suggesting that it is largest where dense shelf waters cascade down the continental slope. Here we provide observational evidence supporting this claim. Using records from moored instruments, we link the downslope flow of dense water from the Filchner overflow to upslope and on-shelf flow of warm water.

Suppressed basal melting in the eastern Thwaites Glacier grounding zone.

Thwaites Glacier is one of the fastest-changing ice-ocean systems in Antarctica1-3. Much of the ice sheet within the catchment of Thwaites Glacier is grounded below sea level on bedrock that deepens inland4, making it susceptible to rapid and irreversible ice loss that could raise the global sea level by more than half a metre2,3,5. The rate and extent of ice loss, and whether it proceeds irreversibly, are set by the ocean conditions and basal melting within the grounding-zone region where Thwaites Glacier first goes afloat3,6, both of which are largely unknown. Here we show-using observations from a hot-water-drilled access hole-that the grounding zone of Thwaites Eastern Ice Shelf (TEIS) is characterized by a warm and highly stable water column with temperatures substantially higher than the in situ freezing point. Despite these warm conditions, low current speeds and strong density stratification in the ice-ocean boundary layer actively restrict the vertical mixing of heat towards the ice base7,8, resulting in strongly suppressed basal melting. Our results demonstrate that the canonical model of ice-shelf basal melting used to generate sea-level projections cannot reproduce observed melt rates beneath this critically important glacier, and that rapid and possibly unstable grounding-line retreat may be associated with relatively modest basal melt rates.

Rapid basal melting of the Greenland Ice Sheet from surface meltwater drainage.

Subglacial hydrologic systems regulate ice sheet flow, causing acceleration or deceleration, depending on hydraulic efficiency and the rate at which surface meltwater is delivered to the bed. Because these systems are rarely observed, ice sheet basal drainage represents a poorly integrated and uncertain component of models used to predict sea level changes. Here, we report radar-derived basal melt rates and unexpectedly warm subglacial conditions beneath a large Greenlandic outlet glacier. The basal melt rates averaged 14 mm ⋅d-1 over 4 months, peaking at 57 mm ⋅d-1 when basal water temperature reached +0.88 ∘C in a nearby borehole. We attribute both observations to the conversion of potential energy of surface water to heat in the basal drainage system, which peaked during a period of rainfall and intense surface melting. Our findings reveal limitations in the theory of channel formation, and we show that viscous dissipation far surpasses other basal heat sources, even in a distributed, high-pressure system.

Observed interannual changes beneath Filchner-Ronne Ice Shelf linked to large-scale atmospheric circulation.

Floating ice shelves are the Achilles' heel of the Antarctic Ice Sheet. They limit Antarctica's contribution to global sea level rise, yet they can be rapidly melted from beneath by a warming ocean. At Filchner-Ronne Ice Shelf, a decline in sea ice formation may increase basal melt rates and accelerate marine ice sheet mass loss within this century. However, the understanding of this tipping-point behavior largely relies on numerical models. Our new multi-annual observations from five hot-water drilled boreholes through Filchner-Ronne Ice Shelf show that since 2015 there has been an intensification of the density-driven ice shelf cavity-wide circulation in response to reinforced wind-driven sea ice formation in the Ronne polynya. Enhanced southerly winds over Ronne Ice Shelf coincide with westward displacements of the Amundsen Sea Low position, connecting the cavity circulation with changes in large-scale atmospheric circulation patterns as a new aspect of the atmosphere-ocean-ice shelf system.

Tidal Modulation of Buoyant Flow and Basal Melt Beneath Petermann Gletscher Ice Shelf, Greenland.

