Sediment discharge time series
The challenge set by DG-mare for this project is to create a time series of the total sediment output of rivers into the Arctic Ocean. In order to fulfill this goal an inventory of existing data sets is made. New scientific work to create an assessment of this parameter is not part of the project of challenge. Therefore we will not calculate sediment transport assessment from .e.g. river discharges.
Databases of (total) sediment discharge measurements for the Pan-Arctic region have not been identified. Only suspended sediment concentration (SSC) measurements have been found for individual rivers. These SSC measurements are however usually intermittent and only available for some rivers. Furthermore only knowing the SSC is insufficient to estimate the total sediment discharge since the bed load sediment discharge to the Arctic Ocean remains unobserved. The suspended load is often the largest part of the total sediment load. Turowski et al. 2010 report on the ratio of suspended to bed load and find that extrapolation of the total load based on the suspended load is inaccurate.
These SSC measurements can provide a basis to estimate the total suspended sediment discharge to the Arctic Ocean. However, currently considerable extrapolation of data is needed to provide this estimate. The sediment discharge is delivered by a few large rivers, and many small rivers. Many of these small rivers flow from glaciated terrain into the ocean and most are unmonitored. A problem in the estimation of the total sediment discharge is that the many small streams may carry significant sediment loads, while at the same time their load is highly irregular and the rating curve are very specific for particular streams. Observation of the sediment discharge from the many small streams therefore requires an enormous monitoring effort. A notable example of a well monitored small stream is the Zackenberg River in Northeast Greenland (Ladegaard-Pedersen et al., 2016) here short, but very detailed time series of SSC has been measured.
The few large arctic rivers exhibit relatively slow changes in the sediment concentration, therefore the monitoring is more feasible, but still very expensive in practice. This explains the scarce measurements on the SSC. The SSC datasets that have been identified are the SSC datasets in HYDAT, the USGS database for the Yukon starting in 1976 and the Arctic-GRO dataset for the 6 largest Arctic Rivers, starting in 2003.
As mentioned before a measured datasets that allows the determination of the timeseries of the yearly total sediment discharge into the Arctic Ocean has not been found. The best assessment of the average yearly sediment output of rivers into the Arctic Ocean probably comes from Overeem and Syvitsky (2008) who use discharge information to model the sediment output. Furthermore, the FAO-Aquastat database contains average sediment yields for catchments worldwide, among which many Arctic Catchments. It doesn’t contain time series however and it is not updated.
Instead of presenting time series of the total sediment discharge, time series of the suspended sediment concentration are shown.
- Ladegaard-Pedersen P., Sigsgaard C., Kroon A., Abermann J., Skov K., Elberling B., Suspended sediment in a high-Arctic river: An appraisal of flux estimation methods, Sci Total Environ (2016), http://dx.doi.org/10.1016/j.scitotenv.2016.12.006
- Overeem, I., & Syvitski, J. P. M. (2008). Changing sediment supply in Arctic rivers. In Proceedings of a symposium held in Christchurch, New Zealand, December 2008, IAHS-AISH Publication. pp. 391–397.
- Turowski, J. M., Rickenmann, D., & Dadson, S. J. (2010). The partitioning of the total sediment load of a river into suspended load and bedload: A review of empirical data. Sedimentology, 57(4), 1126–1146. http://doi.org/10.1111/j.1365-3091.2009.01140.x