Ice front blocking of ocean heat transport to an Antarctic ice shelf.

Mass loss from the Antarctic Ice Sheet to the ocean has increased in recent decades, largely because the thinning of its floating ice shelves has allowed the outflow of grounded ice to accelerate1,2. Enhanced basal melting of the ice shelves is thought to be the ultimate driver of change2,3, motivating a recent focus on the processes that control ocean heat transport onto and across the seabed of the Antarctic continental shelf towards the ice4-6. However, the shoreward heat flux typically far exceeds that required to match observed melt rates2,7,8, suggesting that other critical controls exist. Here we show that the depth-independent (barotropic) component of the heat flow towards an ice shelf is blocked by the marked step shape of the ice front, and that only the depth-varying (baroclinic) component, which is typically much smaller, can enter the sub-ice cavity. Our results arise from direct observations of the Getz Ice Shelf system and laboratory experiments on a rotating platform. A similar blocking of the barotropic component may occur in other areas with comparable ice-bathymetry configurations, which may explain why changes in the density structure of the water column have been found to be a better indicator of basal melt rate variability than the heat transported onto the continental shelf9. Representing the step topography of the ice front accurately in models is thus important for simulating ocean heat fluxes and induced melt rates.

Southern ocean carbon and heat impact on climate.

The Southern Ocean greatly contributes to the regulation of the global climate by controlling important heat and carbon exchanges between the atmosphere and the ocean. Rates of climate change on decadal timescales are therefore impacted by oceanic processes taking place in the Southern Ocean, yet too little is known about these processes. Limitations come both from the lack of observations in this extreme environment and its inherent sensitivity to intermittent processes at scales that are not well captured in current Earth system models. The Southern Ocean Carbon and Heat Impact on Climate programme was launched to address this knowledge gap, with the overall objective to understand and quantify variability of heat and carbon budgets in the Southern Ocean through an investigation of the key physical processes controlling exchanges between the atmosphere, ocean and sea ice using a combination of observational and modelling approaches. Here, we provide a brief overview of the programme, as well as a summary of some of the scientific progress achieved during its first half. Advances range from new evidence of the importance of specific processes in Southern Ocean ventilation rate (e.g. storm-induced turbulence, sea-ice meltwater fronts, wind-induced gyre circulation, dense shelf water formation and abyssal mixing) to refined descriptions of the physical changes currently ongoing in the Southern Ocean and of their link with global climate. This article is part of a discussion meeting issue 'Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities'.

Atmospheric dynamics drive most interannual U.S. droughts over the last millennium.

The American West exemplifies drought-sensitive regions with growing populations. Paleoclimate investigations have documented severe droughts in this region before European settling, with major implications for water management and planning. Here, we leverage paleoclimate data assimilation to reconstruct past climate states, enabling a large-scale multivariate investigation of U.S. drought dynamics over the last millennium. These results confirm that La Niña conditions significantly influence southwest U.S. drought over the past millennium but only account for, by one metric, ~13% of interannual drought variability in that region. Atlantic sea surface temperatures may also contribute a small influence, but unexplained variability suggests a substantial role for internal atmospheric variability. This conclusion is buttressed by analysis of simulations from the Community Earth System Model Last Millennium Ensemble. While greenhouse gases will increase future drought risk, as shown in other work, interannual U.S. drought variations will also be widely influenced by processes internal to the atmosphere.

Advanced Lemierre syndrome requiring surgery.

A 38-year-old homeless man was admitted with a 2-week history of a sore throat, increasing shortness of breath, and high fever. Clinical examination showed enlarged and tender submandibular and anterior cervical lymph nodes and a pronounced enlargement of the left peritonsillar region (Figure 1a). CT scan of the throat and the chest showed left peritonsillar abscess formation, occlusion of the left internal jugular vein with inflammatory wall thickening and perijugular soft tissue infiltration, pulmonary abscesses, and bilateral pleural effusions (Figures 1b-e, arrowed). Anaerobe blood cultures grew Fusobacterium necrophorum, leading to the diagnosis of Lemierre's syndrome. Treatment with high-dose amoxicillin and clavulanic acid improved the oropharyngeal condition, but the patient's general status declined further, marked by dyspnea and tachypnea. Repeated CT scans showed progressive lung abscesses and bilateral pleural empyema. Bilateral tonsillectomy, ligation of the left internal jugular vein, and staged decortication of bilateral empyema were performed. Total antibiotic therapy duration was 9 weeks, including a change to peroral clindamycin. Clinical and laboratory findings had returned to normal 12 weeks after surgery.The patient's history and the clinical and radiological findings are characteristic for Lemierre's syndrome. CT scans of the neck and the chest are the diagnostic methods of choice. F. necrophorum is found in over 80% of cases of Lemierre's syndrome and confirms the diagnosis. Prolonged antibiotic therapy is usually sufficient, but in selected patients, a surgical intervention may be necessary. Reported mortality rates are high, but in surviving patients, the recovery of pulmonary function is usually good.

Budget development and implementation for the APN in independent practice.

Advanced practice nurses have a unique opportunity to meet the health needs in our communities. Although laden with barriers and challenges, independent practice is a viable option for advanced practice nurses. This article reviews the critical steps to developing and implementing a budget and operational plan for a successful independent nursing practice.