A set of collocated, in situ oceanographic and glaciological measurements from Petermann Gletscher Ice Shelf, Greenland, provides insights into the dynamics of under-ice flow driving basal melting. At a site 16 km seaward of the grounding line within a longitudinal basal channel, two conductivity-temperature (CT) sensors beneath the ice base and a phase-sensitive radar on the ice surface were used to monitor the coupled ice shelf-ocean system. A 6 month time series spanning 23 August 2015 to 12 February 2016 exhibited two distinct periods of ice-ocean interactions. Between August and December, radar-derived basal melt rates featured fortnightly peaks of ∼15 m yr-1 which preceded the arrival of cold and fresh pulses in the ocean that had high concentrations of subglacial runoff and glacial meltwater. Estimated current speeds reached 0.20 - 0.40 m s-1 during these pulses, consistent with a strengthened meltwater plume from freshwater enrichment. Such signals did not occur between December and February, when ice-ocean interactions instead varied at principal diurnal and semidiurnal tidal frequencies, and lower melt rates and current speeds prevailed. A combination of estimated current speeds and meltwater concentrations from the two CT sensors yields estimates of subglacial runoff and glacial meltwater volume fluxes that vary between 10 and 80 m3 s-1 during the ocean pulses. Area-average upstream ice shelf melt rates from these fluxes are up to 170 m yr-1, revealing that these strengthened plumes had already driven their most intense melting before arriving at the study site.

Strong ice-ocean interaction beneath Shirase Glacier Tongue in East Antarctica.

Mass loss from the Antarctic ice sheet, Earth's largest freshwater reservoir, results directly in global sea-level rise and Southern Ocean freshening. Observational and modeling studies have demonstrated that ice shelf basal melting, resulting from the inflow of warm water onto the Antarctic continental shelf, plays a key role in the ice sheet's mass balance. In recent decades, warm ocean-cryosphere interaction in the Amundsen and Bellingshausen seas has received a great deal of attention. However, except for Totten Ice Shelf, East Antarctic ice shelves typically have cold ice cavities with low basal melt rates. Here we present direct observational evidence of high basal melt rates (7-16 m yr-1) beneath an East Antarctic ice shelf, Shirase Glacier Tongue, driven by southward-flowing warm water guided by a deep continuous trough extending to the continental slope. The strength of the alongshore wind controls the thickness of the inflowing warm water layer and the rate of basal melting.

The Southern Ocean and its interaction with the Antarctic Ice Sheet.

The Southern Ocean exerts a major influence on the mass balance of the Antarctic Ice Sheet, either indirectly, by its influence on air temperatures and winds, or directly, mostly through its effects on ice shelves. How much melting the ocean causes depends on the temperature of the water, which in turn is controlled by the combination of the thermal structure of the surrounding ocean and local ocean circulation, which in turn is determined largely by winds and bathymetry. As climate warms and atmospheric circulation changes, there will be follow-on changes in the ocean circulation and temperature. These consequences will affect the pace of mass loss of the Antarctic Ice Sheet.

Summer surface melt thins Petermann Gletscher Ice Shelf by enhancing channelized basal melt.

Increasing ocean and air temperatures have contributed to the removal of floating ice shelves from several Greenland outlet glaciers; however, the specific contribution of these external forcings remains poorly understood. Here we use atmospheric, oceanographic, and glaciological time series data from the ice shelf of Petermann Gletscher, NW Greenland to quantify the forcing of the ocean and atmosphere on the ice shelf at a site ~16 km from the grounding line within a large sub-ice-shelf channel. Basal melt rates here indicate a strong seasonality, rising from a winter mean of 2 m yr-1 to a maximum of 80 m yr-1 during the summer melt season. This increase in basal melt rates confirms the direct link between summer atmospheric warming around Greenland and enhanced ocean-forced melting of its remaining ice shelves. We attribute this enhanced melting to increased discharge of subglacial runoff into the ocean at the grounding line, which strengthens under-ice currents and drives a greater ocean heat flux toward the ice base.

Rapid mixing and exchange of deep-ocean waters in an abyssal boundary current.

The overturning circulation of the global ocean is critically shaped by deep-ocean mixing, which transforms cold waters sinking at high latitudes into warmer, shallower waters. The effectiveness of mixing in driving this transformation is jointly set by two factors: the intensity of turbulence near topography and the rate at which well-mixed boundary waters are exchanged with the stratified ocean interior. Here, we use innovative observations of a major branch of the overturning circulation-an abyssal boundary current in the Southern Ocean-to identify a previously undocumented mixing mechanism, by which deep-ocean waters are efficiently laundered through intensified near-boundary turbulence and boundary-interior exchange. The linchpin of the mechanism is the generation of submesoscale dynamical instabilities by the flow of deep-ocean waters along a steep topographic boundary. As the conditions conducive to this mode of mixing are common to many abyssal boundary currents, our findings highlight an imperative for its representation in models of oceanic overturning.

