Return of warm conditions in the southeastern Bering Sea: Physics to fluorescence.

From 2007 to 2013, the southeastern Bering Sea was dominated by extensive sea ice and below-average ocean temperatures. In 2014 there was a shift to reduced sea ice on the southern shelf and above-average ocean temperatures. These conditions continued in 2015 and 2016. During these three years, the spring bloom at mooring site M4 (57.9°N, 168.9°W) occurred primarily in May, which is typical of years without sea ice. At mooring site M2 (56.9°N, 164.1°W) the spring bloom occurred earlier especially in 2016. Higher chlorophyll fluorescence was observed at M4 than at M2. In addition, these three warm years continued the pattern near St. Matthew Island of high concentrations (>1 µM) of nitrite occurring during summer in warm years. Historically, the dominant parameters controlling sea-ice extent are winds and air temperature, with the persistence of frigid, northerly winds in winter and spring resulting in extensive ice. After mid-March 2014 and 2016 there were no cold northerly or northeasterly winds. Cold northerly winds persisted into mid-April in 2015, but did not result in extensive sea ice south of 58°N. The apparent mechanism that helped limit ice on the southeastern shelf was the strong advection of warm water from the Gulf of Alaska through Unimak Pass. This pattern has been uncommon, occurring in only one other year (2003) in a 37-year record of estimated transport through Unimak Pass. During years with no sea ice on the southern shelf (e.g. 2001-2005, 2014-2016), the depth-averaged temperature there was correlated to the previous summers ocean temperature.

Changes in Ocean Heat, Carbon Content, and Ventilation: A Review of the First Decade of GO-SHIP Global Repeat Hydrography.

Global ship-based programs, with highly accurate, full water column physical and biogeochemical observations repeated decadally since the 1970s, provide a crucial resource for documenting ocean change. The ocean, a central component of Earth's climate system, is taking up most of Earth's excess anthropogenic heat, with about 19% of this excess in the abyssal ocean beneath 2,000 m, dominated by Southern Ocean warming. The ocean also has taken up about 27% of anthropogenic carbon, resulting in acidification of the upper ocean. Increased stratification has resulted in a decline in oxygen and increase in nutrients in the Northern Hemisphere thermocline and an expansion of tropical oxygen minimum zones. Southern Hemisphere thermocline oxygen increased in the 2000s owing to stronger wind forcing and ventilation. The most recent decade of global hydrography has mapped dissolved organic carbon, a large, bioactive reservoir, for the first time and quantified its contribution to export production (∼20%) and deep-ocean oxygen utilization. Ship-based measurements also show that vertical diffusivity increases from a minimum in the thermocline to a maximum within the bottom 1,500 m, shifting our physical paradigm of the ocean's overturning circulation.

Molecular interactions in intermediate and transition states in the self-stimulated inhibition of enzymes.

Di-isopropyl fluorophosphate (DFP) and other organophosphorus inhibitors recruit the catalytic power of their target enzymes: the enzyme catalyzes its own irreversible phosphorylation. The magnitude of the catalytic acceleration can approach the factor by which the enzyme catalyzes its own acylation by natural substrates. The reaction of DFP with five serine proteases [chymotrypsin, elastase, dipeptidyl peptidase IV (DP IV), subtilisin and thermitase] exhibits in all cases the same pH dependence as does enzyme acylation by natural substrates. Chymotrypsin and elastase form a "fast" class of enzymes which react about ten-fold faster than the other three "slow" enzymes. All enzymes show k(HOH)/k(DOD) of about 2 but the proton inventory indicates one-proton character for "slow" enzymes and multiproton character for "fast" enzymes. Enthalpies of activation are about 33 kJ/mol (subtilisin, "slow") and 10 kJ/mol (elastase, "fast"). Entropies of activation are about -120 J.T-1.mol-1 (subtilisin, "slow") and -175J.T-1.s-1 (elastase, "fast"; T = temperature in K).