Temporal Variability of Ventilation in the Eurasian Arctic Ocean

The Arctic Ocean plays an important role in the regulation of the earth's climate system, for instance by storing large amounts of carbon dioxide within its interior. It also plays a critical role in the global thermohaline circulation, transporting water entering from the Atlantic Ocean to the interior and initializing the southward transport of deep waters. Currently, the Arctic Ocean is undergoing rapid changes due to climate warming. The resulting consequences on ventilation patterns, however, are scarce. In this study we present transient tracer (CFC-12 and SF6) measurements, in conjunction with dissolved oxygen concentrations, to asses ventilation and circulation changes in the Eurasian Arctic Ocean over three decades (1991–2021). We constrained transit time distributions of water masses in different areas and quantified temporal variability in ventilation. Specifically, mean ages of intermediate water layers in the Eurasian Arctic Ocean were evaluated, revealing a decrease in ventilation in each of the designated areas from 2005 to 2021. This intermediate layer (250–1,500 m) is dominated by Atlantic Water entering from the Nordic Seas. We also identify a variability in ventilation during the observation period in most regions, as the data from 1991 shows mean ages comparable to those from 2021. Only in the northern Amundsen Basin, where the Arctic Ocean Boundary Current is present at intermediate depths, the ventilation in 1991 is congruent to the one in 2005, increasing thereafter until 2021. This suggests a reduced ventilation and decrease in the strength of the Boundary Current during the last 16 years. Key Points Temporal variability of ventilation in the Eurasian Arctic Ocean during the past 30 years is estimated by observations of transient tracers We found a slow down of the ventilation between 2005 and 2021 in the intermediate waters Evidence of multidecadal variability of ventilation in the intermediate waters of the Eurasian Arctic Ocean is present Plain Language Summary The Eurasian Arctic Ocean, the region of the Arctic Ocean connected to the European and Asian continents, is an important pathway for recently ventilated water from the Nordic Seas. These waters are exported back to the North Atlantic following their travel through the Arctic Ocean. Ventilation describes the process of surface waters being transported into the interior ocean due to increasing density, which affects the underlying water masses. In this study we investigate how the ventilation patterns have evolved in the Eurasian Arctic Ocean over the past three decades, using transient tracer (CFC-12 and SF6) measurements. We observed a significant change in the intermediate layer (250–1,500 m) with older waters found in measurements in 1991 and 2021 compared to 2005 and 2015. Moreover, our data suggest a slowdown in ventilation throughout the three decades in the northern Amundsen Basin, implying a decrease in the circulation time-scale of the Arctic Ocean Boundary Current over the past 16 years. This has potentially important implications for the transport of, for example, heat, salt or oxygen from the Atlantic Ocean around the Arctic Ocean, and back

Physical Oceanography during ODEN expedition SO21 for the Synoptic Arctic Survey

Hydrographic (CTD) profiles of Temperature, Salinity, Dissolved Oxygen, Chlorophyll A fluorescence and Coloured Dissolved Organic Matter (CDOM) collected in the Arctic Ocean, over the western Eurasian Basin and Lomonosov Ridge, between 2 August and 11 September 2021, from I/B Oden. This is the Swedish contribution to the international Synoptic Arctic Survey. This dataset merges the full-depth physical CTD and the shallow biological CTD profiles. Both systems had the standard SeaBird SBE911 plus system with dual sensors to measure in-situ temperature and conductivity and single sensors measuring pressure and oxygen. The physical CTD also had a CDOM sensor (Turner Cyclops fluorometer), while the Chl-A fluorometer (WET Labs, ECO-AFL/FL) was moved throughout the expedition between the two systems. Salinity, Oxygen, Chl-A fluorescence and CDOM were calibrated against sample data collected and analysed by the co-authors: - Salinity samples from the deep stations were analysed post-cruise using a salinometer (Guildline Autosal) and IAPSO standard seawater at the GEOMAR, Germany. - Dissolved oxygen was determined onboard using an automatic Winkler titration setup with UV detection (Scripps Institute of Oceanography Oxygen Titration System version 2.35m). - Chl-A concentration was determined post-cruise from flow cytometry (FCM) at Linnaeus University, Sweden. The samples consisted of 4 mL cryovials, of which 3.8 mL was sample water and 76 μL 25% EM grade glutaraldehyde solution (Glu stock). The samples incubated at room temperature for 5 minutes before flash freezing in liquid nitrogen and then placing in the -80 °C freezer in cryoboxes. - CDOM was determined post-cruise at the National Institute of Aquatic Resources - DTU Aqua, Denmark, following the method of Lawaetz and Stedmon (2009) This dataset contains the 1-m bin-averaged profiles. For more information about each sensor and their calibration, the reader is invited to check the cruise report (final version submitted on 20 September; shareable version with DOI coming soon

