One major consequence of global warming in the Antarctic region is increased ice-free zones. Subsequent colonization of these ice-free areas by penguins alters their biogeochemistry, with one prominent example being elevation of inorganic phosphate concentrations around feces depositions. The complex soil biochemistry in the region makes it difficult to define the causal factors of these changes using common research approaches. Here, we addressed the effects of phosphate alone on microbiome structure and dynamics over time by adding external phosphate to selected soils in the Antarctic region. We then analyzed the soil bacterial community composition and diversity using 16S rRNA amplicon sequencing and compared these data with phosphate levels. Parallel geochemical analysis revealed changes in nine soil geochemical factors upon phosphate addition, all of which were relevant to microbiome structure, with soil pH showing the highest correlation. Links between geochemical factors and composition were identified, as were interactions between bacterial taxa. Additionally, Sphingobacteriia, Sphingobacteriales and Chitinophagaceae were found to be more abundant in phosphate-treated soils. Co-occurrence network analysis revealed significantly increased levels of associations in all major network properties over time after phosphate supplementation. Therefore, we conclude phosphate addition has diverse effects on Antarctic soil microbiomes.
The China Meteorological Administration recently released China Polar Climate Change Annual Report(2022)in Chinese,with the following main conclusions.Using the China Reanalysis-40 dataset(CRA-40),rapid warming has been observed in the Antarctic Peninsula and West Antarctica since 1979,with some parts of East Antarctica also experiencing warming.In 2022,the regional average temperature in Antarctica based on observational data was close to the long-term average(1991-2020).The Arctic,on the other hand,has experienced a warming trend at a rate of 0.63 ℃ per decade from 1979 to 2022 based on CRA-40,which is 3.7 times the global mean during the same period(0.17 ℃ per decade).In 2022,the overall temperature in the Arctic,using station data,was 1.10 ℃ above the long-term average(1991-2020).In recent years,both the Antarctic and Arctic regions have witnessed an increase in the frequency and intensity of extreme weather events.In 2022,based on the sea ice extent from National Snow and Ice Data Center,USA,Antarctic sea ice reached its lowest extent on record since 1979,and on 18 March,the most rapid surface warming event ever recorded on Earth occurred in the Antarctic,with a temperature increase of 49 ℃ within 3 d.This report has been integrated into China's National Climate Change Bulletin system,to contribute to raising public awareness of polar climate change and providing valuable scientific references to address climate change.
The firn aquifer beneath the Greenland Ice Sheet may play a significant role in rising sea level.Both traditional mechanical drilling and electric thermal drilling are poorly adapted for effective,low-disturbance sampling in firn aquifers.We propose using a vibrocoring technique for the undisturbed sampling of dry firn and firn aquifer layers.A remote-controlled vibrocorer is designed to obtain 1-m-long cores with a diameter of 100 mm.The depth capacity of the system is approximately 50 m.The total weight of the vibrocoring system with the surface auxiliary equipment is approximately 110 kg,and corer assembly itself weighs～60 kg.
Ice-shelf rifts are precursors of glacier calving,and thus they serve as indicators of ice shelf instability,especially under oceanic and atmospheric warming conditions.Therefore,understanding the dynamic processes underlying rift propagation and the associated damage mechanisms is essential to evaluate ice-shelf instability and to predict glacier calving.In this study,we investigated the effect of marginal weakening on rift propagation on the ice shelf of the Petermann Glacier,among the largest in Greenland,during 2016-2022.First,we analyzed satellite optical images to monitor rift growth(length and width)by tracking the tip trajectory of three large rifts identified on the Petermann Ice Shelf.Then,we estimated rift depth using ArcticDEM and ICESat-2 data.Our results indicated consistent increases of the rift widths and depths over the study period,with mean values of 133 m·a-1 and 0.3 m·a-1,respectively.We also combined remote-sensing observations with an ice-sheet numerical model to calculate the stress and damage fields on the Petermann Ice Shelf and to assess the ice shelf margin stability and strength.We determined that damage and lateral shear in the fracture zone degraded ice shelf integrity by decreasing the contact length with the fjord wall.In conclusion,marginal weakening effectively promoted rift propagation on the Petermann Ice Shelf,increasing the risk of future glacier calving.
Greenland and Antarctic ice sheets are the largest potential contributors to global sea level rise (GSLR), amounting to more than 64 m of sea level equivalence (SLE). Between the two, Greenland Ice Sheet (GrIS) alone comprises about 7 m SLE, with a much faster speed of ablation than the Antarctic Ice Sheet. The contribution of GrIS to GSLR has increased from 5％ in the early 1990s to about 25％ in the recent decade (Chen et al., 2017), with an accelerating rate of approximately 0.65 mm·a-1 (Frederikse et al., 2020).
