Daan van den Broek

agupubs.onlinelibrary.wiley.comSvalbard's Record‐Breaking Arctic Summer 2024: Anomalies Beyond Climatological Warming Trends2024 mean summer and August temperatures on Svalbard reached unprecedented levels, breaking previous records by record margins The August mean temperature falls outside of historically observed c...

16 Apr 2025

📚 Paper alert! 🧪 Thrilled to share my first scientific publication as a first author! "Svalbard's Record‐Breaking Arctic Summer 2024: Anomalies Beyond Climatological Warming Trends" is just out in Geophysical Research Letters, open access. agupubs.onlinelibrary.wiley.com/doi/full/10.... 🧵(1/5)

11h

It's always fascinating to watch the cold air expand across the Northern Hemisphere this time of year.❄️ GFS temperatures now vs. in 16 days (+384h).📉 Don't take the latter as a reliable forecast, but as an illustration of how rapidly northern regions cool in autumn. #WinterIsComing

@subfossilguy.bsky.social

13h

Polar night has started in Svalbard! 🌌 The sun won't rise until February 16th. With snow exclusively covering the mountian tops it's not quite winter yet, but with daylight disappearing, it will only be a matter of time.

Daan van den Broek reposted

Melaine Le Roy

Collapse of the spectacular ice cave (that formed at the front of #Morteratsch Glacier in 2024) as a result of insane melting of the 2026 summer! 🧊🔥🌡️ 📷 @landervt.bsky.social

theguardian.comTap water no longer drinkable in Norwegian town as climate-related thawing releases heavy metalsWarning for other Arctic communities as residents told not to use water in Longyearbyen in Svalbard, one of the fastest-warming places in the world

More problems with the drinking water supply in Longyearbyen, Svalbard. Residents have relied on separately treated water after elevated manganese last year. Now, nickel and sulphate levels also exceed recommended limits. Contamination likely due to thawing of permafrost.👇 🧵(1/3)

Svalbard is one of the fastest warming places on Earth, and in recent years, especially the summers have warmed dramatically. See our paper about the record-breaking heat of 2024. 👇 🧵(2/3)

Daan van den Broek@daanvandenbroek.com

cdnsciencepub.comPermafrost thermal regime and active layer dynamics across periglacial landforms in Svalbard's Nordenskiöld Land Permafrost Observatory, 2008–2023On Spitsbergen, Svalbard, the Nordenskiöld Land Permafrost Observatory provides ground temperature time series from 2008 to the present in 16 boreholes located in a variety of periglacial landforms. T...

The increase in summer temps, as well as the shorter winter season, affect active layer depth, the top part of the ground that does thaw in summer. This layer regionally increases around 10 cm/year in parts of Svalbard, see e.g.👇 cdnsciencepub.com/doi/full/10....

Beautiful frosty autumn morning in Helsinki/Vantaa. Minimum temperature: -3.3°C

This beauty produced a 57 m/s (205.2 km/h) wind gust at Hvammur in Iceland🇮🇸, wow! This is reportedly the highest gust on record at this location, outside the period of December-March.

🌡️ −16.7°C in Savukoski Tulppio: Finland’s lowest temperature this season. Chilly across the Ostrobothnian regions in the west too: −8.5°C at Ylivieska airport. Another cold, frosty morning across Finland! 🥶

Another frosty morning in the northern half of Finland.🥶 Coldest today: Muonio Oustajärvi at -13.3°C.

First signs of snow accumulation near Kajaani! ❄️❄️ Temperatures dropping towards 0°C in the most intense precipitation.

@mikarantane.bsky.social, if proper accumulation occurs, it should be the first snow of this autumn anywhere in Finland, correct?

Today is, climatologically, the fastest-cooling time of the year in Helsinki: the average seasonal temperature curve declines most rapidly around 9 October. For the nerds: this shows the time derivative of the 31-day-smoothed mean daily temperature. Winter is coming!❄️

Winter in Lapland🥶 And an impressive temperature gradient in Finland overall!

