Model derived uncertainties in deep ocean temperature trends between 1990-2010 (dataset)

We construct a novel framework to investigate the uncertainties and biases associated with estimates of deep ocean temperature change from hydrographic sections, and demonstrate this framework in an eddy-permitting ocean model. Biases in estimates from observations arise due to sparse spatial coverage (few sections in a basin), low frequency of occupations (typically 5-10 years apart), mismatches between the time period of interest and span of occupations, and from seasonal biases relating to the practicalities of sampling during certain times of year. Between the years 1990 and 2010, the modeled global abyssal ocean biases are small, although regionally some biases (expressed as a heat flux into the 4000 - 6000 m layer) can be up to 0.05 W/m². In this model, biases in the heat flux into the deep 2000 - 4000 m layer, due to either temporal or spatial sampling uncertainties, are typically much larger and can be over 0.1 W/m² across an ocean. Overall, 82% of the warming trend deeper than 2000 m is captured by hydrographic section-style sampling in the model. At 2000 m, only half the model global warming trend is obtained from observational-style sampling, with large biases in the Atlantic, Southern and Indian Oceans. Biases due to different sources of uncertainty can have opposing signs and differ in relative importance both regionally and with depth, revealing the importance of reducing temporal and spatial uncertainties in future deep ocean observing design.

本研究构建了一套新颖的框架，用于探究基于水文断面（hydrographic sections）估算深海温度变化时所伴随的不确定性与偏差，并在涡容许海洋模式（eddy-permitting ocean model）中验证了该框架的适用性。
基于观测的估算结果之所以存在偏差，原因包括空间覆盖稀疏（单个海盆内的水文断面数量极少）、复测频次偏低（通常间隔5至10年）、目标研究时段与复测时段不匹配，以及与特定季节采样作业实际情况相关的季节偏差。
在1990年至2010年间，模式模拟的全球深渊海洋偏差整体较小，但部分区域的偏差（以注入4000~6000米水层的热通量计）最高可达0.05 W/m²。
在该模式中，因时间或空间采样不确定性导致的、注入2000~4000米深层水层的热通量偏差通常显著更大，在整个大洋范围内可超过0.1 W/m²。
整体而言，该模式中，水文断面式采样可捕捉到2000米以深海域82%的增温趋势。
在2000米深度处，基于观测式采样仅能获取该模式中全球一半的增温趋势，大西洋、南大洋与印度洋均存在较大偏差。
不同不确定性来源带来的偏差可能符号相反，且其相对重要性随区域与深度而异，这凸显了在未来深海观测系统设计中降低时间与空间采样不确定性的重要性。