THE CONTRIBUTION OF ARCTIC GLACIERS TO THE WATER CYCLE
CARTER, CARISSA L. INSTAAR.
Dyurgerov, Mark B. INSTAAR.
Glacier contribution to the Arctic Ocean has increased from 1960 to the present in response to climate change. Using updated time series (from Dyurgerov, 2002) for about 110 glaciers in the Arctic and Pan-Arctic totaling an area of 330,302 km2, we calculated temporal and spatial changes as well as variability in the mass balance of Arctic glaciers. We also approximated the cumulative contribution of glaciers relative to river runoff into the Arctic Ocean. The Greenland ice sheet is not part of our analysis, but individual ice caps around Greenland are included.
The role of glaciers in the Arctic water cycle is unique. In many cases, glacial runoff and river runoff can be analyzed separately. Available river runoff data from the Arctic covers areas where glacial meltwater contribution to river systems is negligible. The main Arctic rivers in Siberia, Eastern Europe, and North America, dominant fresh-water contributors to the Arctic Ocean, have very small glacial components. Conversely, more than 95% of glacier area in the Arctic covers archipelagoes (Canadian, Russian, and Svalbard) or other regions where no permanent gauging stations exist (R-ArcticNET, 2001), and therefore no river runoff data is available. This means that in the analyzed river discharge data, glacial meltwater is not included.
Changes in ice volume show large spatial variability, from mm in the Canadian Arctic to meters in Scandinavia, Iceland, and Svalbard (Fig. 1). Yearly volume fluctuations correspond to regional climate shifts. Glaciers in maritime climates, including Scandinavia and parts of Western Svalbard, have the largest variability in ice volume. In cold and dry regions such as the Canadian Arctic, year-to-year variability is small.
Volume loss in Arctic glaciers is accelerating. From 1960-76 glaciers were near a steady-state regime. The first shift towards accelerating mass loss occurred in 1976-77, the second, stronger shift, started at the end of the 1980s and continues today (Fig. 2) (McCabe et al., 2000 and Dyurgerov and Meier, 2000). Both shifts coincide with changes in atmospheric circulation patterns, the Arctic Oscillation, and increases in annual air temperature in the Northern Hemisphere.
Using data from more than 30 glaciers in the Pan-Arctic with relatively long-term mass balance records, we calculated the change in total glacier area over the last decades (Fig. 3). In sum, these glaciers lost approximately 40 km2, about 0.4% of their original area in 1961. Extrapolating these measured changes to other areas of small glaciers in the Arctic, the total area loss of glaciers in the Pan-Arctic is about 1300 km2.
We used river discharge data from the R-ArcticNET Hydrographic Data Network to calculate the average river runoff for the entire Arctic, in particular for regions where there are no glaciers, or where glacier area is negligibly small, in order to compare the contributions of both components to the Arctic Ocean. Annual glacial meltwater runoff (inflow) is small compared to annual runoff from the main Arctic rivers. However, the cumulative contribution of Arctic glaciers to the Arctic Ocean exceeds the net contribution of large Arctic rivers since 1961 (Fig. 4). We define glacier contribution as volume change: ¬DV, and river runoff contribution as a cumulative departure from the average: ¬(Ri - ), where Ri is the annual runoff in a year I, and is the average annual runoff from 1961-90. Until the end of the 1970ís, river runoff contribution was much larger than the cumulative Arctic glacier contribution, but after 1980 glacier contribution to the Arctic Ocean exceeded river contribution.
Temporal variability in glacier volume loss exceeds the year-to-year variability of river runoff (coefficient of variation is 4%) by an order of magnitude. This implies that in extreme climate conditions, glaciers intensify the water cycle in the Arctic.
In conclusion, these comparisons show that the cumulative effect of Arctic glacier volume loss (Greenland ice sheet not included) exceeded the cumulative contribution of river runoff to the Arctic Ocean from the early 1980ís to 1998. This indicates that river contribution to the Arctic Ocean and glacier contribution to the Arctic Ocean are intimately related to each other and to climate change, but determining the extent of the interplay of these variables will require further study.
Dyurgerov, M. B., 2002: Glacier Mass Balance and Regime: Data of
Measurements and Analysis. INSTAAR Occasional Paper #55, 268 pp., and
Dyurgerov, M. B. and Meier, M. F., 2000: Twentieth century climate change:
Evidence from small glaciers. Proceedings of National Academy of Sciences,
USA, 97, (4): 1406-1411.
McCabe, G. J., Fountain, A. G., and Dyurgerov, M. B., 1999: Effects of the
1976-77 climate transition on the mass balance of Northern Hemisphere
glaciers. Arctic, Antarctic and Alpine Research, 32 (1): 64-72.
R-ArcticNET: A Regional Hydrographic Data Network for the Pan-Arctic Region.
(v.2.1), NSIDC, 2001.
Figure 1. Spatial and temporal variability in glacier mass balance in select Arctic regions.
Figure 2. Volume change in select Arctic regions. Vertical lines indicate major climate shifts.
Figure 3. Surface area change for 30 selected glaciers.
Figure 4. Cumulative contribution of glaciers and rivers to the Arctic Ocean. Glacier contribution is volume change, and river contribution is the cumulative departure from the average runoff.
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