Arctic response to a warming world
Regional studies of paleoclimate provide important insights into how different parts of the Earth system respond to global climate change. Geochemical data gathered for cave deposits from northeast Greenland have now provided the first paleoclimate record for the High Arctic during an interglacial warming event extending from 588 to 549 thousand years ago. Moseley et al. show that the High Arctic at that time was at least 3.5°C warmer than today during that interval, with extensive permafrost thaw and markedly increased precipitation. Comparisons with datasets for that interval from elsewhere in the world suggest that the Arctic regions were affected more substantially during this warming event, and the same can be anticipated as anthropogenic global warming continues into the future.
Carbon cycle history
Marine carbon includes organic and inorganic components, both of which must be accounted for to understand the global carbon cycle. Paytan et al. assembled a record of stable strontium isotopes (88Sr and 86Sr) derived from pelagic marine barite and used it to reconstruct changes in the deposition and burial of biogenic calcium carbonate in marine sediments. These data, when combined with measurements of 87Sr/86Sr, can help to reveal past changes in the sources and sinks of strontium, as well as variations in carbonate deposition that affect the carbon cycle.
Cell cycle regulation
The hormone cytokinin regulates various aspects of plant development and physiology, largely by managing cell proliferation. Yang et al. show that cytokinin promotes nuclear localization of the transcription factor MYB3R4, which activates the expression of two importins and genes that tip the cell into the next phase of the cell cycle. The importins facilitate further MYB3R4 accumulation within the nucleus, accelerating the progression into mitosis. MYB3R4 and the importins dissipate when the nuclear membrane dissolves at prometaphase, so there is only one round of mitotic activation per cell cycle.