Tricentennial trends in spring ice breakups in three rivers in northern Europe

In Finland, ice breakup observations have been recorded for centuries for Aura River (1749–2020), Torne River (1693–2020) and Kokemäki River (1793–2020). The Kokemäki River is a newly revised, extended, and updated ice breakup series from Pori. The Spearman analysis shows that the correlation between Aura and Kokemäki rivers is strong, while the correlation between the two southern rivers (Aura and Kokemäki) and Torne River is weaker. The difference is attributed to the longitudinal distance between the rivers. Temperature correlations are strong for all three rivers and the long-term trends towards earlier breakups are statistically significant. Aura and Kokemäki rivers show considerable changes. Aura and Kokemäki river have had two respectively three years without a complete ice cover in the 21st century. These are the first non-freeze events in over 270 years of recorded observations. In Torne River, however, the earliest recorded breakup date has changed only marginally the last 100 years. Moreover, the earliest recorded breakup date in the 21st century occurred only five days earlier than the earliest breakup date in the 18th century. Kokemäki River did not escape the hydroelectric power plant boom in the mid-1900s, and this has speeded up the breakup process. A qualitative analysis shows that exceptionally late ice breakups occurred in all three rivers in 1807, 1810 and 1867. There are noticeable clusters of late events in the early 1800s in all three series, while an exceptionally early breakup event occurred in Aura and Kokemäki rivers in 1822.

Warming Climate Shortens Ice Durations and Alters Freeze and Breakup Patterns in Swedish Water Bodies

Increasing air temperatures reduce the duration of ice cover on lakes and rivers, altering their water quality, ecology, biodiversity, and physical, economical and recreational function. Using a unique in-situ record of freeze and breakup dates, including records dating back to the beginning of the 18th century, we analyze changes in ice duration (i.e., first freeze to last breakup), freeze and breakup patterns across Sweden. Results indicate a significant trend in shorter ice duration (62 %), later freeze (36 %) and earlier breakup (58 %) dates from 1913–2014. In the latter 3 decades, the mean observed ice durations have decreased by about 11 days in northern (above 60N) and 28 days in southern Sweden, whereas the average freeze date occurred about 10 days later and breakup date about 17 days earlier in southern Sweden. The rate of change is roughly twice as large in southern Sweden as in its northern part. Sweden has experienced an increase in occurrence of years with an extremely short ice cover duration (i.e., less than 50 days), which occurred about eight times more often in southern Sweden than previously observed. Our analysis indicates that even a 1 °C increase in air temperatures in southern (northern) Sweden results in a mean decrease of ice duration of 22.5 (7.6) days. Given that warming is expected to continue across Sweden during the 21st century, we expect increasingly significant impacts on ice cover duration and hence, ecology, water quality, transportation, and recreational activities in the region.

Climate change and sea ice: Shipping accessibility on the marine transportation corridor through Hudson Bay and Hudson Strait (1980–2014)

Shipping traffic has been increasing in Hudson Strait and Hudson Bay and the shipping route through these waters to the Port of Churchill may soon become a federally-designated transportation corridor. A dataset on passive microwave-based sea ice concentration was used to characterize the timing of the ice on the shipping corridor to the Port between 1980 and 2014. Efforts were made to produce results in a readily accessible format for stakeholders of the shipping industry; for example, open water was defined using a sea ice concentration threshold of ≤ 15% and results are presented in terms of real dates instead of anomalies. Between 1980 and 2014, the average breakup date on the corridor was July 4, the average freeze-up date was November 25, and the average length of the open water season was 145 days. However, each of these three variables exhibited significant long-term trends and spatial variability over the 34-year time period. Regression analysis revealed significant linear trends towards earlier breakup (–0.66 days year–1), later freeze-up (+0.52 days year–1), and a longer open water season (+1.14 days year–1) along the shipping corridor between 1980 and 2014. Moreover, the section of the corridor passing through Hudson Strait displayed significantly stronger trends than the two sections in Hudson Bay (i.e., “Hudson Islands” and “Hudson Bay”). As a result, sea ice timing in the Hudson Strait section of the corridor has diverged from the timing in the Hudson Bay sections. For example, the 2010–2014 median length of the open water season was 177 days in Hudson Strait and 153 days in the Hudson Bay sections. Finally, significant linear relationships were observed amongst breakup, freeze-up, and the length of the open water season for all sections of the corridor; correlation analysis suggests that these relationships have greatest impact in Hudson Strait.

Time Scale Variation of the Yellow River Ice in the Inner Mongolia Section Using Wavelet Analysis

Due to the comprehensive effects of thermal factor, power factor, river course factor and human factor, indicated that ice information, such as flow ice date, frozen river date, breakup date of river ice and ice thick and so on presents complex change, this article attempts to analyze ice information whether has varied characteristic in the time criterion with the wavelet method. Through analyzing wavelet transform coefficient and wavelet variance in Inner Mongolia section, and the time series rules are summarized of ice characteristic. At the same time, wavelet variational figures and wavelet transformation frequency variance figures are drawn of Inner Mongolia station. Research results show that flow ice date sequence have obvious frequency variance extreme value of about 12 years criterion, therefore said that flow ice date exists about 12 years cycle, frozen river date and breakup ice date sequence have not remarkable frequency variance extreme value, but there is no obvious peak in about 6 years place of frozen river date frequency variance and in about 12 years place of breakup ice date frequency variance, which explained that frozen river date and breakup ice date sequence exist weak cycle.

Large-Scale Climate Controls of Interior Alaska River Ice Breakup

Frozen rivers in the Arctic serve as critical highways because of the lack of roads; therefore, it is important to understand the key mechanisms that control the timing of river ice breakup. The relationships between springtime Interior Alaska river ice breakup date and the large-scale climate are investigated for the Yukon, Tanana, Kuskokwim, and Chena Rivers for the 1949–2008 period. The most important climate factor that determines breakup is April–May surface air temperatures (SATs). Breakup tends to occur earlier when Alaska April–May SATs and river flow are above normal. Spring SATs are influenced by storms approaching the state from the Gulf of Alaska, which are part of large-scale climate anomalies that compare favorably with ENSO. During the warm phase of ENSO fewer storms travel into the Gulf of Alaska during the spring, resulting in a decrease of cloud cover over Alaska, which increases surface solar insolation. This results in warmer-than-average springtime SATs and an earlier breakup date. The opposite holds true for the cold phase of ENSO. Increased wintertime precipitation over Alaska has a secondary impact on earlier breakup by increasing spring river discharge. Improved springtime Alaska temperature predictions would enhance the ability to forecast the timing of river ice breakup.

Long-Term Changes in Ice Phenology of the Yellow River in the Past Decades

The authors quantitatively describe the changes in the characteristics of ice phenology including the flow rate and freeze/breakup dates of the Yellow River based on observations of the past 50 yr. In both the upper and lower reaches of the Yellow River, increasing temperature delays the freeze date and advances the breakup date, thus decreasing the number of freeze days and the expanse of river freeze. From 1968 to 2001, the freeze duration has shortened significantly by 38 days at Bayangaole and 25 days at Sanhuhe, respectively. From the early 1950s to the early 2000s, the changes in freeze and breakup dates have shortened the freeze duration in the lower reach of the Yellow River by 12 days. The flow rate has reduced from 500 to 260 m3 s−1, and the expanse of river freeze has also decreased significantly by about 310 km. In addition, in the lower reach of the river, the location of earliest ice breakup has shifted downstream significantly in the last 50 yr, although the location of earliest freeze exhibits little change.