Physical Oceanography measured on bottle water samples during ODEN expedition SO21 for the Synoptic Arctic Survey

Discrete bottle values of Temperature, Salinity, Dissolved Oxygen, Chlorophyll A fluorescence and Coloured Dissolved Organic Matter (CDOM) collected in the Arctic Ocean, over the western Eurasian Basin and Lomonosov Ridge, between 2 August and 11 September 2021, from I/B Oden. This is the Swedish contribution to the international Synoptic Arctic Survey. This dataset merges the bottle data from the full-depth physical CTD and the shallow biological CTD. Both systems had the standard SeaBird SBE911 plus system with dual sensors to measure in-situ temperature and conductivity and single sensors measuring pressure and oxygen. The physical CTD also had a CDOM sensor (Turner Cyclops fluorometer), while the Chl-A fluorometer (WET Labs, ECO-AFL/FL) was moved throughout the expedition between the two systems. Salinity, Oxygen, Chl-A fluorescence and CDOM were calibrated against sample data collected and analysed by the co-authors: - Salinity samples from the deep stations were analysed post-cruise using a salinometer (Guildline Autosal) and IAPSO standard seawater at the GEOMAR, Germany. - Dissolved oxygen was determined onboard using an automatic Winkler titration setup with UV detection (Scripps Institute of Oceanography Oxygen Titration System version 2.35m). - Chl-A concentration was determined post-cruise from flow cytometry (FCM) at Linnaeus University, Sweden. The samples consisted of 4 mL cryovials, of which 3.8 mL was sample water and 76 μL 25% EM grade glutaraldehyde solution (Glu stock). The samples incubated at room temperature for 5 minutes before flash freezing in liquid nitrogen and then placing in the -80 °C freezer in cryoboxes. - CDOM was determined post-cruise at the National Institute of Aquatic Resources - DTU Aqua, Denmark, following the method of Lawaetz and Stedmon (2009) This dataset contains the bottle data of the casts where bottles were fired. For more information about each sensor and their calibration, the reader is invited to check the cruise report (final version submitted on 20 September; shareable version with DOI coming soon

Deep inflow transport and dispersion in the Gulf of St. Lawrence revealed by a tracer release experiment

The Gulf of St. Lawrence is increasingly affected by bottom water hypoxia; however, the timescales and pathways of deep water transport remain unclear. Here, we present results from the Deep Tracer Release eXperiment (TReX Deep), during which an inert SF 5 CF 3 tracer was released inshore of Cabot Strait at 279 m depth to investigate deep inflow transport and mixing rates. Dispersion was also assessed via neutrally-buoyant Swish floats. Our findings indicate that the tracer moves inland at 0.5 cm s −1 , with an effective lateral diffusivity of 2 × 10 2 m 2 s −1 over 1 year. Simplified 1D simulations suggest inflow water should reach the estuary head in 1.7 years, with the bulk arriving after 4.7 years. Basin-wide effective vertical diffusivity is around 10 −5 m 2 s −1 over 1 year; however, vertical diffusivity increases near the basin slopes, suggesting that turbulent boundary processes influence mixing. These results are compared to Lagrangian simulations in a regional 3D model to evaluate the capacity to model dispersion in the Gulf

