Andrew Bliss

Regional and global projections of twenty-first century glacier mass changes in response to climate scenarios from global climate models

A large component of present-day sea-level rise is due to the melt of glaciers other than the ice sheets. Recent projections of their contribution to global sea-level rise for the twenty-first century range between 70 and 180xa0mm, but bear significant uncertainty due to poor glacier inventory and lack of hypsometric data. Here, we aim to update the projections and improve quantification of their uncertainties by using a recently released global inventory containing outlines of almost every glacier in the world. We model volume change for each glacier in response to transient spatially-differentiated temperature and precipitation projections from 14 global climate models with two emission scenarios (RCP4.5 and RCP8.5) prepared for the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. The multi-model mean suggests sea-level rise of 155xa0±xa041xa0mm (RCP4.5) and 216xa0±xa044xa0mm (RCP8.5) over the period 2006–2100, reducing the current global glacier volume by 29 or 41xa0%. The largest contributors to projected global volume loss are the glaciers in the Canadian and Russian Arctic, Alaska, and glaciers peripheral to the Antarctic and Greenland ice sheets. Although small contributors to global volume loss, glaciers in Central Europe, low-latitude South America, Caucasus, North Asia, and Western Canada and US are projected to lose more than 80xa0% of their volume by 2100. However, large uncertainties in the projections remain due to the choice of global climate model and emission scenario. With a series of sensitivity tests we quantify additional uncertainties due to the calibration of our model with sparsely observed glacier mass changes. This gives an upper bound for the uncertainty range of ±84xa0mm sea-level rise by 2100 for each projection.

Global response of glacier runoff to twenty‐first century climate change

The hydrology of many important river systems in the world is influenced by the presence of glaciers in their upper reaches. We assess the global-scale response of glacier runoff to climate change, where glacier runoff is defined as all melt and rain water that runs off the glacierized area without refreezing. With an elevation-dependent glacier mass balance model, we project monthly glacier runoff for all mountain glaciers and ice caps outside Antarctica until 2100 using temperature and precipitation scenarios from 14 global climate models. We aggregate results for 18 glacierized regions. Despite continuous glacier net mass loss in all regions, trends in annual glacier runoff differ significantly among regions depending on the balance between increased glacier melt and reduction in glacier storage as glaciers shrink. While most regions show significant negative runoff trends, some regions exhibit steady increases in runoff (Canadian and Russian Arctic), or increases followed by decreases (Svalbard and Iceland). Annual glacier runoff is dominated by melt in most regions, but rain is a major contributor in the monsoon-affected regions of Asia and maritime regions such as New Zealand and Iceland. Annual net glacier mass loss dominates total glacier melt especially in some high-latitude regions, while seasonal melt is dominant in wetter climate regimes. Our results highlight the variety of glacier runoff responses to climate change and the need to include glacier net mass loss in assessments of future hydrological change.

Sublimation and surface energy budget of Taylor Glacier, Antarctica

Taylor Glacier, an outlet of the East Antarctic ice sheet, flows through the Transantarctic Mountains and terminates in the Dry Valleys. Understanding how this glacier fluctuates is important for studies of glacial geology, paleoclimate, ice dynamics and ecology. Sublimation is the primary mass-loss process for most of the glacier. Four years of specific balance measurements from the ablation zone show sublimation rates up to 40 cma−1. We used data from an array of weather stations as inputs to a model for latent heat flux and hence sublimation rate. Calculated and measured ablation rates agree to within uncertainties, indicating that wind speed and vapour pressure gradient (a function of temperature and humidity) are the governing variables, as expected from theory. Measurements and model results together allowed us to examine the spatial and temporal variations of sublimation on the glacier. On average, sublimation is about two times faster in summer than winter. Rapid sublimation occurs during storms and katabatic wind events, but such periods contribute less to the annual total than do slow, persistent losses. Spatially, sublimation reaches a maximum midway along the glacier, where descending surface air currents are focused by the topography of the aptly named tributary, Windy Gully.

A new inventory of mountain glaciers and ice caps for the Antarctic periphery

Abstract Although the glaciers in the Antarctic periphery make up a large fraction of all mountain glaciers and ice caps on Earth, a detailed glacier inventory of the region is lacking. We compile such an inventory, recording areas, area-altitude distributions, terminus characteristics and volume estimates. Glaciers on the mainland are excluded. The inventory is derived from the Antarctic Digital Database and some manual digitization. We additionally rely on satellite imagery, digital elevation models and a flowshed algorithm to classify ice bodies. We find 1133 ice caps and 1619 mountain glaciers covering a total of 132 867 ± 6643 km2. Estimated total volume corresponds to 0.121 ± 0.010 m sea-level equivalent. Of the total glacier area, 99% drains either into ice shelves (63%) or into the ocean (36%). The inventory will provide a database for glacier mass-balance assessments, modelling and projections, and help to reduce the uncertainties in previous studies.