ARTICLE | doi:10.20944/preprints202306.1056.v1
Subject: Environmental And Earth Sciences, Remote Sensing Keywords: mesoscale eddies; chlorophyll concentrations; biogeochemical cycling
Online: 14 June 2023 (14:20:42 CEST)
The Kuroshio Extension(KE) System exhibits highly energetic mesoscale phenomena, but the impact of mesoscale eddies on marine ecosystems and biogeochemical cycling is not well understood. This study utilizes remote sensing and Argo floats to investigate how eddies modify surface and subsurface chlorophyll (Chl-a) concentrations. On average, cyclones (anticyclones) induce positive (negative) surface Chl-a anomalies, particularly in winter. This occurs because cyclones (anticyclones) lift (deepen) isopycnals and nitrate into (out of) the euphotic zone, stimulating (depressing) the growth of phytoplankton. Consequently, cyclones (anticyclones) result in greater (smaller) subsurface Chl-a maximum (SCM), depth-integrated Chl-a, and depth-integrated nitrate. The positive (negative) surface Chl-a anomalies induced by cyclones (anticyclones) are mainly located near (north of) the main axis of the KE. The second and third mode represent monopole Chl-a patterns within eddy centers corresponding to either positive or negative anomalies, depending on the sign of the principal component. Chl-a concentrations in cyclones (anticyclones) above the SCM layer are higher (lower) than the edge values, while those below are lower (higher), regardless of winter variations. The vertical distributions and displacements of Chl-a and SCM depth are associated with eddy pumping. In terms of frequency, negative (positive) Chl-a anomalies account for approximately 26% (18%) of the total cyclones (anticyclones) across all four seasons. The opposite phase suggests that nutrient supply resulting from stratification differences under convective mixing may contribute to negative (positive) Chl-a anomalies in cyclone (anticyclone) cores. Additionally, the opposite phase can also be attributed to eddy stirring, trapping high and low Chl-a, and/or eddy Ekman pumping. Based on OFES outputs, the seasonal variation of nitrate from winter to summer primarily depends on the effect of vertical mixing, indicating that convective mixing processes contribute to an increase (decrease) in nutrients during winter (summer) over the KE.
ARTICLE | doi:10.20944/preprints201806.0200.v1
Subject: Social Sciences, Geography, Planning And Development Keywords: farmland change; soybean; production potential; GAEZ; Western Jilin
Online: 12 June 2018 (16:01:54 CEST)
In recent 40 years, the quantity and spatial patterns of farmland in Western Jilin have changed dramatically, which had great impact on soybean production potential. This study used one of the most advanced crop production potential models, the Global Agro-cological Zones model, to calculate the soybean production potential in Western Jilin based on meteorological, terrain, soil and land use data, and analyzed impact of farmland change on soybean production potential during 1975-2013. The main conclusions were the following. First, the total soybean production potential in Western Jilin in 2013 was 89.22 thousand tons. The production potential of eastern area was higher than the other areas of Western Jilin. Second, farmland change led to a growth of 33.03 thousand tons in soybean production potential between 1975 and 2000, and a decrease of 10.30 thousand tons between 2000 and 2013. Third, taking account of two situations of farmland change, the conversion between dryland and other categories, and the change of irrigation percentage led to the total soybean production potential in Western Jilin increased by 23.13 and only 2.87 thousand tons respectively between 1975 and 2000, and increased by 1.13 and 2.81 thousand tons respectively between 2000 and 2013. In general, the increase of soybean potential production was mainly due to grassland and woodland reclamation. The results of this study would be a good reference for protecting safe baseline of farmland, managing land resources, and ensuring continuity and stability of soybean supply and food security.