Projections of an Ice-Diminished Arctic Ocean - Retrospection and Future Projection

Jinlun Zhang, D. Andrew Rothrock, and Michael Steele Applied Physics Laboratory, University of Washington

Funded by The National Science Foundation Office of Polar Programs

Introduction

Significant changes in arctic climate have been detected in recent years. One of the most striking changes is the decline of sea ice concurrent with changes in atmospheric circulation and increased surface air temperature. This arctic warming trend, as consistently projected by global climate models (GCMs), is likely to continue into the future. The trend will lead to a diminished arctic sea-ice cover. Diminution of ice cover will greatly impact the regional and global climate. Less ice cover will also affect the socio-economic and ecosystems in the north polar region.

These NASA provided images show the minimum arctic sea ice concentration in 1979, at left, and in 2003. Satellite passive microwave data since the 1970s indicate a 3% decrease per decade in arctic sea ice extent.

The science goals of this NSF-funded project are:

GOAL 1: Examine the historical evolution of the arctic ice-ocean system from 1948 to 2003 to understand the large-scale changes that have occurred in sea ice and the upper Arctic Ocean over this time period.

GOAL 2: Project a diminished arctic sea-ice cover with multiple warming scenarios and to examine key linkages among atmospheric forcing, sea-ice processes, and oceanic processes in an ice-diminished Arctic Ocean and the adjacent seas.

Approach

To carry out these goals, researchers will use a global coupled ocean and sea ice model whose grid emphasizes the Arctic Ocean. A series of multi-decade model runs will be driven by both ‘reality-based’ and ‘future-based’ atmospheric forcing.The first stage of modeling will interpret the large-scale changes that have occurred in sea ice and the upper Arctic Ocean over the past five decades. To study the historical evolution of the arctic system, 1948-2003 reanalysis data with varying NAO/AO indices will be input into the model. The second stage of work will qualitatively and quantitatively examine when, where, and under what circumstances the arctic ice cover is likely to diminish or disappear in the future. Future forcings will be based on projections of plausible scenarios that are likely to lead to a significantly reduced ice cover. The initial conditions for all future projections runs will be based on the end state created by the retrospective run. The retrospective simulation results, in conjunction with available observations, will be compared to results from the projection runs in order to quantify the changes in an ice-diminished Arctic Ocean under various scenarios.

The project will also analyze changes in oceanic circulation and processes in an ice-depleted Arctic Ocean, and in its interactions with the sub arctic oceans.

In 1999 Rothrock, Yu and Maykut reported in Geophysical Review Letters that the average draught of the sea ice in the Arctic region had declined by 1.3 metres (4.3 ft) compared with the 1960s and 1970s. Ice draught is the difference between the surface of the ocean and the bottom of the ice pack.

Contact:

If you have any questions or require additional information, please contact Jinlun Zhang  (zhang©apl•washington•edu)  .