The arctic ice thickness anomaly of the 1990s: A consistent view from observations and models

[1] Observations of sea-ice draft from submarine cruises in much of the Arctic Ocean show that the ice cover was unusually thin in the mid-1990s. Here we limit our examination to digitally recorded draft data from eight cruises spanning the years 1987 to 1997 and find a decrease of about 1 m over the 11-year span. Comparisons of our modeled draft with observed draft show good agreement in the temporal change. Comparing average draft over entire cruises, the RMS discrepancy between modeled and observed draft is 0.3 m and the correlation is 0.98. Agreement in the spatial patterns of draft is somewhat lower; the RMS discrepancy of 50-km averages of draft is 0.7 m and the correlation is 0.73. We review reports of interannual variations of ice thickness or volume from other model studies. All models agree that thickness decreased by between 0.6 and 0.9 m from 1987 to 1996. Our model shows a modest recovery in thickness from 1996 to 1999. For the 1950s, 1960s, and 1970s, models tend to disagree on the size and to a lesser extent the timing or phase of interannual variations.