Seasonal Cumulative Effect of Ural Blocking Episodes on the Frequent Cold events in China during the Early Winter of 2020/21

Starting in mid-November, China was hit by several cold events during the early winter of 2020/21. The lowest temperature observed at Beijing station on 7 January reached −19.6°C. In this paper, we show that the outbreak of the record-breaking extreme cold event can be attributed to a huge merging Ural blocking (UB) ridge over the Eurasian region. The sea-ice cover in the Kara and East Siberia Seas (KESS) in autumn was at its lowest value since 1979, which could have served as a precursor signal. Further analysis shows that several successive UB episodes occurred from 1 September 2020 to 10 January 2021. The persistent UB that occurred in late September/early October 2020 may have made an important contribution to the October historical minimum of sea ice in the KESS region. Our results also show that, after each UB episode in winter, significant upward propagation of wave activity occurred around 60°E, which resulted in weakening the stratospheric vortex. Meanwhile, each UB episode also caused a significant reduction in sea-ice extent in KESS and a significant weakening of the westerly jet in mid-high-latitude Eurasia. Results suggest that the Arctic vortex, which is supposed to enhance seasonally, became weaker and more unstable than the climatic mean under the seasonal cumulative effects of UB episodes, KESS warming, and long-lasting negative-phase North Atlantic Oscillation (NAO-). Those seasonal cumulative effects, combined with the impact of La Niña winter, led to the frequent occurrence of extreme cold events.

Causes and Mechanisms of Global Warming/Climate Change

Comparison of the average mean surface air temperature around the world during 1951–1978 with that for 2010–2019 shows that the bulk of the warming is around the North Atlantic/Arctic region in contrast to the Antarctic ice sheet. Obviously, the temperature change is not global. Since there is a substantial difference between solar heat absorption between the equator and the poles, heat must be moving to the North Pole by surface ocean currents and tropical cyclones. The cold, dry Arctic air coming from Siberia picks up heat and moisture from the open oceans, making the sea water denser so that the warm water sinks slowly down to c. 2000 m. A deep-water thermohaline flow (THC) transports the excess hot (c. 18°C) water south to Antarctica. It is replaced by a cold (c. 2°C) surface water from that area. The latter quickly cool western Europe and Siberia, and glaciers start to advance in Greenland within about 10 years. The THC flow decreases in Interglacials, causing the increased build-up of heat in the Northern Hemisphere (c. 60% currently stored in the Atlantic Ocean), and the ice cover in the Arctic Ocean thaws. Several such cycles may take place during a single major cold event.

BMP8 and activated brown adipose tissue in human newborns

The classical dogma states that brown adipose tissue (BAT) plays a major role in the regulation of temperature in neonates. However, although BAT has been studied in infants for more than a century, the knowledge about its physiological features at this stage of life is rather limited. This has been mainly due to the lack of appropriate investigation methods, ethically suitable for neonates. Here, we have applied non-invasive infrared thermography (IRT) to investigate neonatal BAT activity. Our data show that BAT temperature correlates with body temperature and that mild cold stimulus promotes BAT activation in newborns. Notably, a single short-term cold stimulus during the first day of life improves the body temperature adaption to a subsequent cold event. Finally, we identify that bone morphogenic protein 8B (BMP8B) is associated with the BAT thermogenic response in neonates. Overall, our data uncover key features of the setup of BAT thermogenesis in newborns.

The Plenus Cold Event Record in the Abyssal DSDP Site 367 (Cape Verde, Central Atlantic): Environmental Perturbations and Impacts on the Nitrogen Cycle

The Oceanic Anoxic Event 2, at the Cenomanian-Turonian boundary (∼93.9 Ma), was an episode of widespread burial of organic matter in marine sediments, underlined by a positive carbon-isotope (δ13C) excursion observed worldwide. Within this episode of O2-depleted conditions, a short interval of cooling, termed as the Plenus Cold Event, has been recorded in many sites and sections in the northern hemisphere (Tethyan domain, Western Interior Seaway, proto-North Atlantic Ocean). But, its record and its impact on the biogeochemical cycles of carbon and nitrogen in the southern part of Central Atlantic Ocean has not been explored yet. Here, we present a detailed geochemical study of the Deep Sea Drilling Project site 367 (Cape Verde) based on a compilation of previous and new data of carbon and nitrogen isotope signals as well as trace element concentrations. The aim of this study is to better constrain the evolution of oxygenation in the water column and the associated changes in nitrogen cycle before and during the Oceanic Anoxic Event 2 in order to understand the paleoceanographic and environmental consequences of the Plenus Cold Event at one of the deepest site of the Central Atlantic Ocean. Our new dataset improves the resolution of the δ13C curve for this site, and we propose a new chemo-stratigraphic frame of the carbon excursion allowing for a better identification of the short-term negative carbon isotope excursion associated to the Plenus Cold Event. The detailed evolution of redox-sensitive proxies (Mo, U, V, Fe, Cu, Ni enrichments and Corg/Ptotal) and isotopic signals (δ13Corg and δ15Ntotal) evidence that this deep site was impacted by this cooling event. While anoxic conditions prevailed in bottom waters before and during the onset of the Oceanic Anoxic Event 2 characterized by euxinic NH4+-rich water column, this cooling event was accompanied by reoxygenation of the water column, which had affected the behavior of the redox-sensitive elements and caused changes in nitrogen biogeochemical cycling.

Effect of a cold event on population and community of pit-inhabiting sea urchins in Western Pacific coasts

Coastal tide pools in southern Japan are inhabited by the rock-boring sea urchin Echinostrephus molaris, which excavate pits in the substrate. These pits are subsequently used by non-boring sea urchins such as Anthocidaris crassispina and Echinometra sp. B, and the recolonized pits are often inhabited by a commensal limpet-like trochid snail species, Broderipia iridescens. We explored the population and community dynamics of these sea urchins and the limpet-like snail by monitoring occupancy of 512 pits in tide pools in Shirahama, Japan from May 2017–May 2019. Initially, nearly all pits were occupied by any one of the three sea urchin species, but an unusual cold event in February 2018 caused a mass die off of these sea urchins. After this event, occupancy decreased from 99% to 15%, and the tropical species Echinometra sp. B disappeared from the study pools. We observed slow population recovery of E. molaris and A. crassispina, provably via migration of sub-adults from the subtidal zone. Turnover rate of the pit-occupying sea urchin species was <1.0% before the cold event, but drastically increased after the cold event. Population size of the commensal snail decreased along with those of their host, but the rate of commensalism was constant at 50–55% throughout the study period, suggesting that these snails followed their host sea urchins repeating inter-pit migration. Despite mass mortality and slow recovery, the sea urchin density remained high enough to maintain persistent sea urchin barrens throughout the study period.