❄️ First snow of this autumn in Finland? ECMWF projects some snowfall for Kainuu and Kuusamo on Friday. Other models predominantly show rain. ⚠️ In any case, FMI issued warnings for bad driving conditions in those regions.

Peak ruska* outside the Finnish Meteorological Institute. 🍂🍁 * Ruska is a Finnish term for the colorful transformation of autumn foliage

Extreme weather in Crete. 🇬🇷 Torrential rains, regionally >100 mm in 2 hours. 🌧️ ⚠️ risk for flash floods, land- and mudslides, esp. in mountainous terrain. Code red is issued, and emergency notifications were sent out this morning for certain areas. 🚨

Despite some loud thunder last night, and a few showers this morning, the situation in Malia is relatively calm so far.⚡️ Emergency notifications are coming from different directions this morning, however.

No swimming in the sea today.

Daan van den Broek reposted

📚 Paper alert! Our paper "The 2026 cold wave brought northern Fennoscandia its coldest two-week period since 1987" is out now in Weather. 🧵(1/14)

Daan van den Broek reposted

Mika Rantanen

@mikarantane.bsky.social

New paper by @daanvandenbroek.com and me just published in @rmets.org Weather: "The 2026 cold wave brought northern Fennoscandia its coldest 2-week period since 1987" rmets.onlinelibrary.wiley.com/doi/10.1002/... Check out the brilliant thread by Daan below 👇

Daan van den Broek@daanvandenbroek.com

📚 Paper alert! Our paper "The 2026 cold wave brought northern Fennoscandia its coldest two-week period since 1987" is out now in Weather. 🧵(1/14)

📚 Paper alert! Our paper "The 2026 cold wave brought northern Fennoscandia its coldest two-week period since 1987" is out now in Weather. 🧵(1/14)

Finally, after 13 January, warm air advection from the south and increased mixing destroyed the inversion, warming the lower atmosphere again and marking the end of the cold wave. This event nicely demonstrated that extreme and persistent cold remains possible in a warming climate. 🧵(13/14)

For more information and details, read the complete article in Weather! 📄👇 🔗 doi.org/10.1002/wea.... 🧵End (14/14)

📚 Paper alert! Our paper "The 2026 cold wave brought northern Fennoscandia its coldest two-week period since 1987" is out now in Weather. 🧵(1/14)

The cold wave was initiated by strong cold-air advection from the north during the preceding week. The cold then intensified beneath a high-pressure system centred over northern Fennoscandia. 🧵(11/14)

Calm, clear-sky conditions under the high pressure system favored strong radiative cooling of the Earth's surface. Consequently, (near-)surface temperatures decoupled from warmer air above. The surface inversion strength in Sodankylä reached up to 30°C, as T2m reached low -30s and regionally -40s.

📚 Paper alert! Our paper "The 2026 cold wave brought northern Fennoscandia its coldest two-week period since 1987" is out now in Weather. 🧵(1/14)

- Savukoski Kirkonkylä and Sodankylä Lokka weather stations saw their coldest 14-day period since 1966. - Ylitornio Meltosjärvi was the most extreme: it measured the coldest 14-day period in its measurement history at -29.8°C, making it the coldest since at least 1964! 👇 🧵(9/14)

We note that the minimum temperature measured during this event is −42.8°C on 9 January. Extremely cold, but nowhere near a record low. This shows that the defining characteristic of this cold wave lies in the persistence of the extreme cold, not in individual minimum temperatures. 🧵(10/14)

📚 Paper alert! Our paper "The 2026 cold wave brought northern Fennoscandia its coldest two-week period since 1987" is out now in Weather. 🧵(1/14)

But: ERA5 spatial rankings show that the 2026 cold wave was among the most extreme in the dataset across a broad area of northern Fennoscandia. And the highest-ranked grid cells lie away from the long-term stations, suggesting those stations underestimate the regional severity of the cold.

