A century of observed temperature change in the Indian Ocean

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wenegrat, J. O., Bonanno, E., Rack, U., & Gebbie, G. A century of observed temperature change in the Indian Ocean. Geophysical Research Letters, 49(13), (2022): e2022GL098217, https://doi.org/10.1029/2022GL098217.The Indian Ocean is warming rapidly, with widespread effects on regional weather and global climate. Sea-surface temperature records indicate this warming trend extends back to the beginning of the 20th century, however the lack of a similarly long instrumental record of interior ocean temperatures leaves uncertainty around the subsurface trends. Here we utilize unique temperature observations from three historical German oceanographic expeditions of the late 19th and early 20th centuries: SMS Gazelle (1874–1876), Valdivia (1898–1899), and SMS Planet (1906–1907). These observations reveal a mean 20th century ocean warming that extends over the upper 750 m, and a spatial pattern of subsurface warming and cooling consistent with a 1°–2° southward shift of the southern subtropical gyre. These interior changes occurred largely over the last half of the 20th century, providing observational evidence for the acceleration of a multidecadal trend in subsurface Indian Ocean temperature.GG is supported by U.S. NSF-OCE 82280500

The great opportunity: Evolutionary applications to medicine and public health

Evolutionary biology is an essential basic science for medicine, but few doctors and medical researchers are familiar with its most relevant principles. Most medical schools have geneticists who understand evolution, but few have even one evolutionary biologist to suggest other possible applications. The canyon between evolutionary biology and medicine is wide. The question is whether they offer each other enough to make bridge building worthwhile. What benefits could be expected if evolution were brought fully to bear on the problems of medicine? How would studying medical problems advance evolutionary research? Do doctors need to learn evolution, or is it valuable mainly for researchers? What practical steps will promote the application of evolutionary biology in the areas of medicine where it offers the most? To address these questions, we review current and potential applications of evolutionary biology to medicine and public health. Some evolutionary technologies, such as population genetics, serial transfer production of live vaccines, and phylogenetic analysis, have been widely applied. Other areas, such as infectious disease and aging research, illustrate the dramatic recent progress made possible by evolutionary insights. In still other areas, such as epidemiology, psychiatry, and understanding the regulation of bodily defenses, applying evolutionary principles remains an open opportunity. In addition to the utility of specific applications, an evolutionary perspective fundamentally challenges the prevalent but fundamentally incorrect metaphor of the body as a machine designed by an engineer. Bodies are vulnerable to disease – and remarkably resilient – precisely because they are not machines built from a plan. They are, instead, bundles of compromises shaped by natural selection in small increments to maximize reproduction, not health. Understanding the body as a product of natural selection, not design, offers new research questions and a framework for making medical education more coherent. We conclude with recommendations for actions that would better connect evolutionary biology and medicine in ways that will benefit public health. It is our hope that faculty and students will send this article to their undergraduate and medical school Deans, and that this will initiate discussions about the gap, the great opportunity, and action plans to bring the full power of evolutionary biology to bear on human health problems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90555/1/j.1752-4571.2007.00006.x.pd

Ocean Boundary Layer Dynamics and Air-Sea Interaction

Thesis (Ph.D.)--University of Washington, 2005-12The dynamics of the ocean surface boundary layer are examined using theory, high-resolution moored observations from the equatorial Atlantic ocean, and idealized modeling. An approximate solution is found for the ocean response to wind-forcing in the presence of baroclinic pressure gradients, surface wave shear, and spatially varying turbulent mixing. The manner in which these parameters modify the classic physical model of the wind-forced ocean is discussed, and estimates of their spatial distribution are provided. Next, the role of time-varying shear in determining the near-surface eddy viscosity is assessed using velocity observations from the equatorial Atlantic, and the implications for several simple parameterizations are considered. These observations are then utilized to provide a first in situ observational assessment of the diurnal cycle of shear and stratification in the equatorial Atlantic, demonstrating how mixed-layer dynamics modulate the diurnal cycle of sea surface temperature, coupling the dynamic and thermodynamic responses. Further, these results suggest the existence of a deep-cycle turbulence layer in the equatorial Atlantic, providing a complementary perspective on similar recent work from the Pacific. Finally, the effect of time-varying eddy viscosity on the low-frequency wind-driven flow is assessed using theory and idealized modeling, providing a new conceptual tool for understanding the dynamics of the near-surface ocean, and for guiding the interpretation of observations. A particular focus throughout this thesis is the role of ocean dynamics in determining the near-surface ocean response to surface atmospheric fluxes

