Recent trends in air-sea CO2 fluxes and ocean acidification in the Arabian Sea

2021 ◽  
Author(s):  
Zouhair Lachkar ◽  
Michael Mehari ◽  
Alain De Verneil ◽  
Marina Lévy ◽  
Shafer Smith
Keyword(s):  
Ocean Acidification ◽  
Arabian Sea ◽  
Coastal Upwelling ◽  
Biogeochemical Model ◽  
Atmospheric Concentration ◽  
Physical Forcing ◽  
Freshwater Fluxes ◽  
Ocean Biogeochemical Model ◽  
Long Term Trends

<p>Recent observations and modeling evidence indicate that the Arabian Sea (AS) is a net source of carbon to the atmosphere. Yet, the interannual variability modulating the air-sea CO<sub>2</sub> fluxes in the region, as well as their long-term trends, remain poorly known. Furthermore, while the rising atmospheric concentration of CO<sub>2</sub> is causing surface ocean pH to drop globally, little is known about local and regional acidification trends in the AS, a region hosting a major coastal upwelling system naturally prone to relatively low surface pH. Here, we simulate the evolution of air-sea CO<sub>2</sub> fluxes and reconstruct the progression of ocean acidification in the AS from 1982 through 2019 using an eddy-resolving ocean biogeochemical model covering the full Indian Ocean and forced with observation-based winds and heat and freshwater fluxes. Additionally, using a set of sensitivity simulations that vary in terms of atmospheric CO<sub>2</sub> levels and physical forcing we quantify the variability of fluxes associated with both natural and anthropogenic CO<sub>2</sub> and disentangle the contributions of climate variability and that of atmospheric CO<sub>2</sub> concentrations to the long-term trends in air-sea CO<sub>2</sub> fluxes and acidification. Our analysis reveals a strong variability in the air-sea CO<sub>2</sub> fluxes and pH on a multitude of timescales ranging from the intra-seasonal to the decadal. Furthermore, a strong progression of ocean acidification with an important penetration into the thermocline is simulated locally near the upwelling regions. Our analysis also indicates that in addition to the increasing anthropogenic CO<sub>2</sub> concentrations in the atmosphere, recent warming and monsoon wind changes have substantially modulated these trends regionally.</p>

scholarly journals PISCES-v2: an ocean biogeochemical model for carbon and ecosystem studies

2015 ◽  
Vol 8 (2) ◽  
pp. 1375-1509 ◽  
Author(s):  
O. Aumont ◽  
C. Ethé ◽  
A. Tagliabue ◽  
L. Bopp ◽  
M. Gehlen
Keyword(s):  
Growth Rate ◽  
Marine Ecosystem ◽  
Trophic Levels ◽  
Full Description ◽  
Biogeochemical Model ◽  
Ecosystem Studies ◽  
Ocean Biogeochemical Model ◽  
Iron Chemistry ◽  
Steady State Simulation

Abstract. PISCES-v2 is a biogeochemical model which simulates the lower trophic levels of marine ecosystem (phytoplankton, microzooplankton and mesozooplankton) and the biogeochemical cycles of carbon and of the main nutrients (P, N, Fe, and Si). The model is intended to be used for both regional and global configurations at high or low spatial resolutions as well as for short-term (seasonal, interannual) and long-term (climate change, paleoceanography) analyses. There are twenty-four prognostic variables (tracers) including two phytoplankton compartments (diatoms and nanophytoplankton), two zooplankton size-classes (microzooplankton and mesozooplankton) and a description of the carbonate chemistry. Formulations in PISCES-v2 are based on a mixed Monod–Quota formalism: on one hand, stoichiometry of C/N/P is fixed and growth rate of phytoplankton is limited by the external availability in N, P and Si. On the other hand, the iron and silicium quotas are variable and growth rate of phytoplankton is limited by the internal availability in Fe. Various parameterizations can be activated in PISCES-v2, setting for instance the complexity of iron chemistry or the description of particulate organic materials. So far, PISCES-v2 has been coupled to the NEMO and ROMS systems. A full description of PISCES-v2 and of its optional functionalities is provided here. The results of a quasi-steady state simulation are presented and evaluated against diverse observational and satellite-derived data. Finally, some of the new functionalities of PISCES-v2 are tested in a series of sensitivity experiments.

scholarly journals Long-term variations in ocean acidification indices in the Northwest Pacific from 1993 to 2018

2021 ◽  
Vol 168 (3-4) ◽  
Author(s):  
Miho Ishizu ◽  
Yasumasa Miyazawa ◽  
Xinyu Guo
Keyword(s):  
Ocean Acidification ◽  
Observational Data ◽  
Dissolved Inorganic Carbon ◽  
Carbon Sink ◽  
Kuroshio Extension ◽  
Biogeochemical Model ◽  
Northwest Pacific ◽  
Subarctic Region ◽  
Long Term Variations

AbstractLong-term variations in ocean acidification indices in the Northwest Pacific were examined using observational data and a biogeochemical model with an operational ocean model product for the period 1993–2018. The model and observational data for the surface ocean (< 100-m depth) exhibit consistent patterns of ocean acidification in the subtropical and Kuroshio Extension regions and relative alkalinization (i.e., reduced acidification) in the subarctic region of the Northwest Pacific. Below 100-m depth, acidification dominated in the subtropical regions and alkalinization in the subarctic regions. We attribute the excess acidification in the subtropical and Kuroshio regions to the vertical mixing of dissolved inorganic carbon (DIC) exceeding the DIC release by air–sea exchange. These regional differences in acidification and alkalinization are attributed to spatially variable biological processes in the upper ocean and horizontal and vertical physical redistribution of DIC. Our model and observational results have implications for the spatial extent and pattern of ocean acidification, along with the strength of the ocean carbon sink, which are key aspects of global climate change.

