Atlantic Deep-water Response to the Early Pliocene Shoaling of the Central American Seaway

The early Pliocene shoaling of the Central American Seaway (CAS), ~4.7–4.2 million years ago (mega annum-Ma), is thought to have strengthened Atlantic Meridional Overturning Circulation (AMOC). The associated increase in northward flux of heat and moisture may have significantly influenced the evolution of Pliocene climate. While some evidence for the predicted increase in North Atlantic Deep Water (NADW) formation exists in the Caribbean and Western Atlantic, similar evidence is missing in the wider Atlantic. Here, we present stable carbon (δ13C) and oxygen (δ18O) isotope records from the Southeast Atlantic-a key region for monitoring the southern extent of NADW. Using these data, together with other δ13C and δ18O records from the Atlantic, we assess the impact of the early Pliocene CAS shoaling phase on deep-water circulation. We find that NADW formation was vigorous prior to 4.7 Ma and showed limited subsequent change. Hence, the overall structure of the deep Atlantic was largely unaffected by the early Pliocene CAS shoaling, corroborating other evidence that indicates larger changes in NADW resulted from earlier and deeper shoaling phases. This finding implies that the early Pliocene shoaling of the CAS had no profound impact on the evolution of climate

Physicians' Reports of Focused Expertise in Clinical Practice

Little is known about the prevalence of focused expertise (special areas of expertise within a clinical field) among physicians, yet such expertise may influence how care is delivered. We surveyed general internists, pediatricians, cardiologists, infectious disease specialists, and orthopedic surgeons to describe the prevalence of focused expertise and identify associated physician and practice characteristics. About one quarter of generalists and three quarters of specialists reported a focused expertise within their primary specialty. Hospital-based physicians more often reported such expertise, and physicians reimbursed by capitation less often reported expertise. Learning how focused expertise affects processes and outcomes of care will contribute to decisions about physician training and staffing of medical groups