CO2 Air-Water Exchanges during Seasonal and Glacial Cycles

Based on the photosynthesis-respiration reversible reaction and the available statistics, we attempted to quantify the planetary seasonal exchanges of CO2 between air and water from 1970 and compared them to the glacial ACC cycles as reported from ice cores archives. In 2020, the overall continental absorption (AW) was 8.0 giga tonnes of carbon per year (GtC/y). Emissions into the atmosphere (EW) resulting from mineral degradation by respiration and combustion of biomass and fossil hydrocarbons were 14.7 GtC/y, an increase of 2.4% per year since 1970. The continental surplus balance (-AW+EW) of 6.7 GtC/y was shared between the atmosphere, which received 5.1 GtC/y (GATM), and the ocean which absorbed 1.6 GtC/y. This ocean contribution (OC) corresponded to 17% of the 9.2 GtC/y emissions by combustion of fossil hydrocarbons (EFOS). Analysis of the ACC oscillations during 2020 in the northern hemisphere showed that the ocean absorbed 11.1 GtC during the warm season and outgassed 9.5 GtC during the cold season. Assuming proportionality to world population, the ACC, 414 parts per million (ppm) in 2021, would reach 584 ppm in 2080, still growing at a rate of 0.6% per year. The gain of atmospheric CO2 (GATM) and its absorption by the ocean (OC) were expected to peak at 7.0 and 2.2 GtC/y, respectively, in 2080. This increase in the availability of atmospheric CO2 resulted in improved yields of agriculture which more than compensated for the reduction by half of food-producing areas per capita from 1970.

Comparative population genomics reveals glacial cycles to drive diversifications in tropical montane birds(Aves,Timaliidae)

Many bird species are specialized to live in the broadleaved,evergreen forests in the mountain regions in Southeast Asia.These mountain habitats are not continuously distributed as the different mountain areas are separated by lowlands,which has restricted gene flow and thus contributed to the high biological diversity in this region.The degree of connectivity between mountain areas has fluctuated with the Pleistocene glacial cycles,being largest during the glaciations when the mountain forests spread to lower elevations.Here we study how the intermittent periods of restricted gene flow and connectivity between the populations of five montane species of babblers(Aves,Timaliidae)in Vietnam may be traced in their genomes.The results suggest that the babbler species in the Central Highlands have been isolated from their sister-populations in northern Vietnam for between ca.585 and 380 ky.For two species with populations in both the Central Highlands and the Da Lat region,we found that these split at more or less the same time(440–340 kya).We also found a significant statistical correlation between the time of the splits of these populations and the lowest altitude at which they are known to occur(no similar correlation was found with the geographic distances between populations).The populations in northern Vietnam show higher genetic variation than their counterparts in South-Central Vietnam,supporting the postulate that smaller populations may have lower genetic variation than larger.In accordance with this,we found the lowest genetic variation in the two species with the smallest populations in the Central Highlands.These two populations also show low levels of genomic heterozygosity.Our results show that the south-central populations of the studied babbler species are genetically distinct from their sister-populations in northern Vietnam,providing additional argument for the long-term protection of the evergreen mountain forests in Southeast Asia.

Late Quaternary eolian records in the northwest Pacific with glacial cycles: a comparison

Two deep-sea cores in the northwest Pacific have been analysed for sedimentology, mineralogy and environmental magnetism. The results show that after eliminating the interference from volcanism, several proxies such as quartz content, mass susceptibility and anhysteretic magnetic remanence can be used to indicate the eolian deposit from East Asia, and provide information on paleo-atmospheric circulation. A comparison of eolian record in Cure RC10-175 with its oxygen isotopic curve has revealed that the peaks of eolian accumulation occurred at the climatic “optimum” of the Holocene and the last interglaciation, showing the fairly complex nonlinear relationship between continental/pelagic eolian records and the global glacial cycles as well as within the climatic and environmental system.

Glacial Thermohaline Circulation and Climate:Forcing from the North or South?

Based on the evidence available from both observations and model simulations, the author proposes a view that may provide a unified interpretation of the North Atlantic thermohaline variability. Because of the slow response time of the Southern Ocean （millennia） and the relatively faster response time of the North Atlantic （centuries）, the North Atlantic thermohaline circulation is controlled predominantly by the climate forcing over the Southern Ocean at the long glacial cycle timescales, but by the North Atlantic climate forcing at the short millennial timescaies.

