Impact of changing ice and metocean conditions on offshore design and operations in the Arctic regions

The objective of the project has been to 1) review sea ice and related met-ocean conditions of importance for Arctic offshore operations, 2) quantify regional and interannual variability of the sea ice in different regions of the Arctic, and 3) assess future outlook for Arctic met-ocean conditions of importance for offshore design and operations based on climate model simulations.
The project has made a state-of-the-art review of scientific results regarding ice and met-ocean conditions in different parts of the Arctic Ocean. Results from new publications and studies are synthesised, with focus on sea ice and iceberg conditions as well as atmospheric and ocean processes with impact on the ice conditions. Analysis of satellite data and model simulations have been performed to study variability of the ice conditions in the Barents Sea, Kara Sea, East Siberian Sea, Chukchi Sea, Beaufort Sea and Greenland waters over the last 50 years. Scenarios for future changes of the Arctic climate by use of climate models have been investigated. Possible impact of projected changes in ice and metocean conditions on offshore design and operations in
different Arctic regions is discussed. Results of recent sea ice model simulation in the Arctic from 1958 to present based on ERA40
forcing fields from European Centre for Medium-range Weather Forecasting (ECMWF) are presented. This is the best reanalyzed atmospheric forcing fields available for the Arctic, extending back to 1958. These fields have been used to run the North-Atlantic model at NERSC, which consists of a Multi-Category ice model coupled to the HYCOM ocean circulation model. The Multi-
Category ice model treats the ice cover as a collection of ice floes in different thickness categories. This makes it possible to model the ice thickness probability density function for each grid cell. Ice thickness distribution gives a description of how much of the thickest ice generated by ridges is present in each grid cell. The model simulations from 1958 contains also ice drift and ice
concentration in every grid cell. The simulations have been analysed to retrieve regional, seasonal and interannual variability in the sea ice fields in response to the atmospheric forcing fields. Analysis of satellite data from 1979 to present shows a decrease in sea ice extent in all regional seas of the Arctic, although the interannual variability is the dominant feature in the ice extent data.

The recently published Fourth Assessment Report from IPCC has reinforced the conclusions on global warming as a consequence of increasing greenhouse gas emissions into the atmosphere. For the Arctic regions observations in the last decades shows that the sea ice cover decreases, the glaciers and ice sheets reduce their masses, the snow cover has decreased, and so have permafrost areas. Air temperatures are increasing in most areas and ocean temperatures have been observed to increase in areas such as the Fram Strait and the Barents Sea. However, long- term observations of the ocean are scarce, and we are lacking data to determine changes in the ocean water masses and circulation in the Arctic. Available data from the world oceans show increasing temperature over the last decades, with thermal expansion leading to sea level rise. Also melting of ice sheets, ice caps and glaciers contribute to the sea level change, but much less than the thermal expansion. IPCC states that the projections in the 21st century will be:
• The Arctic is very likely to warm during this century in most areas, and the annual mean warming is very likely to exceed the global mean warming. Warming is projected to be largest in winter and smallest in summer.
• Annual arctic precipitation is very likely to increase. It is very likely that the relative precipitation increase will be largest in the winter and smallest in summer.
• Arctic sea ice is very likely to decrease in extent and thickness. It is uncertain how the Arctic Ocean circulation will change.
In addition to the long-term trend it is important to be aware of decadal variability in the Arctic climate system. The understanding of the polar climate system and its variability is still incomplete due to its complex atmosphere-land-cryosphere-ocean interactions. The models used to simulate the global climate are not representing processes such as clouds, planetary boundary layer processes and sea ice. Planning of offshore operations in the Arctic need to consider that there is considerable uncertainty in the predictions of atmosphere, sea ice and ocean changes for the different regions of Arctic for the next decades.