Explore the vast range of titles available.

Interannual climate changes and increasing atmospheric CO2 (AtmCO2) have significantly altered sea surface partial pressure of CO2 (pCO2) in the Beaufort Sea (BS). Yet, their decadal variability and underlying mechanisms remain inadequately understood. Using observational data and the Regional Arctic System Model (RASM), a decreasing trend transition of the BS summer surface pCO2 was identified at around 2010–2012. Sensitivity cases reveal that the decadal trend transition in surface pCO2 (early: 4.12 ± 0.80 μatm/yr, p < 0.05 and late: 1.23 ± 2.22 μatm/yr, p > 0.05) is driven by interannual climate changes. While the long-term increase in AtmCO2 does not directly drive surface pCO2 trend transition, it reduces its magnitude. The sensitivity experiment with no interannual AtmCO2 changes from 1990 reveals that the statistically significant contributor of the decadal trend transition in surface pCO2 is the concurrent transition in sea ice concentration (SIC, early: −0.0120 ± 0.0037/yr, p < 0.05 and late: 0.0101 ± 0.0063/yr, p > 0.05). The decadal trend transitions in the subsurface and deep layer pCO2 are negligible compared to that in the sea surface pCO2 due to the insignificant influence of interannual climate changes on subsurface and deep layer pCO2. The surface pCO2 decadal trend transition is significantly correlated with a trend transition of CO2 sink. On seasonal timescales, the effects of SIC on the decadal trend transition of pCO2 occur primarily within the duration of open-water (DOW), and align with the decadal trend transitions in the open-water start day, end day, and DOW. The magnitude of sea surface pCO2 trend transition increases as the magnitude of the DOW trend transition increases.

Rapid climate warming and sea-ice loss have induced major changes in the sea surface partial pressure of CO2 (pCO2). However, the long-term trends in the western Arctic Ocean are unknown. Here we show that in 1994–2017, summer pCO2 in the Canada Basin increased at twice the rate of atmospheric increase. Warming and ice loss in the basin have strengthened the pCO2 seasonal amplitude, resulting in the rapid decadal increase. Consequently, the summer air–sea CO2 gradient has reduced rapidly, and may become near zero within two decades. In contrast, there was no significant pCO2 increase on the Chukchi Shelf, where strong and increasing biological uptake has held pCO2 low, and thus the CO2 sink has increased and may increase further due to the atmospheric CO2 increase. Our findings elucidate the contrasting physical and biological drivers controlling sea surface pCO2 variations and trends in response to climate change in the Arctic Ocean.Surface CO2 concentrations in the western Arctic Ocean differ due to local processes. During the period 1994–2017, the Canada Basin has shown rapid increases as warming and ice loss enhance air–sea exchange of CO2, whereas the Chukchi Shelf has strong biological activity, resulting in a CO2 sink.

Mesoscale eddies are structures of seawater motion with horizontal scales of tens to hundreds of kilometers, impact depths of tens to hundreds of meters, and time scales of days to months. This study presents a statistical analysis of mesoscale eddies in the South China Sea (SCS) from 1993 to 2021 based on eddies extracted from satellite remote sensing data using the vector geometry eddy detection method. On average, about 230 eddies with a wide spatial and temporal distribution are observed each year, and the numbers of CEs (52.2%) and AEs (47.8%) are almost similar, with a significant correlation in spatial distribution. In this article, eddies with a lifetime of at least 28 days (17% of the number of total eddies) are referred to as strong eddies (SEs). The SEs in the SCS that persist for several years in similar months and locations, such as the well-known dipole eddies consisting of CEs and AEs offshore eastern Vietnam, are defined as persistent strong eddies (PSEs). SEs and PSEs affect the thermohaline structure, current field, and material and energy transport in the upper ocean. This paper is important as it names the SEs and PSEs, and the naming of eddies can facilitate research on specific major eddies and improve public understanding of mesoscale eddies as important oceanic phenomena.

Over the past three decades, increasing atmospheric CO2 (AtmCO2) has led to climate warming, sea ice reduction and ocean acidification in the Beaufort Sea (BS). Additionally, the effects of upwelling on the carbon cycle and acidification in the BS are still unknown. The Regional Arctic System Model (RASM) adequately reflects the observed long-term trends and interannual variations in summer sea ice concentration (SIC), temperature, partial pressure of CO2 (pCO2) and pH from 1990 to 2020. Multiple linear regression results from a control case show that surface (0–20 m) pH decline is significantly driven by AtmCO2 and SIC, while AtmCO2 dominates in subsurface (20–50 m) and deep layers (50–120 m). Regression results from a sensitivity case show that even if the AtmCO2 concentration remained at 1990 levels, the pH would still exhibit a long-term decline trend, being significantly driven by SIC only in the surface layers and by SIC and net primary production (NPP) in the subsurface layers. In contrast to the nearly linearly increasing AtmCO2 over the last three decades, the ocean pH shows more interannual variations that are significantly affected by SIC and mixed layer depth (MLD) in the surface, NPP and Ekman pumping velocity (EPV) in the subsurface and EPV only in the deep layer. The comparison of results from high and low SIC years reveals that areas with notable pH differences are overlapping regions with the largest differences in both SIC and MLD, and both cause a statistically significant increase in pCO2 and decrease in pH. Comparison of results from high and low EPV years reveals that although stronger upwelling can lift up more nutrient-rich seawater in the subsurface and deep layers and lead to higher NPP and pH, this effect is more than offset by the higher DIC lifted up from deep water, leading to generally lower pH in most regions.