Training Community Health Workers to Enhance Disaster Resilience.

Community health workers (CHWs) have significant potential to contribute to public health in the United States by promoting disaster preparedness, speeding postdisaster recovery, and building disaster resilience in their communities. To maximize this potential, however, they must undergo rigorous and relevant training. As part of the Gulf Region Health Outreach Program, an appropriate curriculum was developed and delivered in several training sessions conducted from 2013 to 2016. This article provides insights into the primary issues associated with such training and offers a detailed elaboration of the basic and specialized curricula as presented and adapted over the course of the program. We present lessons learned from these training experiences, as reflected in participants' initial ratings and comments, training staff debriefings, and feedback from CHWs working in the field. Informed by this feedback, as well as additional research and conceptual development, we offer recommendations aimed at expanding and refining CHW training curricula in the areas of chronic disease, psychosocial symptoms, community resilience, and environmental health. In addition to curriculum changes, we review policy implications aimed at promoting and facilitating the inclusion of CHWs in disaster response and recovery teams.

Bimodal Winter Haul-Out Patterns of Adult Weddell Seals (Leptonychotes weddellii) in the Southern Weddell Sea.

Hauling out is an essential component of pinniped life-history. Haul-out behaviour may be affected by biological (e.g. sex, age and condition) and physical factors (e.g. food availability and environmental conditions), and identifying these factors may help explain the spatio-temporal distribution and habitat use of pinnipeds. The aim of this study is to describe observed winter haul-out patterns of adult Weddell seals in the Weddell Sea and investigate the role of potential predictors to gain insight into the way these animals interact with the physical environment in this region. We examined the haul-out behaviour in relation to available biological (i.e., diving effort, sex) and physical information (i.e., sun angle). Thirty-three satellite telemetry tags were deployed on adult Weddell seals in the southern Weddell Sea during February 2007, 2009 and 2011, following their annual moult recording information on the behavioural mode of the animal: at surface, hauled out or diving. At the end of the austral summer Weddell seals spent, on average, more than 40% of their time hauled out on the ice. Under constant light conditions, it appears that physiological factors drive sex differences in the timing and duration of haul-out behaviour, with females spending on average more time hauled out than males during daylight hours. This time spent hauled-out declined to around 15% in both sexes by the beginning of autumn and remained at this level with a clear nocturnal haul-out pattern during the winter. The time spent diving increased during this period, indicating an increase in foraging effort during the winter months, and led to a common haul-out pattern in both sexes over winter. We found a positive relationship between haul-out duration and the percentage of time spent diving prior to a haul-out in both sexes, with the exception of female daytime haul-outs early in the year.

Differences in Colorectal Cancer Risk Knowledge Among Alabamians: Screening Implications.

PURPOSE/OBJECTIVES: To explore differences in cancer risk knowledge and colorectal cancer (CRC) knowledge among adults in Alabama. 
. RESEARCH APPROACH: Telephone interviews were conducted using an 80-item questionnaire that included 14 demographic questions and 26 general questions regarding healthcare quality, sources of health-related information, and cancer fears and risk factors. Also included were 40 questions dealing with CRC perceptions and experiences (asked only of respondents aged 50 years or older).
. SETTING: A standard random-digit-dialed statewide telephone survey, targeting adult residents of Alabama. Interviews were conducted during about seven weeks in 2012. 
. PARTICIPANTS: 1,024 participants, including 615 who were aged 50 years or older. Most of the participants identified as Caucasian.
. METHODOLOGIC APPROACH: A secondary data analysis using data from a CRC screening survey of Alabama residents conducted in 2012 by the University of South Alabama polling group via telephone.
. FINDINGS: Knowledge of general cancer risk factors predicted disagreement with the statement, "There is nothing you can do to avoid getting cancer," and disagreement with the statement, "Only people with signs or symptoms should be screened for CRC." Binary logistic regression showed that those higher in CRC risk knowledge were more likely to have been screened for CRC. 
. CONCLUSIONS: Knowledge of general cancer risk factors may increase self-efficacy. In addition, individuals with increased knowledge of colorectal cancer risk factors were more likely to participate in CRC screening. 
. INTERPRETATION: Nurses play an instrumental role in addressing CRC, a preventable and treatable cancer. An opportunity exists for nurses and other healthcare providers to develop culturally appropriate educational interventions to increase knowledge related to CRC, risk factors, and screening, particularly among those who are at increased risk. This education needs to occur in clinical practice and within the community.

