Modelled seabed response to possible climate change scenarios over the next 50 years in the Australian North - Stationary scenario datasets with Sedsim input files and output files

Using data from ocean forecast models, field observations and seabed sampling we ran a numerical sediment transport model to estimate the Australian Shelf seabed evolution under three climate change scenarios. This data collection is for the Stationary climate change scenario in which the present climate continues for next 50 years.\n\nIn this study, the interaction of seabed sediment types and hydrodynamic forces in the northern region has been investigated using a state-of-the-art numerical model, Sedsim. The simulation area for this collection covers the Gulf of Carpentaria (GOC), the Torres Strait, north-western part of Coral Sea and the eastern part of Arafura Sea.\n\nThe model uses the known grain-size distribution of the present-day seabed based on a comprehensive analysis of currently available seabed data Information available from this data source includes grainsize, mud content, rock exposure, and estimates of critical seabed shear stress. This sediment layer is incorporated in the latest high-resolution (0.0025°) seabed bathymetry obtained from the Australian National Oceans Office (NOO). The seabed topography and present-day sediment layer are represented by a 566 (columns) by 550 (rows) grid with a spatial resolution of 2.1 km. The environmental forcing factors considered in the present model are sediment-laden river flows and turbidity currents, waves, tides, wind-driven currents, sea level change, submarine slope failure and carbonate sediment production.\nLineage: Long-term seabed change is the cumulative result of dynamic forcing and sediment responses. The environmental forces integrated in the model are:\n sediment-laden river flows,\n temperature and salinity variations,\n waves and tides regimes,\n wind-driven currents,\n ocean geostrophic currents,\n sea-level changes,\n submarine slope failures and turbidity currents.\n\nThe Defence Oceanographic Data Centre has provided the wind climate in a monthly form. The data consist of mean and maximum wind speed and simultaneous wind direction when maximum speed occurred. The original wind data cover the time period from July 1999 to May 2004 at a resolution of 0.25°.\nCSIRO WAM wave model has been used to define wave condition around the Australian Shelf. The data are six-hourly predictions of significant wave height, period and mean wave direction, gridded at 0.1° spatial resolution, for the period of March 1997 to February 2002.\nThe National Tidal Centre has provided the tidal range and depth-averaged tidal current speed (5 minutes resolution). In addition, bottom current fields simulated by the Ocean Forecasting Australia Model (0.1° spatial resolution) are used as input into the sediment-transport model. High-frequency water movement caused by wave and tides are the major factors affecting the seabed sediment availability to long-term and large scale transport although the net sediment movement by waves and tides may be negligible, at least in deep water.\nIn the model, seabed mobility index (ratio between the total and critical Shields parameter (induced by wave, tidal current and wind-driven current)) serves as the major indicator of the level of intensity and frequency of seabed sediment available for movement. Modification of the mobility index formulation integrates effects of reef, algae and mangroves on sediment transport and mobility. The mobility index is calculated under the condition of monthly mean and extreme climate.\nThe Australian Shelf has been divided in nine regions. This data collection is for the North region. Depending on the area, several meshes have been used with cell size ranging between 2000 and 2400 metres. The construction of an existing seabed deposit layer is mainly based on the comprehensive sediment database auSEABED. The data collected are mostly retrieved from grabbed samples and bottom photographs. Based on this compilation the mean sediment grain size, the rock membership, the gravel and carbonates content have been estimated. Very little data is available to determine the thickness of loose sediment. The main reason being that the thinness of the sediment veneer covering the hard ground makes gravity coring almost impossible. Thus initial seabed loose sediment thickness is built on available data and according to simple rules for depth and rock membership.\nFor the Australian Shelf simulation, 131 major river and inlet systems have been identified and evaluated in terms of their annual sediment carrying capacity. Mean annual river discharge and sediment yield have been mainly extracted from the OzEstuaries database and converted into discharge rates and sediment concentration.