scholarly journals Long term trends in the frequency of monsoonal cyclonic disturbances over the north Indian Ocean

MAUSAM ◽  
2022 ◽  
Vol 52 (4) ◽  
pp. 655-658
Author(s):  
O. P. SINGH
Keyword(s):  
Arabian Sea ◽  
Monsoon Season ◽  
Southwest Monsoon ◽  
North Indian Ocean ◽  
The North ◽  
Long Term Trends ◽  
Cyclonic Disturbances ◽  
Southwest Monsoon Season ◽  
Cyclonic Storms

Long term trends in the frequencies of cyclonic disturbances (i.e. depressions and cyclonic storms) and the cyclonic storms forming over the Bay of Bengal and the Arabian Sea during the southwest monsoon season (June-September) have been studied utilizing 110 years data from 1890-1999. There have been significant decreasing trends in both the frequencies but the frequency of cyclonic disturbances has diminished at a faster rate. The trend analysis shows that the frequency of cyclonic disturbances has decreased at the rate of about six to seven disturbances per hundred years in the monsoon season. The frequency of cyclonic storms of monsoon season .has decreased at the rate of , one to two cyclones per hundred years.

scholarly journals On the role of ozone in long-term trends in the upper atmosphere-ionosphere system

2012 ◽  
Vol 30 (5) ◽  
pp. 811-816 ◽  
Author(s):  
J. Laštovička
Keyword(s):  
Ozone Depletion ◽  
Stratospheric Ozone ◽  
Lower Thermosphere ◽  
Main Magnetic Field ◽  
Atmospheric Concentration ◽  
Limited Region ◽  
Long Term Trends ◽  
Mesosphere And Lower Thermosphere

Abstract. Origin of long-term trends in the thermosphere-ionosphere system has been discussed since the beginning of trend studies. The two most prioritized explanations have been those via long-term increase of atmospheric concentration of greenhouse gases and long-term increase of geomagnetic activity throughout the 20th century. Secular changes of the Earth's main magnetic field play an important role in trends in a limited region. Recently, Walsh and Oliver (2011) suggested that the long-term cooling of the upper thermosphere (above 200 km) may be due largely to the stratospheric ozone depletion. Here, we show that the role of ozone is very important in the mesosphere and lower thermosphere but not in the upper thermosphere. The suggestion of Walsh and Oliver (2011) is based on historical (before 1988) data from Saint-Santin radar, whereas more recent data do not support their conclusion.

scholarly journals Long-term trends in the middle atmosphere dynamics at northern middle latitudes – one regime or two different regimes?

2010 ◽  
Vol 10 (2) ◽  
pp. 2633-2668 ◽  
Author(s):  
J. Lastovicka ◽  
P. Krizan ◽  
M. Kozubek
Keyword(s):  
Middle Atmosphere ◽  
Stratospheric Ozone ◽  
Atmospheric Concentration ◽  
Mesopause Region ◽  
Middle Latitudes ◽  
Middle Atmosphere Dynamics ◽  
E Region ◽  
Long Term Trends ◽  
Middle Atmospheric Dynamics

Abstract. Due to increasing atmospheric concentration of greenhouse gases and changing stratospheric ozone concentration, both of anthropogenic origin, various quantities in the middle atmosphere reveal long-term changes and trends. Lastovicka and Krizan (2006) indicated possibility of change of trends in the dynamics in the northern midlatitude middle atmosphere as a whole in the 1990s. To search for such change of trends we use data on winds in the mesopause region, on total columnar ozone, on ozone laminae, on winds in the middle and lower stratosphere, and on peak electron density in the E region of the ionosphere. One group of quantities, the mesopause region wind-like trends, changes their trends around 1990, the other one, the total ozone-like trends, in the mid-1990s. Altogether they create a skeleton of scenario of the change of the middle atmosphere dynamics trends in the 1990s. Drivers of these changes appear to be different for the first group and for the second group. Tropospheric processes seem to play a role in the changes of trends in middle atmospheric dynamics.

scholarly journals The relationship between Arabian Sea upwelling and Indian monsoon revisited

2015 ◽  
Vol 12 (6) ◽  
pp. 2683-2704 ◽  
Author(s):  
X. Yi ◽  
B. Hünicke ◽  
N. Tim ◽  
E. Zorita
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Arabian Sea ◽  
Coastal Upwelling ◽  
Sea Surface ◽  
Global Ocean ◽  
Western Coast ◽  
Very High Spatial Resolution ◽  
Arabian Sea Upwelling

Abstract. Studies based on upwelling indices (sediment records, sea-surface temperature and wind) suggest that upwelling along the western coast of Arabian Sea is strongly affected by the Indian summer monsoon (ISM). In order to examine this relationship directly, we employ the vertical water mass transport produced by the eddy-resolving global ocean simulation STORM driven by meteorological reanalysis over the last 61 years. With its very high spatial resolution (10 km), STORM allows us to identify characteristics of the upwelling system. We analyze the co-variability between upwelling and meteorological and oceanic variables from 1950 to 2010. The analyses reveal high interannual correlations between coastal upwelling and along-shore wind-stress (r=0.73) as well as with sea-surface temperature (r0.83). However, the correlation between the upwelling and the ISM is small and other factors might contribute to the upwelling variability. In addition, no long-term trend is detected in our modeled upwelling time series.

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