An Intensive Observation of Calving at Helheim Glacier, East Greenland.

Calving of glacial ice into the ocean from the Greenland Ice Sheet is an important component of global sea level rise. The calving process itself is relatively poorly observed, understood, and modeled; as such, it represents a bottleneck in improving future global sea level estimates in climate models. We organized a pilot project to observe the calving process at Helheim Glacier in East Greenland in an effort to better understand it. During an intensive one-week survey, we deployed a suite of instrumentation including a terrestrial radar interferometer, GPS receivers, seismometers, tsunameters, and an automated weather station. This effort captured a calving process and measured various glaciological, oceanographic, and atmospheric parameters before, during, and after the event. One outcome of our observations is evidence that the calving process actually consists of a number of discrete events, spread out over time, in this instance over at least two days. This time span has implications for models of the process. Realistic projections of future global sea level will depend on accurate parametrization of calving, which will require more sustained observations.

Attitudes toward colorectal cancer screening in the digital age: a survey of practices and attitudes among screening-eligible Alabamians.

OBJECTIVES: To ascertain barriers to colorectal cancer screening in an environment of changing recommendations, payment structures, and information access, and to develop strategies for overcoming these barriers by undertaking a population survey of colorectal cancer (CRC) screening knowledge and attitudes in Alabama. METHODS: An 80-item questionnaire focused on cancer screening, specifically CRC screening, was developed and pretested. A random sample of Alabama residents was generated using random-digit dial methods and interviews of 615 participants aged 50 and older were conducted in March 2012 and April 2012. Screened and unscreened groups were compared using χ statistics. RESULTS: Sixty-one percent of Alabamians who participated in this survey reported being screened for CRC, the majority (95%) of these by colonoscopy. Both screened and unscreened participants reported using the Internet for health information more often if they were younger than 65 years. Those screened often reported feeling well informed regarding the guidelines, often to have discussed CRC screening with their family physician, and often to have had other cancer screenings. All of the respondents, screened and unscreened, reported financial considerations to be the most significant barriers to screening. CONCLUSIONS: Although educating the general population could be helpful, a physician championing screening is key. Home stool testing is underused in Alabama in part because physicians are not fully aware of its utility. As financial barriers diminish, it is important to offer multiple effective modalities when available, and insurance reform, which includes payment for preventive care, may improve screening rates.

Colorectal cancer screening practices in Alabama: a survey of primary care physicians.

In order to inform efforts to increase screening rates for colorectal cancer (CRC), we conducted a survey of Alabama primary care physicians regarding CRC screening practices, educational preferences, and perceptions of obstacles to screening. A mail survey of 2,378 Alabama physicians in Family Medicine, Internal Medicine, and Obstetrics & Gynecology was conducted. Many physicians are not fully up-to-date with current CRC screening practices that could improve patient compliance with screening guidelines. One example is the potential use of high-sensitivity stool tests, such as the fecal immunochemical test, instead of the no longer recommended low-sensitivity guaiac fecal occult blood tests. In addition, enhanced multimedia and web-based approaches to educating physicians and patients could be more fully utilized. Further, greater use of health information technologies could increase screening rates. Enhancing primary care physicians' knowledge of screening modalities and increasing their use of electronic technology could significantly improve colorectal cancer screening outcomes.

Enhancing response rates in physician surveys: the limited utility of electronic options.

OBJECTIVE: To evaluate the utility of offering physicians electronic options as alternatives to completing mail questionnaires. DATA SOURCE: A survey of colorectal cancer screening practices of Alabama primary care physicians, conducted May-June 2010. STUDY DESIGN: In the follow-up to a mail questionnaire, physicians were offered options of completing surveys by telephone, fax, email, or online. DATA COLLECTION METHOD: Detailed records were kept on the timing and mode of completion of surveys. PRINCIPAL FINDINGS: Eighty-eight percent of surveys were returned by mail, 10 percent were returned by fax, and only 2 percent were completed online; none were completed by telephone or email. CONCLUSIONS: Offering fax options increases response rates, but providing other electronic options does not.