Understanding changes in Iceland's streamflow dynamics in response to climate change.
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| Title: | Understanding changes in Iceland's streamflow dynamics in response to climate change. |
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| Authors: | Helgason, Hordur Bragi1,2 (AUTHOR) hordur.helgason@landsvirkjun.is, Gunnarsson, Andri1 (AUTHOR), Sveinsson, Óli G. B.1 (AUTHOR), Nijssen, Bart2 (AUTHOR) |
| Source: | Hydrology & Earth System Sciences. Jun2026, Vol. 30 Issue 12, p3979-3999. 21p. |
| Subject Terms: | *Streamflow, *Hydrology, *Water power, *Glacial melting, *Climate change, *Water management, *Precipitation anomalies |
| Geographic Terms: | Iceland |
| Abstract: | The hydrological cycle in high-latitude regions is undergoing significant changes due to climate change. Iceland, with its long-term records from minimally disturbed catchments, provides a unique opportunity to study these changes. The country's heavy reliance on hydropower, without interconnections to other electricity markets, makes understanding these changes critical. We analyzed streamflow records from 25 gauges (1973–2023) and 37 gauges (1993–2023) in the LamaH-Ice dataset, alongside ERA5-Land reanalysis data, to assess climate-driven changes in annual, seasonal, and intra-annual flow regimes. Interannual variability remains high, with multi-year fluctuations strongly linked to the Arctic Oscillation. Significant warming has occurred in both periods, and precipitation has increased, with the most pronounced intensification in September. Precipitation has transitioned from a snowfall-dominated to a rainfall-dominated regime, with an abrupt shift around 2000. Over 1973–2023, statistically significant increases in annual discharge were observed in approximately one-third of catchments, while most others showed non-significant upward tendencies. Over 1993–2023, significant increases were limited to roughly one-seventh of catchments, although most others still trended upward. Seasonally, fall and winter showed the strongest and most widespread increases over the period 1973–2023, and the centroid of annual flows occurred significantly earlier. Over 1993–2023, spring and fall showed the largest increases. Summer trends were rarely significant but predominantly negative, especially in surface-fed rivers. In glaciated catchments, melt-season discharge increased over 1973–2023 but shifted toward negative tendencies over 1993–2023, consistent with a recent North Atlantic cooling anomaly and reduced glacier melt. Hydrological variability declined, with consistent reductions in coefficients of variation and flashiness. The proportion of baseflow in total discharge exhibited a coherent tendency toward increase, with significant rises at a minority of sites – more common over the longer record than in the shorter, more recent period. Across both periods, baseflow acted as a hydrological buffer, dampening flow declines in summer and moderating increases in winter and spring. These findings indicate that Iceland's hydrology is transitioning toward higher cool-season discharge and emerging summer reductions under a rainfall-dominated climate, with broader implications for reservoir operations and water resources management. This study enhances our understanding of Icelandic hydrology and contributes to global knowledge on climate-induced hydrological changes. [ABSTRACT FROM AUTHOR] |
| Database: | Energy & Power Source |
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