The melting Greenland Ice Sheet and the implications for the ocean

The Greenland Ice Sheet (GrIS) loses mass through two main processes: ice sheet melt (and subsequent runoff) and iceberg calving. This thesis focuses on how these two processes affect the ocean at present, and how they are likely to change in the future, in the context of global climate change. To achieve this aim, three models of increasing complexity have been considered: the WERR control systems model, the FRUGAL ocean-iceberg model, and the NEMO ocean-iceberg model. The WERR model is combined with a new machine learning approach to forecast iceberg flux past the 48th parallel (I48N). This forecast is released to the International Ice Patrol each year. FRUGAL has been run five times, starting with the control run. Runs 2-5 include an additional meltwater component, varying over time. The ocean-iceberg model NEMO, has not been directly run for this thesis, instead outputs from an existing run (ORCA12-N512) have been analysed. This run has been forced with a high emission scenario with an approximate surface warming of 8.5 Wm-2 by 2100. Outputs from the FRUGAL and NEMO models are compared. It was found that runoff from the GrIS is likely to increase by 2050, while iceberg calving decreases. Additionally, it was found that I48N is likely to decrease in the future, however this will not necessarily reduce iceberg risk, as Arctic shipping is likely to increase over time. It was also found that increased runoff from the GrIS would have an impact on the strength of ocean circulation, but this will not necessarily result in wide-scale sea level rise by 2050. Instead, the relative increase/decrease in the strength of major ocean currents will cause a variable reaction in sea level. Nevertheless, with the associated exacerbation of extreme climatic events, increased global flooding would still occur.