Western Subpolar North Atlantic transport variability, Cruise No. MSM94, 02. August - 06. September 2020, Emden (Germany) - Emden (Germany)

SPNA transport 2020 The scientific program of the MARIA S. MERIAN MSM94 expedition was dedicated to studies on the intensity of water mass transformation and the transport of water masses in the boundary current systems off Labrador and at the southwestern tip of Greenland. During the expedition we redeployed 11 moorings and recovered 1 bottom lander. Measurements of the vertical structure of temperature, salinity, density, oxygen, optical properties and the flow along selected sections have been surveyed during the MSM94 expedition. Close to the surface, permanent registrations are carried out with the thermosalinograph (temperature, salinity) and meteorological data are continuously collected. Flow measurements up to 1000m depth are performed with the ships installed ADCPs. Argo floats (IFREMER, BSH) and surface drifter (NOC, UK) were also deployed. The expedition is a contribution to international projects (OSNAP, Blue Action, EuroSea). The expedition was conducted during the COVID-19 pandemic and modifications to the science program had to be applied (e.g. Start/end-port Emden, Germany, reduced science crew and respective cut’s in data acquisition)

The COP9 signalosome mediates transcriptional and metabolic response to hormones, oxidative stress protection and cell wall rearrangement during fungal development

The COP9 signalosome complex (CSN) is a crucial regulator of ubiquitin ligases. Defects in CSN result in embryonic impairment and death in higher eukaryotes, whereas the filamentous fungus Aspergillus nidulans survives without CSN, but is unable to complete sexual development. We investigated overall impact of CSN activity on A. nidulans cells by combined transcriptome, proteome and metabolome analysis. Absence of csn5/csnE affects transcription of at least 15% of genes during development, including numerous oxidoreductases. csnE deletion leads to changes in the fungal proteome indicating impaired redox regulation and hypersensitivity to oxidative stress. CSN promotes the formation of asexual spores by regulating developmental hormones produced by PpoA and PpoC dioxygenases. We identify more than 100 metabolites, including orsellinic acid derivatives, accumulating preferentially in the csnE mutant. We also show that CSN is required to activate glucanases and other cell wall recycling enzymes during development. These findings suggest a dual role for CSN during development: it is required early for protection against oxidative stress and hormone regulation and is later essential for control of the secondary metabolism and cell wall rearrangemen

Influence of soil phosphorus and manure on phosphorus leaching in Swedish topsoils

In Sweden, subsurface transport of phosphorus (P) from agricultural soils represents the primary pathway of concern for surface water quality. However, there are mixed findings linking P in leachate with soil P and limited understanding of the interactive effects of applied P sources and soil test P on P leaching potential. Identifying soils that are susceptible to P leaching when manure is applied is critical to management strategies that reduce P loadings to water bodies. Intact soil columns (20 cm deep) from five long-term fertilization trials across Sweden were used in leaching experiments with simulated rainfall to explore the interactive effects of dairy cow (Bos taurus L.) manure application, soil test P and cropping system. Strong relationships were observed between ammonium-lactate extractable P in soil and dissolved reactive P (DRP) concentrations in leachate, although regression slopes varied across soils. For three soils, application of manure (equal to 21-30 kg P ha-1) to the soil columns significantly increased DRP leaching losses. The increase in DRP concentration was correlated to soil test P, but with wide variations between the three soils. For two soils leachate P concentrations after manure addition were independent of soil P status. Despite variable trends in P leaching across the different soils, P concentrations in leachate were always moderate from soils at fertilization rates equivalent to P removal with harvest. Results clearly stress the importance of long-term P balance to limit P leaching losses from Swedish agricultural soils

Variability and Trends in Physical and Biogeochemical Parameters of the Mediterranean Sea during a Cruise with RV MARIA S. MERIAN in March 2018

info:eu-repo/semantics/publishe