Rapid warming and sea-ice loss in the Arctic Ocean are among the most profound climatic changes to have occurred in recent decades on Earth. Arctic Ocean biological production appears that it may be increasing as a result, but the consequences for nutrient concentrations are unknown. We have assembled a collection of historical field data showing that average concentrations of the macronutrients nitrate and phosphate have decreased by 79% and 29%, respectively, in surface waters of the western Arctic Ocean basin over the past three decades. The field observations and results from numerical ocean simulations suggest that this long-term trend toward more oligotrophic (nutrient-poor) conditions is driven primarily by the compound effects of sea-ice loss: a reduced resupply of nutrients from subsurface waters (due to fresh water addition and stronger upper-ocean stratification) coincident with increased biological consumption of nutrients (due to the greater availability of light needed for photosynthesis).

Both remote sensing and numerical models revealed increasing net primary production (NPP) in the Arctic Ocean due to declining sea ice cover and increasing ice-free days. The NPP increases in some parts of the Arctic Ocean are also hypothesized to link to high wind (>10 m/s) and upwelling-favorable wind, however, the mechanism remains unclear. Using Regional Arctic System Model (RASM) to investigate the relationship between NPP and wind, we found that the seasonal NPP are statistically correlated to high wind frequency (HWF) in the Barents (Br) and Southern Chukchi Seas (SC) due to their high subsurface nutrients in the 20-50 m layer. Five high and five low HWF years along a zonally averaged section were chosen to understand the spatial variation of the correlation between HWF, NO 3 , and NPP in the SC. During high HWF years, the decrease in subsurface NO 3 exceeds its increase in surface, implying the utilization by biological productivity. A more positive response of NPP to HWF in north SC than south was also found because more subsurface nutrients were entrained into the surface by higher HWF. The NPP are statistically correlated to easterly wind frequency (EWF) in the Beaufort and Canada Basin (BC), where the stronger EWF-induced upwelling could bring up higher nutrients from >100 m depth. While the nutrients and NPP in the south BC are normally higher than in the north, an increase of EWF can further enhance the nutrients and NPP in the south much more than those in the north. Differences between five high and five low EWF years reveal that the increase of EWF is most important around the shelf break region, where NO 3 and NPP are also most enhanced. The enhancement of NPP by higher HWF in the Br and SC is less than that by higher ice-free days ratio (IFR), while the enhancement of NPP by higher EWF in BC is of similar magnitude to that by IFR. As the trend of declining sea ice cover continues, it’s necessary to advance our understanding on the nutrients and NPP response to changing wind regimes in different Arctic regions.

Amplified Arctic warming has led to a pervasive decline in sea ice cover over recent decades; yet, the pattern and governing mechanisms of sea ice concentration (SIC) state transitions remain unclear. This study reveals pronounced regional contrasts in mean-state SIC during the transition from 1979–2006 to 2007–2024, concurrent with a reduction in the sea ice extent over the same period. The September-mean sea ice in the 70° N–80° N Arctic belt retreated significantly from 1979–2006 to 2007–2024, while the Barents and Greenland Seas exhibited persistent ice loss in March. Enhanced ice-albedo feedback, together with concurrent rises in the 2 m air temperature and sea surface temperature, dominate these ice loss processes. Dynamical processes exert distinct regulatory roles in September and March. The strengthened Beaufort High induces sea ice convergence to partially offset the September thermodynamically driven ice loss, while the positive-phase Arctic Dipole in March amplifies the transpolar airflow and winds over the Greenland and Barents Seas and triggers rapid sea ice export and significant loss in these regions. These findings underscore the spatial heterogeneity of Arctic SIC transitions and highlight the complex interplay of thermodynamic and dynamic processes shaping them.

