Alfred Wegener Institute for Polar and Marine Research
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Marine heatwaves intensification, expansion and departure into the permanent state over the Tropical Indian Ocean: A regional earth system model assessment
Get PDFThis study employed a regional earth system model, namely ROM over the CORDEX-SA domain, to investigate the future changes in the Marine heatwaves (MHWs) with respect to the historical baseline period (1976–2005) in the three time-slices, explicitly, near future (NRF; 2010–2039), middle future (MDF;2040–2069), and far future (FRF; 2070–2099) under two emission scenarios, Representative Concentration Pathway (RCP4.5 and RCP8.5). For the historical period, ROM showed a reasonable agreement with observed MHWs metrics and their trends and outperformed the forcing General Circulation Model and Multi-Model Ensemble of CMIP5 models. The future MHWs are expected to increase in intensity and duration. The continuous lengthening of MHWs duration leads to a permanent MHW state condition with strong spatial variability in its appearance. The first permanent MHW will emerge in both RCPs, while the absolute permanent MHW state is mainly visible in RCP8.5. The genesis and augmentation in the MHWs intensity is associated with local air-sea fluxes, however, in the long term, the increase in the mean SST in the future led to the rise of MHWs activity. The diagnosis of El Niño Southern Oscillation teleconnection and Indian Ocean Dipole on the MHWs is investigated. During the El Niño regime, not only did the proportion of the Tropical Indian Ocean experiencing MHWs increase but also an increase in the intensity is evident. IOD controls the MHWs metrics in the proximity of the western box and eastern box during its positive and negative phases
Vulnerability assessment of Arctic coastal communities to the effects of coastal erosion and permafrost warming.
Get PDFThis study assesses the escalating vulnerability of Arctic coastal communities due to the combined impacts of coastal erosion and permafrost warming. With the Arctic experiencing heightened temperatures, coastal permafrost areas face increased instability, endangering vital infrastructures. The study focuses on a pan-Arctic evaluation of settlements and infrastructures at risk, enhancing the existing Arctic coastal infrastructure dataset (SACHI) to include road types, airstrips, and artificial water reservoirs.
By analyzing coastline change rates from 2000 to 2020, alongside permafrost ground temperature and active layer thickness trends from the ESA Permafrost Climate Change Initiative datasets, the research identifies settlements at risk for the years 2030, 2050, and 2100. The accuracy of the dataset is rigorously evaluated. Results indicate that by 2100, 23% of coastal settlements will face the impacts of coastal erosion. Projections based on linear trends suggest an 8°C increase in coastal permafrost ground temperature and a 0.9-meter growth in active layer thickness by the same year.
Crucially, the study reveals that 65% of all infrastructures and settlements will be affected by permafrost warming within the range of 5-15&#176;C, with 35% experiencing active layer thickening between 1-5 meters. This research marks the first regional-scale identification of settlements at risk from coastal erosion along Arctic and permafrost-dominated coasts in the northern hemisphere. The findings emphasize the urgency of adapting to current and future environmental changes to mitigate the deterioration of living conditions in permafrost coastal settlements. Immediate action is imperative to counteract these challenges and ensure the resilience of these vulnerable communities.</jats:p
Rapid Down‐Slope Transport of Fresh Dissolved Organic Matter to the Deep Ocean in the Eastern North Atlantic
No full textIntense convective mixing in the central North Atlantic is a major gateway for dissolved organic matter (DOM) into the deep ocean, sustaining elevated dissolved organic carbon (DOC) concentrations. Rapid down-slope transport on adjacent Irish and Hebrides Margins represents another, less-explored mechanism contributing to the deep-sea DOM reservoir. Our analyses of solid-phase extractable DOM (SPE-DOM) in bottom waters in this region showed 7–11 μM higher DOC concentration and 190–330 years youngerSPE-DOM radiocarbon ages compared to similar depths in the open eastern North Atlantic. We estimated a down-slope DOC flux of 43 Tg C yr−1 from the Irish and Hebrides shelves. During transport, conservative mixing, dominated by physical rather than biological/chemical processes, determined the molecular DOM composition, while minor particulate organic matter degradation introduced less-refractory DOM with terrigenous characteristics. Thus, rapid down-slope transport emerges as an efficient conduit for delivering fresh DOM into the deep ocean
Arctic freshwater anomaly transiting to the North Atlantic delayed within a buffer zone
Get PDFAbstractA two-decade-long accumulation of freshwater in the Arctic Ocean’s Beaufort Gyre has recently started to be released. Here we use satellite observations and model simulations to show that changes in wind regimes and sea ice declines are causing freshwater to accumulate close to the export gateways to the North Atlantic. This emerging buffer zone plays an important role in modulating the propagation of freshwater into the subpolar North Atlantic.</jats:p
Full mission evaluation of EnMAP water leaving reflectance products using three atmospheric correction processors
Get PDFThis study presents what we believe is the first extensive assessment of the water
reflectance products from the German hyperspectral Environmental Mapping and Analysis
Program (EnMAP). We evaluate EnMAP’s standard normalized water leaving reflectance [ρ W]N
over 17 water sites in the first two years of the mission. The EnMAP [ρ W]N standard product is
generated by a dedicated water atmospheric correction (AC) called the Modular Inversion Program
(MIP). The quality of the [ρ W]N retrievals was assessed using in situ hyperspectral measurements
and Aerosol Robotic Network - Ocean Colour (AERONET-OC) multispectral measurements.