本研究依托海洋预报模式、现场观测与海底采样数据，运行数值泥沙输运模型（numerical sediment transport model），以估算三种气候变化情景下澳大利亚陆架（Australian Shelf）的海底演化过程。本次数据集对应其中的静止气候变化情景（Stationary climate change scenario），即未来50年维持当前气候状态。

本研究采用当前领先的数值模型Sedsim，对北部海域的海底沉积物类型与水动力作用力的相互作用展开了调研。本次数据集的模拟区域涵盖卡奔塔利亚湾（Gulf of Carpentaria, GOC）、托雷斯海峡（Torres Strait）、珊瑚海（Coral Sea）西北海域与阿拉弗拉海（Arafura Sea）东部海域。

模型基于对现有海底数据的全面分析，采用当前海底沉积物的已知粒度分布。本数据集提供的信息包括沉积物粒度、泥质含量（mud content）、岩石裸露率，以及临界海底剪切应力估算值。该沉积物层整合自澳大利亚国家海洋局（Australian National Oceans Office, NOO）发布的最新高分辨率（0.0025°）海底水深地形数据。研究采用566列×550行的网格来表征海底地形与当前海底沉积物层，空间分辨率为2.1 km。本模型考虑的环境强迫因子包括：挟沙径流、浊流、波浪、潮汐、风生流、海平面变化、海底斜坡失稳与碳酸盐沉积物生成。

数据集谱系：长期海底变化是动力强迫与沉积物响应的累积结果。模型整合的环境作用力包括：
1. 挟沙径流
2. 温度与盐度变化
3. 波浪与潮汐系统
4. 风生流
5. 海洋地转流
6. 海平面变化
7. 海底斜坡失稳与浊流

国防海洋数据中心（Defence Oceanographic Data Centre）提供了逐月的风气候数据，包含平均风速、最大风速，以及最大风速出现时的同步风向。原始风数据的时间跨度为1999年7月至2004年5月，空间分辨率为0.25°。

采用CSIRO WAM波浪模型（CSIRO WAM wave model）来定义澳大利亚陆架周边的波浪条件，数据为1997年3月至2002年2月期间的每6小时预报结果，包含有效波高、周期与平均波浪方向，空间网格分辨率为0.1°。

国家潮汐中心（National Tidal Centre）提供了潮差与深度平均潮流速度（时间分辨率为5分钟）。此外，由澳大利亚海洋预报模型（Ocean Forecasting Australia Model）模拟的底层流场（空间分辨率0.1°）被用作泥沙输运模型的输入数据。尽管波浪与潮汐引发的净泥沙输运在深水海域可忽略不计，但由波浪与潮汐引发的高频水体运动是影响海底沉积物可获取性以支持长期、大规模输运的核心因素。

在模型中，海底活动性指数（总希尔兹参数与临界希尔兹参数的比值，后者由波浪、潮流与风生流诱导产生）被用作衡量可移动海底沉积物强度与频率的核心指标。本活动性指数的公式修正整合了珊瑚礁、藻类与红树林对泥沙输运与活动性的影响。该指数基于月均与极端气候条件进行计算。

澳大利亚陆架被划分为9个区域，本次数据集对应北部区域。根据区域差异，本次模拟采用了多个网格单元，单元尺寸介于2000至2400米之间。现有海底沉积层的构建主要基于auSEABED综合沉积物数据库。收集的数据主要取自抓斗采样与海底照片。基于该汇编数据，研究估算了平均沉积物粒度、岩石占比、砾石与碳酸盐含量。目前可用于估算松散沉积物厚度的数据极少，主要原因是覆盖硬质基底的沉积物盖层过薄，使得重力岩心采样几乎无法实施。因此，初始海底松散沉积物厚度基于现有数据，并结合水深与岩石占比的简单规则进行构建。

针对澳大利亚陆架的模拟，研究识别并评估了131条主要河流与河口系统的年输沙能力。年均径流量与产沙量主要取自OzEstuaries数据库，并转换为径流量与泥沙浓度。