Observed variability of monsoon blooms in the north-central Arabian Sea and its implication on oxygen concentration: A Bio-Argo study

Mapping Intimacies ◽

10.5194/egusphere-egu21-16286 ◽

2021 ◽

Author(s):

Teesha Mathew

Keyword(s):

Arabian Sea ◽

Chlorophyll Concentration ◽

Physical Processes ◽

Study Region ◽

North Central ◽

Argo Float ◽

The North ◽

Surface Productivity ◽

Do Concentration ◽

Summer Bloom

The central Arabian Sea (CAS) is productive during both the summer and winter monsoons owing to different physical processes. We analysed four years (2013-2016) record of chlorophyll and dissolved oxygen (DO) concentration from a Bio-Argo float deployed in this region. Though the surface blooms were observed during both the monsoons and sub-surface chlorophyll was also persistently observed, the intensity and duration of the bloom have been decreasing over the past few years. Also, the winter blooms were more prominent compared to the summer bloom in the study region. Our analysis shows that the observed inter-annual variability in the summer bloom can be attributed to the variability in wind speed, oceanic stratification and advection of nutrient rich water from the western Arabian Sea. During both the monsoons, stratification played an important role in reducing the productivity in recent years. We also found that during the winter monsoon, the upwelling Rossby wave propagating from the west coast of India influenced productivity as north as 15&#186;N. The chlorophyll data from Bio-Argo float shows that the total surface chlorophyll concentration has been decreasing during the study period. Consequently the DO concentration has also been decreased. An increase in the deeper water is speculated to be due to the decrease in surface productivity. This is in contradiction to the previous studies on intensification of Arabian Sea OMZ. Also, in the event of recent reports on decreasing trend in productivity in the Arabian Sea, the present study provides new insights on the possible effect of declining productivity on the DO concentration under the climate change regime.

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Carbon Flux of Down Woody Materials in Forests of the North Central United States

International Journal of Forestry Research ◽

10.1155/2010/413703 ◽

2010 ◽

Vol 2010 ◽

pp. 1-9 ◽

Cited By ~ 13

Author(s):

C. W. Woodall

Keyword(s):

United States ◽

Forest Inventory ◽

Woody Debris ◽

Stand Age ◽

Future Research ◽

Study Region ◽

North Central ◽

The North ◽

C Stocks ◽

Central United States

Across large scales, the carbon (C) flux of down woody material (DWM) detrital pools has largely been simulated based on forest stand attributes (e.g., stand age and forest type). The annual change in forest DWM C stocks and other attributes (e.g., size and decay class changes) was assessed using a forest inventory in the north central United States to provide an empirical assessment of strategic-scale DWM C flux. Using DWM inventory data from the USDA Forest Service's Forest Inventory and Analysis program, DWM C stocks were found to be relatively static across the study region with an annual flux rate not statistically different from zero. Mean C flux rates across the study area were 0.25, 0.12, 0.01, and 0.04 (Mg/ha/yr) for standing live trees, standing dead trees, coarse woody debris, and fine woody debris, respectively. Flux rates varied in their both magnitude and status (emission/sequestration) by forest types, latitude, and DWM component size. Given the complex dynamics of DWM C flux, early implementation of inventory remeasurement, and relatively low sample size, numerous future research directions are suggested.

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Evaluation of Reanalyzed Precipitation Variability and Trends Using the Gridded Gauge-Based Analysis over the CONUS

Journal of Hydrometeorology ◽

10.1175/jhm-d-17-0029.1 ◽

2017 ◽

Vol 18 (8) ◽

pp. 2227-2248 ◽

Cited By ~ 6

Author(s):

Wenjun Cui ◽

Xiquan Dong ◽

Baike Xi ◽

Aaron Kennedy

Keyword(s):

Complex Terrain ◽

Systematic Errors ◽

Precipitation Variability ◽

Physical Processes ◽

North Central ◽

The North ◽

Spatial Trends ◽

Precipitation Estimates ◽

Global Coverage ◽

Regional Reanalysis

Abstract Atmospheric reanalyses have been used in many studies to investigate the variabilities and trends of precipitation because of their global coverage and long record; however, their results must be properly analyzed and their uncertainties must be understood. In this study, precipitation estimates from five global reanalyses [ERA-Interim; MERRA, version 2 (MERRA2); JRA-55; CFSR; and 20CR, version 2c (20CRv2c)] and one regional reanalysis (NARR) are compared against the CPC Unified Gauge-Based Analysis (CPCUGA) and GPCP over the contiguous United States (CONUS) during the period 1980–2013. Reanalyses capture the variability of the precipitation distribution over the CONUS as observed in CPCUGA and GPCP, but large regional and seasonal differences exist. Compared with CPCUGA, global reanalyses generally overestimate the precipitation over the western part of the country throughout the year and over the northeastern CONUS during the fall and winter seasons. These issues may be associated with the difficulties models have in accurately simulating precipitation over complex terrain and during snowfall events. Furthermore, systematic errors found in five global reanalyses suggest that their physical processes in modeling precipitation need to be improved. Even though negative biases exist in NARR, its spatial variability is similar to both CPCUGA and GPCP; this is anticipated because it assimilates observed precipitation, unlike the global reanalyses. Based on CPCUGA, there is an average decreasing trend of −1.38 mm yr−1 over the CONUS, which varies depending on the region with only the north-central to northeastern parts of the country having positive trends. Although all reanalyses exhibit similar interannual variation as observed in CPCUGA, their estimated precipitation trends, both linear and spatial trends, are distinct from CPCUGA.

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