Wallace S. Broecker (1931 - 2019)

The correlation between modern tropical mean annual precipitation (MAP) and its isotopic composition (δp) has been extensively used to interpret terrestrial paleoclimate records. However, the existence of this phenomenon in the past and in individual regions remains a matter of debate. Here, we describe a method for evaluating the relationship between local δp and local MAP in the past (i.e. the “local amount effect”) and apply this method to a closed-basin lake in northeastern China. We measured compound specific hydrogen isotopes from plant-wax derived long-chain n-alkanes (δ2Hwax) and fatty acids (δ2HFA) from lake sediments, which primarily record local δp, and compared them with the lake level and area history of the lake, which records local MAP. Both the lake level reconstruction and the organic isotope proxies are derived from the same samples and thus enable a direct comparison. In addition, we …

In recent years, although physics has not experienced the sort of revolutions that took place during the first quarter of the twentieth century, the seeds planted at that time are still bearing fruit and continue to engender new developments. This article looks at some of them, beginning with the discovery of the Higgs boson and gravitational radiation. A deeper look reveals the additional need to address other discoveries where physics reveals its unity with astrophysics and cosmology. These include dark matter, black holes, and multiple universes. String theory and supersymmetry are also considered, as is quantum entanglement and its uses in the area of secure communications (quantum cryptography). The article concludes with a look at the presence and importance of physics in a scientifically interdisciplinary world.Physics is considered the queen of twentieth-century science, and rightly so, as that century was marked by two revolutions that drastically modified its foundations and ushered in profound socioeconomic changes: the special and general theories of relativity (Albert Einstein, 1905, 1915) and quantum physics, which, unlike relativity, cannot be attributed to a single figure as it emerged from the combined efforts of a large group of scientists. Now, we know that revolutions, whether in science, politics, or customs, have long-range effects that may not be as radical as those that led to the initial break, but can nonetheless lead to later developments, discoveries, or ways of understanding reality that were previously inconceivable. That is what happened with physics once the new basic theories were completed. In the case of quantum …

Rock varnish is a manganiferous dark coating accreted on subaerially exposed rocks in drylands. It often contains a layered microstratigraphy that records past wetness variations. Varnish samples from latest Pleistocene and Holocene geomorphic features in the Lake Turkana basin, East Africa display a regionally replicable microstratigraphy record of Holocene millennial-scale wetness variability and a broad interval of wetter conditions during the African Humid Period (AHP). Three major wet pulses in the varnish record occurred during the generally wet interval of the early Holocene (11.5–8.5 ka) when the lake attained its maximum high stand (MHS) at 455–460 m. A >23 m drop from the MHS occurred between 8.5 and 8 ka. Subsequently two additional wet pulses occurred during the early to middle Holocene (8–5 ka) when the lake occupied its secondary high stand at 445 m. Collectively, these five wet …