Slippery bottom boundary layers: the loss of energy from the general circulation by bottom drag

Bottom drag is believed to be one of the key mechanisms that remove kinetic energy from the ocean's general circulation. However, large uncertainty still remains in global estimates of bottom drag dissipation. One significant source of uncertainty comes from the velocity structures near the bottom where the combination of sloping topography and stratification can reduce the mean flow magnitude, and thus the bottom drag dissipation. Using high-resolution numerical simulations, we demonstrate that previous estimates of bottom drag dissipation are biased high because they neglect velocity shear in the bottom boundary layer. The estimated bottom drag dissipation associated with geostrophic flows over the continental slopes is at least 56% smaller compared with prior estimates made using total velocities outside of the near-bottom layer. The diagnostics suggest the necessity of resolving the bottom boundary layer structures in coarse-resolution ocean models and observations in order to close the global kinetic energy budget. Plain Language Summary When an oceanic flow is close to the seafloor, the bottom drag converts its kinetic energy (KE) to heat loss through viscous friction, and this dissipation of KE has been shown to be very sensitive to the magnitude of the flow. Despite previous estimates indicating the bottom drag being a significant mechanism for removing KE from the ocean's general circulation, large uncertainty still remains. Using high-resolution numerical simulations of the Atlantic Ocean, we demonstrate that accounting for the velocity reduction through the oceanic bottom boundary layer reduces kinetic energy loss from the balanced flow (in which the pressure gradient force and Coriolis force balance) by at least 56% over the continental slopes. This velocity reduction is due to the presence of sloping topography and ocean stratification near the bottom, which should be resolved in future observational and modeling efforts toward a more complete picture of the ocean's energy budget

Effects of the submesoscale on the potential vorticity budget of ocean mode waters

Non-conservative processes change the potential vorticity (PV) of the upper ocean, and later, through the subduction of surface waters into the interior, affect the general ocean circulation. Here we focus on how boundary layer turbulence, in the presence of submesoscale horizontal buoyancy gradients, generates a source of potential vorticity at the ocean surface through a balance known as the Turbulent ThermalWind. This source of PV injection at the submesoscale can be of similar magnitude to PV fluxes from the wind and surface buoyancy fluxes, and hence can lead to a net injection of PV onto outcropped isopycnals even during periods of surface buoyancy loss. The significance of these dynamics is illustrated using a high-resolution realistic model of the North Atlantic Subtropical Mode Water (18° water), where it is demonstrated that injection of PV at the submesoscale reduces the rate of mode-water PV removal by a factor of ~ 2, and shortens the annual period of mode water formation by ~3 weeks, relative to air-sea fluxes alone. Submesoscale processes thus provide a direct link between small-scale boundary layer turbulence and the gyre-scale circulation, through their effect on mode water formation, with implications for understanding the variability and biogeochemical properties of ocean mode waters globally

S-MODE: The Sub-Mesoscale Ocean Dynamics Experiment

The Sub-Mesoscale Ocean Dynamics Experiment (S-MODE) is a NASA Earth Ventures Suborbital Investigation designed to test the hypothesis that kilometer-scale (\u27submesoscale\u27) ocean eddies make important contributions to vertical exchange of climate and biological variables in the upper ocean. To test this hypothesis, S-MODE will employ a combination of aircraft-based remote sensing measurements of the ocean surface, measurements from ships, measurements from a variety of autonomous oceanographic platforms, and numerical modeling. The field campaign will consist of two month-long intensive operating periods (IOPs) that will be preceded by a smaller-scale pilot experiment to test and improve operational readiness and to compare measurements made from different platforms. The pilot experiment was delayed because of the 2020 coronavirus pandemic, and it is currently planned for October-November 2020