Highest altitude a t which thinning occurred m Dimensions depend on form of the calving relation.

Researchers are increasingly interested in understanding the impact of contentious social processes on land change. In the Brazilian Amazon, there are often contentious interactions between landholders defending private property rights and squatters who have the right to occupy land that is deemed unproductive. Previous studies suggest that the contentious social processes inherent in the Brazilian land tenure and land reform system cause a significant amount of deforestation. An environment of insecure land title, and policies that value deforested land over forested land, among other factors, encourage both landholders and squatters to deforest more land than is necessary for pasture or crop production. This paper examines the impact that land occupations have on deforestation at the municipal scale across the Brazilian Legal Amazon, from 2000-2009. We show that land occupations have a direct influence on deforestation. We use spatial analysis as well to show that land occupations have a spatial component in the effect on deforestation: occupations in one municipality affect deforestation in adjacent areas.

Grounded, iceberg-calving glaciers terminating in shallow water advance or retreat slowly; those terminating in deep (>80 m) water retreat rapidly (>.5 km/y, table 1). Columbia Glacier is retreating off a terminal-moraine shoal so that the water depth at its terminus is deepening with time. This report predicts that the rate of retreat of Columbia Glacier will accelerate during the next two or three years, and that the annual discharge of icebergs will increase to a peak of about 8-11 km 3 /y (6-8 times the 1978 value) in the period 1982 to 1985 (figure 8). This prediction has an uncertainty of timing of at least one year. The maximum rate of calving is expected to be in late summer. It is expected that the glacier will have retreated about 8 km by 1986, and that retreat will continue for several decades. This prediction could be refined markedly by comparing the predictions with new monitoring activities on the glacier.

Mount Baker, North Cascades, WA, has a current glacierized area of 38.6 km2. From 1984 to 2010, the North Cascade Glacier Climate Project has monitored the annual mass balance (Ba), accumulation area ratio (AAR), terminus behaviour and longitudinal profiles of Mount Baker glaciers. The Ba on Rainbow, Easton and Sholes Glaciers from 1990 to 2010 averaged −0.52 m w.e. a−1(m a−1). Terminus observations on nine principal Mount Baker glaciers, 1984–2009, indicate retreat ranging from 240 to 520 m, with a mean of 370 m or 14 m a−1. AAR observations on Rainbow, Sholes and Easton Glaciers for 1990–2010 indicate a mean AAR of 0.55 and a steady state AAR of 0.65. A comparison of Ba and AAR on these three glaciers yields a relationship that is used in combination with AAR observations made on all Mount Baker glaciers during 7 years to assess Mount Baker glacier mass balance. Utilizing the AAR–Ba relationship for the three glaciers yields a mean Ba of −0.55 m a−1 for the 1990–2010 period, 0.03 m a−1 higher than the measured mean Ba. The mean Ba based on the AAR–Ba relationship for the entire mountain from 1990 to 2010 is −0.57 m a−1. The product of the mean observed mass balance gradient determined from 11 000 surface mass balance measurements and glacier area in each 100‐m elevation band on Mount Baker yields a Ba of −0.50 m a−1 from 1990–2010 for the entire mountain. The median altitude of the three index glaciers is lower than that of all Mount Baker glaciers. Adjusting the balance gradient for this difference yields a mean Ba of −0.77 m a−1 from 1990 to 2010. All but one estimate converge on a loss of −0.5 m a−1 for Mount Baker from 1990 to 2010. This equates to an 11‐m loss in glacier thickness, 12–20% of the entire 1990 volume of glaciers on Mount Baker. Copyright © 2012 John Wiley & Sons, Ltd.

Ice velocity data are presented for the lower reach of Columbia Glacier, Alaska. The data span a 29 day period and contains 1,072 angle sightings from two survey stations to 22 markers placed on the ice surface, and 1,621 laser measurements of the distance to one of those markers (number 11) from another station. These short-interval observations were made to investigate the dynamics of the glacier and to provide input to models for estimation of future retreat and iceberg discharge. The mean ice velocity (at marker number 11) was approximately 9 meters per day and ranged from 8 to >15 meters per day. The data set includes a well defined 2-day 50-percent velocity increase and a clear pattern of velocity fluctuations of about 5 percent with approximately diurnal and semidiurnal periods.