The SCHISM model is widely used for ocean numerical simulations, but its computational efficiency is constrained by the substantial resources it requires. To enhance its performance, this study develops GPU–SCHISM, a GPU-accelerated parallel version of SCHISM using the CUDA Fortran framework, and this study evaluates its acceleration performance on a single GPU-enabled node. The research results demonstrate that the GPU–SCHISM model achieves computational acceleration while maintaining high simulation accuracy. For small-scale classical experiments, a single GPU improves the efficiency of the Jacobi solver—identified as a performance hotspot—by 3.06 times and accelerates the overall model by 1.18 times. However, increasing the number of GPUs reduces the computational workload per GPU, which hinders further acceleration improvements. The GPU is particularly effective for performing higher-resolution calculations, leveraging its computational power. For large-scale experiments with 2,560,000 grid points, the GPU speedup ratio is 35.13; however, CPU has more advantages in small-scale calculations. Moreover, a comparison between CUDA and OpenACC-based GPU acceleration shows that CUDA outperforms OpenACC under all experimental conditions. This study marks the first successful GPU acceleration of the SCHISM model within the CUDA Fortran framework, laying a preliminary foundation for lightweight GPU-accelerated parallel processing in ocean numerical simulations.

An ice ecosystem model was coupled to a global dynamic sea ice model to assess large‐scale variability of primary production and ice algal biomass within arctic sea ice. The component models are the Physical Ecosystem Model (PhEcoM) ice ecosystem model and the Los Alamos Sea Ice Model (CICE). Simulated annual arctic sea ice primary production was 15.1 Tg C; within the range of 9 to 73 Tg C estimated using in situ data. The amount of C fixed was >3 Tg C month−1 for March, April, and May. The Bering Sea, Arctic Ocean basins, and the Canadian Archipelago/Baffin Bay were the most productive regions on an annual basis, contributing approximately 24, 18, and another 18%, respectively. High production in the Bering Sea was due to high daily production rates, while the large sea ice coverage in the Canadian Archipelago/Baffin Bay and, in particular, the Arctic Ocean basins resulted in their considerable contribution to sea ice primary production. The simulated trends, patterns, and seasonality of ice algae agree reasonably well with very limited observations. In the model, ice growth rate controls the availability of nutrients to sea ice algae, such that ocean nutrient supply is of secondary importance to ice algal growth. The numerical model results suggest that ice melt rate, which determines the proportional rate of ice algal release, controls the termination of the bloom on large scales. The model described advances the role of sea ice algae in biogeochemical cycling within global climate models. Key Points Simulation results are reasonable compared with in situ observations First large‐scale modeling of pan‐Arctic sea ice primary production High annual production is due to either high daily rates or large ice coverage

What are the main findings? * A decadal trend transition in sea surface pCO[sub.2] in the Beaufort Sea was found around 2010–2012 both by observation and via a numerical model. * The sea surface pCO[sub.2] trend transition was driven by a concurrent trend transition in sea ice cover through changing the seasonal duration of open-water. A decadal trend transition in sea surface pCO[sub.2] in the Beaufort Sea was found around 2010–2012 both by observation and via a numerical model. The sea surface pCO[sub.2] trend transition was driven by a concurrent trend transition in sea ice cover through changing the seasonal duration of open-water. What are the implications of the main findings? * This finding improves our understanding of the decadal-scale response of the Arctic Ocean carbon cycle to climate changes. * This finding advances our understanding of the influence of seasonal sea ice variabilities on decadal trends in the carbon cycle. This finding improves our understanding of the decadal-scale response of the Arctic Ocean carbon cycle to climate changes. This finding advances our understanding of the influence of seasonal sea ice variabilities on decadal trends in the carbon cycle. Interannual climate changes and increasing atmospheric CO[sub.2] (AtmCO[sub.2]) have significantly altered sea surface partial pressure of CO[sub.2] (pCO[sub.2]) in the Beaufort Sea (BS). Yet, their decadal variability and underlying mechanisms remain inadequately understood. Using observational data and the Regional Arctic System Model (RASM), a decreasing trend transition of the BS summer surface pCO[sub.2] was identified at around 2010–2012. Sensitivity cases reveal that the decadal trend transition in surface pCO[sub.2] (early: 4.12 ± 0.80 μatm/yr, p < 0.05 and late: 1.23 ± 2.22 μatm/yr, p > 0.05) is driven by interannual climate changes. While the long-term increase in AtmCO[sub.2] does not directly drive surface pCO[sub.2] trend transition, it reduces its magnitude. The sensitivity experiment with no interannual AtmCO[sub.2] changes from 1990 reveals that the statistically significant contributor of the decadal trend transition in surface pCO[sub.2] is the concurrent transition in sea ice concentration (SIC, early: −0.0120 ± 0.0037/yr, p < 0.05 and late: 0.0101 ± 0.0063/yr, p > 0.05). The decadal trend transitions in the subsurface and deep layer pCO[sub.2] are negligible compared to that in the sea surface pCO[sub.2] due to the insignificant influence of interannual climate changes on subsurface and deep layer pCO[sub.2]. The surface pCO[sub.2] decadal trend transition is significantly correlated with a trend transition of CO[sub.2] sink. On seasonal timescales, the effects of SIC on the decadal trend transition of pCO[sub.2] occur primarily within the duration of open-water (DOW), and align with the decadal trend transitions in the open-water start day, end day, and DOW. The magnitude of sea surface pCO[sub.2] trend transition increases as the magnitude of the DOW trend transition increases.