How to Heat a Planet? Impact of Anthropogenic Landscapes on Earth’s Albedo and Temperature

Today anthropogenic climate change is underway and predicted future global temperatures vary significantly. However, the drivers of current climate change and their links to Earth’s natural glacial cycle have yet to be fully resolved. Currently, many on a local level understand, and are exposed to, the heat energy generated by what’s referred to as the urban heat island effect (UHI), whereby natural flora with higher albedos is replaced by manmade urban areas with lower albedos. This heat effect is not constrained to these regions and all anthropogenic surfaces with lower albedos need to be studied and quantified as the accumulated additional heat energy (infrared energy) is trapped within Earth’s atmosphere and could affect the Earth on a planetary level. Deployed satellites have detected critical changes to Earth’s albedo to lower levels, however the cause and impact of these changes have yet to be fully understood and incorporated into Global Circulation models (GCMs). Here it’s shown that industrialization of anthropogenic landscape practices of the past century has displaced millions of square kilometres of naturally high albedo grasslands with lower albedo agricultural landscapes. Utilising a fundamental Energy Balance Model, (EBM) it’s demonstrated these specific changes have generated vast amounts of additional heat energy which is trapped by the atmosphere, transferred and stored within the oceans of the Earth as shown in Figure 1. The total additional heat energy accumulated over the preceding 110 years correlates to that required to warm the Earth to the levels seen to date, altering Earth’s overall energy budget. This energy will continue to accumulate and warm the Earth to a predicted 1.60 ± 0.20 Celsius by 2050 over 1910 levels. These findings are independent of anthropogenic Greenhouse Gas (GHG) additions and are further validated by predicting Earth’s temperature and albedo at the last glacial maxima, suggesting that an albedo cycle aligned to Gaia theory is the primary driver of Earth’s natural climate cycle.

Transition of Quaternary glacial cyclicity in deep-sea records at Nansha,the South China Sea

High-resolution oxygen isotope records over the last 2249 ka (MIS 1-86) have been obtained from cores of the upper section (105.08 m) at ODP Site 1143 (water depth of 2772 m)drilled in the Nansha area, southern South China Sea. The sampling resolution is at about 2 ka intervals, resulting in one of the best oxygen isotope records over the global ocean. The oxygen isotope curves, displaying details in the Pleistocene glacial cycles, have revealed a nearly 300 ka long stage of transition from a predominant 40 ka to 100 ka periodicity. Therefore, the 'Mid-Pleistocene Revolution' should be considered as a process of transition rather than an abrupt change. Within the 100 ka glacial cycles, the changes in tropical sea surface water were found to lead those in high-latitude ice sheet. Our comparisons show that the ice sheet expansion and the glacial stage extension in the Northern Hemisphere with the 100 ka cycles must have been driven not by ice sheet itself, but by processes outside the high latitudes of the Northern Hemisphere.

Geochemistry of rare earth elements in the mid-late Quaternary sediments of the western Philippine Sea and their paleoenvironmental significance

Based on a δ180 chronology, rare earth elements （REE） and other typical elements in sediments from core MD06-3047 in the western Philippine Sea were analyzed to constrain the provenances of the sediments and investigate quantitative changes in the Asian eolian input to the study area over the last 700 ka. Among the competing processes that might affect REE compositions, sediment provenance is the most important one. Provenance analysis suggests that the study sediments have two provenance end-members; local volcanic sources are dominant, and eolian dust from the Asian continent has a smaller contribution. During glacial periods, eolian input to the western Philippine Sea was enhanced. In contrast, material supply from local volcanics in- creased during interglacial periods. Changes in eolian input to the study area were probably related to the strength of the East Asian winter monsoon （EAWM） as well as aridity in the Asian continent on an orbital time scale, and were partly influenced by local control factors on shorter time scales. Therefore, we propose that the present study expands the application of the REE-based method for quantitatively estimating the eolian component from the mid-latitude northern Pacific to the low-latitude western Pacific. Additionally, the study preliminarily confirms the influence of EAWM-transported eolian materi- al on sedimentation in the western Philippine Sea since 700 ka.

Organic carbon isotope and molecular fossil records of vegetation evolution in central Loess Plateau since 450 kyr

Significant uncertainties remain regarding the temporal evolution of natural vegetation during the Quaternary, and drivers of past vegetation change, on the Chinese Loess Plateau （CLP）. This study presents analyses of total organic carbon isotopic composition （TOC） and n-alkane ratios （C31/C27） from the Lingtai loess-palaeosol sequence on the central CLP over the last 450 kyr. The results demonstrate that the vegetation in this region comprised a mix of C3 and C4 plants of herb and woody growth-form. C3 plants dominated for most of the last 450 kyr, but this did not lead to extensive forest. C3 woody plants were more abundant in MIS9 （S3 period） and MIS5 （S 1 period） during warm and humid climate conditions. Herbs increased in the region since 130 kyr, possibly as a result of increased aridity. On the orbital timescales, there was a reduction of C3 herbal plants in MIS 11 （$4） than in M1S 12 （L5）, and in Holocene than in the last glacial period. Our isotope and n-alkane proxy records are in agreement with Artemisia pollen changes in the region, which is/was the dominant species in this area and varying due to different heat and water conditions between glacial and interglacial periods. Though the climate in MIS1 （SO） was similar to that in MIS11 （S4）, a significant increase in woody plants during the Holocene suggests the impact of human activities and ecological effects of changes in fire activity.