Sea ice contribution to the air–sea CO₂ exchange in the Arctic and Southern Oceans

Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO2 and the subsequent effect on air–sea CO2 exchange have received little attention. We review the mechanisms by which sea ice directly and indirectly controls the air–sea CO2 exchange and use recent measurements of inorganic carbon compounds in bulk sea ice to estimate that oceanic CO2 uptake during the seasonal cycle of sea-ice growth and decay in ice-covered oceanic regions equals almost half of the net atmospheric CO2 uptake in ice-free polar seas. This sea-ice driven CO2 uptake has not been considered so far in estimates of global oceanic CO2 uptake. Net CO2 uptake in sea-ice–covered oceans can be driven by; (1) rejection during sea–ice formation and sinking of CO2-rich brine into intermediate and abyssal oceanic water masses, (2) blocking of air–sea CO2 exchange during winter, and (3) release of CO2-depleted melt water with excess total alkalinity during sea-ice decay and (4) biological CO2 drawdown during primary production in sea ice and surface oceanic waters

Photoionisation loading of large Sr+ ion clouds with ultrafast pulses

This paper reports on photoionisation loading based on ultrafast pulses of singly-ionised strontium ions in a linear Paul trap. We take advantage of an autoionising resonance of Sr neutral atoms to form Sr+ by two-photon absorption of femtosecond pulses at a wavelength of 431nm. We compare this technique to electron-bombardment ionisation and observe several advantages of photoionisation. It actually allows the loading of a pure Sr+ ion cloud in a low radio-frequency voltage amplitude regime. In these conditions up to 4x10^4 laser-cooled Sr+ ions were trapped

Rising rural body-mass index is the main driver of the global obesity epidemic in adults

Body-mass index (BMI) has increased steadily in most countries in parallel with a rise in the proportion of the population who live in cities 1,2 . This has led to a widely reported view that urbanization is one of the most important drivers of the global rise in obesity 3�6 . Here we use 2,009 population-based studies, with measurements of height and weight in more than 112 million adults, to report national, regional and global trends in mean BMI segregated by place of residence (a rural or urban area) from 1985 to 2017. We show that, contrary to the dominant paradigm, more than 55 of the global rise in mean BMI from 1985 to 2017�and more than 80 in some low- and middle-income regions�was due to increases in BMI in rural areas. This large contribution stems from the fact that, with the exception of women in sub-Saharan Africa, BMI is increasing at the same rate or faster in rural areas than in cities in low- and middle-income regions. These trends have in turn resulted in a closing�and in some countries reversal�of the gap in BMI between urban and rural areas in low- and middle-income countries, especially for women. In high-income and industrialized countries, we noted a persistently higher rural BMI, especially for women. There is an urgent need for an integrated approach to rural nutrition that enhances financial and physical access to healthy foods, to avoid replacing the rural undernutrition disadvantage in poor countries with a more general malnutrition disadvantage that entails excessive consumption of low-quality calories. © 2019, The Author(s)