Arctic sea level data from tidal gauge and model simulations from 1948-2009@en

A suite of model simulations is used to investigate the spatiotemporal variability of the Arctic Ocean circulation and the observing systems required to capture it. A comparison with sea level observations shows that all model runs realistically simulate inter-annual sea level varia-bility, but the simulated seasonal sea level variability and underlying changes in the model salinity need to be further improved. At periods <30 days, sea level variability is equivalent barotropic and strongly captured by bottom pressure observations. At the seasonal period, both barotropic and baroclinic processes contribute involving variations in the mass and densi-ty fields. Over the entire Arctic Ocean, steric height variability is dominated by halosteric effects in the upper layer. The salinity changes are related to sea ice processes, river runoff, and redistribution of the freshwater. At decadal timescales, sea level variations in the Canadi-an Basin relate to halosteric effects in the upper and intermediate layers. An adjoint sensitivi-ty analysis reveals that the decadal salinity variability is caused by anticyclonic/cyclonic wind stress, which accumulate/release freshwater in the upper layer and enhance/reduce geostrophic currents in the intermediate layer. The adjoint model simulations identify the importance of moorings and satellite altimetry on monitoring the Arctic salinity and circulation changes: while moorings capture more local salinity changes, the satellite altimetry may capture the influence of freshwater originating from the Bering Strait and the Eurasian Basin. Our study suggests that to capture basin-wide salinity changes, we need to deploy moorings in different positions spreading across the Arctic Ocean.本研究依托多组模式模拟实验，探究北冰洋环流的时空变率，以及捕捉该变率所需的观测系统配置方案。通过与海平面观测资料的对比分析可知，所有模式模拟结果均能较为真实地复现海平面年际变率，但模拟得到的季节尺度海平面变率，以及模式中盐度的相关演变过程仍有待进一步改进与完善。在周期短于30天的时段内，海平面变率呈等价正压（equivalent barotropic）特征，且可通过海底压力观测资料有效捕捉。在季节尺度上，正压与斜压过程共同作用，涉及质量场与密度场的变化。在整个北冰洋海域，比容海平面高度（steric height）变率主要受上层海水的盐比容效应（halosteric effects）支配。盐度变化与海冰过程、河流径流以及淡水的再分配密切相关。在年代际尺度上，加拿大海盆（Canadian Basin）的海平面变化与上层及中层海水的盐比容效应相关。伴随敏感性分析（adjoint sensitivity analysis）结果表明，年代际尺度的盐度变率由反气旋式/气旋式风应力驱动：此类风应力会在上层海水蓄积/释放淡水，并增强/减弱中层海水的地转流（geostrophic currents）。伴随模式模拟结果揭示了锚系观测浮标（moorings）与卫星测高（satellite altimetry）在监测北极盐度与环流变化中的重要性：锚系浮标可更精准捕捉局地盐度变化，而卫星测高则能监测源自白令海峡（Bering Strait）与欧亚海盆（Eurasian Basin）的淡水影响。本研究建议，若要捕捉全海盆尺度的盐度变化，需在北冰洋全域的不同位置布设锚系观测浮标。