The results showed very good agreement between in situ hyperspectral match-ups and EnMAP [ρ
W]N, with an underestimation of EnMAP of −17.37% (bias, β) and an error (ϵ) of 23.75% at 418 –
797 nm. Two other AC processors were also investigated: the polynomial based algorithm applied
to MERIS (Polymer) and the atmospheric correction for OLI lite (Acolite). The intercomparison
exercise between the three AC methods applied to EnMAP data using the hyperspectral match-up
dataset showed better statistical metrics for MIP (ϵ = 23%, β = −17.37%) compared to Polymer
(ϵ = 42.20%, β = −2.43%) and Acolite (ϵ = 97%, β = 97%). The superior performance of MIP
was further confirmed by the validation results obtained with the multispectral match-up dataset;
MIP retrievals show good agreement with in situ measurements at the majority of study sites
Manganese reduction and associated microbial communities in Antarctic surface sediments
Get PDFThe polar regions are the fastest warming places on earth. Accelerated glacial melting causes increased supply of nutrients such as metal oxides (i.e., iron and manganese oxides) into the surrounding environment, such as the marine sediments of Potter Cove, King George Island/Isla 25 de Mayo (West Antarctic Peninsula). Microbial manganese oxide reduction and the associated microbial communities are poorly understood in Antarctic sediments. Here, we investigated this process by geochemical measurements of in situ sediment pore water and by slurry incubation experiments which were accompanied by 16S rRNA sequencing. Members of the genus Desulfuromusa were the main responder to manganese oxide and acetate amendment in the incubations. Other organisms identified in relation to manganese and/or acetate utilization included Desulfuromonas, Sva1033 (family of Desulfuromonadales and unclassified Arcobacteraceae. Our data show that distinct members of Desulfuromonadales are most active in organotrophic manganese reduction, thus providing strong evidence of their relevance in manganese reduction in permanently cold Antarctic sediments
Evolution of a buried moat-drift system within the Ewing Terrace uncovering highly dynamic bottom currents at the Argentine Margin during Early Oligocene to Middle Miocene
No full textThe Ewing Terrace is a relatively flat surface formed by the action of bottom currents and part of a Contourite Depositional System (CDS) at the Argentine continental slope. It is situated in a highly complex oceanographic setting at the Brazil-Malvinas Confluence Zone. Located in water depths of approx. 1000 – 1200 m and incised by the Mar del Plata Canyon, the Ewing Terrace is separated into the Northern Ewing Terrace (NET) and the Southern Ewing Terrace (SET). The long-term variations in ocean circulation led to a complex internal architecture of the terrace. As a result, this region represents a unique archive for studying sedimentary features that were eroded, transported, and deposited by along- and down-slope processes. An in-depth data analysis of high-resolution multichannel seismic profiles exhibits a complex sequence of erosional and depositional contouritic features, namely buried moat-drift systems identified in depths of approx. 370-750 m below the seafloor. They are arranged in migrating sequences and clustered in the Early Oligocene to Middle Miocene. This pattern is probably attributable to the vertical shift of water masses and to a highly dynamic oceanographic setting with spatial changes influenced by the Brazil-Malvinas Confluence Zone over this particular geological time. The moat-drift systems reveal significant lateral changes from north to south. In the southern area of the SET the moats are constructional and the associated separated mounded drifts are well developed. In contrast, the northern area exhibits two types of moats, reminiscent of cut-and-fill structures that mirror the significant and rapid changes in bottom current dynamics. With these new insights, this study contributes to a better understanding of moat-drift systems and improves the knowledge about past oceanographic dynamics and sediment deposition at the northern Argentine margin.</jats:p
Evolutionary genomics of the emergence of brown algae as key components of coastal ecosystems
Get PDFBrown seaweeds are keystone species of coastal ecosystems, often forming extensive underwater forests, and are under considerable threat from climate change. In this study, analysis of multiple genomes has provided insights across the entire evolutionary history of this lineage, from initial emergence, through later diversification of the brown algal orders, down to microevolutionary events at the genus level. Emergence of the brown algal lineage was associated with a marked gain of new orthologous gene families, enhanced protein domain rearrangement, increased horizontal gene transfer events, and the acquisition of novel signaling molecules and key metabolic pathways, the latter notably related to biosynthesis of the alginate-based extracellular matrix, and halogen and phlorotannin biosynthesis. We show that brown algal genome diversification is tightly linked to phenotypic divergence, including changes in life cycle strategy and zoid flagellar structure. The study also showed that integration of large viral genomes has had a significant impact on brown algal genome content throughout the emergence of the lineage
Remote Sensing Earth’s Cryosphere with 0.5-2.0 Ghz Microwave Radiometry: Recent Updates
Get PDFRecent updates in the use of 0.5-2 GHz microwave radiometry for remotely sensing Earth's cryosphere are reported. These updates concern measurements and modeling of the spectral properties of brightness temperatures for geophysical regions such as ice sheets, sea ice, ice shelves, and others. The results are intended to support the continued development of 0.5-2 GHz passive microwave mission concepts for future deployment in space