Luckily, stations with shorter measurement series exist near this area, and those confirm that regionally, the cold was even more extreme. 👇 🧵(8/14)

📚 Paper alert! Our paper "The 2026 cold wave brought northern Fennoscandia its coldest two-week period since 1987" is out now in Weather. 🧵(1/14)

Temperature anomalies in this region reveal that the cold was most extreme in the border region between Finland and Sweden, with anomalies locally peaking below -18°C compared to the 1991-2020 average. Next, we analysed other long term weather stations in the region. 👇 🧵(5/14)

Sodankylä, 🇫🇮: coldest 14-day period since 1999 - together with that year, the coldest since 1987. Karesuando, 🇸🇪: coldest since 1980 (4th coldest in the full observational record -since 1879- at −31.8°C).🥶 Karasjok, 🇳🇴: less extreme as only the second coldest 14-day period this century, after 2014.

📚 Paper alert! Our paper "The 2026 cold wave brought northern Fennoscandia its coldest two-week period since 1987" is out now in Weather. 🧵(1/14)

We started by analysing Sodankylä weather station, the longest temperature time series in Northern Finland. At this station, the 14-day period between 31 Dec 2025 and 13 Jan 2026 was extremely cold, with 13 days below the 10th percentile of daily mean temperatures and a mean temp of -28.8°C.

We continued by looking at a regional perspective, based on ERA5 data. Here we found that the area averaged temperature over Northern Fennoscandia was the coldest since 1987, at -25.2°C. 🧵(4/14)

📚 Paper alert! Our paper "The 2026 cold wave brought northern Fennoscandia its coldest two-week period since 1987" is out now in Weather. 🧵(1/14)

doi.orgThe 2026 cold wave brought northern Fennoscandia its coldest 2‐week period since 1987During late December 2025 and January 2026, a severe and long-lasting cold wave affected northern Fennoscandia. In this article, we aim to quantify the extremity of the 2026 cold wave and evaluate…

Large areas of Lapland experienced their coldest two-week period since 1987. Regionally, those two weeks were even the coldest since at least 1964. 🥶 This work was carried out together with @mikarantane.bsky.social. 🔗 Read the full paper here: doi.org/10.1002/wea.... 🧵(2/14)

🌡️ ☀️ Exceptional warmth seems imminent late September and early October for western and northern Europe. Temperature anomalies of +10-+16°C are possible at 850 hPa (~1400 m altitude).

A strong southerly flow will estabilish between a deep trough over the Atlantic and a strong high pressure system over northern Europe, advecting very warm air. Sunny conditions under the high pressure system will add to the summer-like feeling. ☀️

10 Sept

Very heavy rainfall in northern Helsinki. The playground started to flood.

10 Sept

The purple pixel was responsible.

9 Sept

First year with a garden plot in northern Helsinki, and our pumpkin experiment certainly turned out successful. 🎃 Harvested on Sunday, before the weather turned too cold. Guesses for the weight?👇🏼

Daan van den Broek reposted

2 Sept

🌡️ Unsurprisingly, the Netherlands measured it's warmest summer on record, at an average temperature of 19.3°C. 2018 is now the 2nd warmest at 18.9°C. 8 out of the 10 warmest summers on record took place since 2003.

This summer measured 11 'tropical days' (Tx ≥ 30°C), 2 days short of the record from 1947 and 1976 (13). Interestingly, if we set the bar at 33°C, the summer of 2026 annihilated any other year.

2 Sept

At 36.8°C, de Bilt also measured its second highest annual maximum temperature. The record for the Bilt remains at 37.5°C, measured in 2019 - when southern and eastern parts of the Netherlands measured well over 40°C.

25 Aug

Last weekend's storm in the Baltics regionally dumped >100mm precipitation. According to @edhawkins.org, climate warming caused 15-20% more precipitation than would have been the case without warming.

Daan van den Broek@daanvandenbroek.com

🇱🇻 Various sources reported Latvia’s most destructive storm since January 2005. ⚡ ~160,000 customers without power at 21:00 🌳 Widespread fallen trees, blocked roads 🚆 Rail disruption 🌧️ Around half a month’s rain in one day (locally >100 mm)