Skip to main content

LUP Student Papers

LUND UNIVERSITY LIBRARIES

Impact Assessment of Extreme Freshwater Inflow on the Formation and Dissipation of Hypoxia in the Ariake Sea Using Large Ensemble Climate Simulation Database

Sanada, Ai LU (2026) In TVVR 5000 VVRM01 20252
Division of Water Resources Engineering
Abstract
It is apparent that climate change is progressing, increasing the frequency of
heavy rainfall events. In coastal areas, halocline formation caused by increased
freshwater inflow can inhibit vertical mixing, reducing oxygen concentration
in the bottom layer. The Ariake Sea, an inner bay in Japan with a large tidal
range, has faced serious issues such as red tides and hypoxia. Previous studies
have revealed that increased river discharge can prolong hypoxia duration in
the bay. For instance, the longest hypoxic event was observed during the 2020
flood. This study investigates how extreme freshwater inflow influences
hypoxia dynamics using a large ensemble climate simulation database
including both present and future... (More)
It is apparent that climate change is progressing, increasing the frequency of
heavy rainfall events. In coastal areas, halocline formation caused by increased
freshwater inflow can inhibit vertical mixing, reducing oxygen concentration
in the bottom layer. The Ariake Sea, an inner bay in Japan with a large tidal
range, has faced serious issues such as red tides and hypoxia. Previous studies
have revealed that increased river discharge can prolong hypoxia duration in
the bay. For instance, the longest hypoxic event was observed during the 2020
flood. This study investigates how extreme freshwater inflow influences
hypoxia dynamics using a large ensemble climate simulation database
including both present and future scenarios. Results indicate that the influence
of discharge weakens under extremely severe flood events. Although
freshwater volume strongly correlates with stratification intensity, hypoxia
duration does not exhibit a clear relationship with discharge. Qualitative
analyses based on time series data and vertical profiles suggest that hypoxia
formation is mainly controlled by discharge-driven stratification, whereas its
dissipation depends on subsequent disturbances such as strong winds and
spring tides. These differing controls can increase the uncertainty and
variability of hypoxia duration under extreme conditions and in future climate
projections. (Less)
Popular Abstract
It is apparent that climate change is progressing, increasing the frequency of
heavy rainfall events. In coastal areas, halocline formation caused by increased
freshwater inflow can inhibit vertical mixing, reducing oxygen concentration
in the bottom layer. The Ariake Sea, an inner bay in Japan with a large tidal
range, has faced serious issues such as red tides and hypoxia. Previous studies
have revealed that increased river discharge can prolong hypoxia duration in
the bay. For instance, the longest hypoxic event was observed during the 2020
flood. This study investigates how extreme freshwater inflow influences
hypoxia dynamics using a large ensemble climate simulation database
including both present and future... (More)
It is apparent that climate change is progressing, increasing the frequency of
heavy rainfall events. In coastal areas, halocline formation caused by increased
freshwater inflow can inhibit vertical mixing, reducing oxygen concentration
in the bottom layer. The Ariake Sea, an inner bay in Japan with a large tidal
range, has faced serious issues such as red tides and hypoxia. Previous studies
have revealed that increased river discharge can prolong hypoxia duration in
the bay. For instance, the longest hypoxic event was observed during the 2020
flood. This study investigates how extreme freshwater inflow influences
hypoxia dynamics using a large ensemble climate simulation database
including both present and future scenarios. Results indicate that the influence
of discharge weakens under extremely severe flood events. Although
freshwater volume strongly correlates with stratification intensity, hypoxia
duration does not exhibit a clear relationship with discharge. Qualitative
analyses based on time series data and vertical profiles suggest that hypoxia
formation is mainly controlled by discharge-driven stratification, whereas its
dissipation depends on subsequent disturbances such as strong winds and
spring tides. These differing controls can increase the uncertainty and
variability of hypoxia duration under extreme conditions and in future climate
projections. (Less)
Please use this url to cite or link to this publication:
author
Sanada, Ai LU
supervisor
organization
course
VVRM01 20252
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Climate change, Hypoxia, the Ariake Sea, Large ensemble climate simulation database, Coastal environment
publication/series
TVVR 5000
report number
TVVR-25/5018
ISSN
1101-9824
language
English
additional info
Examine; Ronny Berndtsson
id
9223777
date added to LUP
2026-03-09 13:48:46
date last changed
2026-03-09 13:48:46
@misc{9223777,
  abstract     = {{It is apparent that climate change is progressing, increasing the frequency of 
heavy rainfall events. In coastal areas, halocline formation caused by increased 
freshwater inflow can inhibit vertical mixing, reducing oxygen concentration 
in the bottom layer. The Ariake Sea, an inner bay in Japan with a large tidal 
range, has faced serious issues such as red tides and hypoxia. Previous studies 
have revealed that increased river discharge can prolong hypoxia duration in 
the bay. For instance, the longest hypoxic event was observed during the 2020 
flood. This study investigates how extreme freshwater inflow influences 
hypoxia dynamics using a large ensemble climate simulation database 
including both present and future scenarios. Results indicate that the influence 
of discharge weakens under extremely severe flood events. Although 
freshwater volume strongly correlates with stratification intensity, hypoxia 
duration does not exhibit a clear relationship with discharge. Qualitative 
analyses based on time series data and vertical profiles suggest that hypoxia 
formation is mainly controlled by discharge-driven stratification, whereas its 
dissipation depends on subsequent disturbances such as strong winds and 
spring tides. These differing controls can increase the uncertainty and 
variability of hypoxia duration under extreme conditions and in future climate 
projections.}},
  author       = {{Sanada, Ai}},
  issn         = {{1101-9824}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{TVVR 5000}},
  title        = {{Impact Assessment of Extreme Freshwater Inflow on the Formation and Dissipation of Hypoxia in the Ariake Sea Using Large Ensemble Climate Simulation Database}},
  year         = {{2026}},
}