During MOSAiC, one spring biological sample was named “Ridgey McRidgeFace” — and it made it into the final paper (doi.org/10.1038/s43247-026-03364-8). RMRF was a young ridge of thin first-year ice sampled in late March. The real challenge? Explaining what RMRF actually stands for.

Our graphic shows Arctic sea-ice ridges aren’t just rubble—they’re biomass hotspots. In summer, they can hold up to ~80–100% of ice-algal biomass despite covering much less area. Their complex structure creates diverse microhabitats for microbial life. doi.org/10.1038/s432... 🎨 Frida Cnossen

There are many colorblind-friendly, perceptually uniform colormaps (e.g., cmocean, @fabiocrameri.ch), yet many papers at @agu.org still use rainbow variants. Not just aesthetics — they can create artificial structures (see plot). Better options exist.

Some papers follow me into my nightmares. This study about the shape of pressure ridges claims that most of them are cusped (like an arrow tip). Not only is this counterintuitive, but when I checked the dataset used in the study, most ridges appeared to be either trapezoidal or irregular.

Can a portable device measure the full thickness of sea-ice pressure ridges? New preprint led by Polona Itkin @oceanseaicenpi.bsky.social tests ground-based electromagnetic induction (GEM) across all seasons. doi.org/10.5194/egus...

A blog post from Megan Lenss about our new paper on Antarctic sea-ice algae: ic3.uit.no/news/hidden-...

New nice preprint led by Dmitry Divine (@oceanseaicenpi.bsky.social) on #Arctic sea ice ridge volume in the Fram Strait, derived from moored sonar observations from 2012–2019: doi.org/10.5194/egus...

A new thesis about the inclusion of air bubbles into the mushy layer model of sea ice by Joseph Fishlock from the University of Oxford @ox.ac.uk: ora.ox.ac.uk/objects/uuid...

Back from the CONTRASTS expedition (July–Sept)! We studied 3 types of Arctic sea ice, revisiting each site 4 times. I wrote a short overview here: en.wikipedia.org/wiki/CONTRAS...

Unique concept for observing Arctic sea ice successfully implemented: AWI scientists were able to study different types of sea ice in parallel during the Polarstern expedition “CONTRASTS.” 🧊 www.awi.de/en/about-us/... Photo: Evgenii Salganik

Great to see a data paper from the Nansen Legacy cruises (2018–2022), led by Dmitry Divine (@oceanseaicenpi.bsky.social), including sea ice density measurements that clearly show strong seasonality: doi.org/10.1002/gdj3.70001

Our new data paper about under-ice observations from a remotely operated vehicle (ROV) during MOSAiC led by Philipp Anhaus from @awi.de: www.nature.com/articles/s41...

A new study led by Niels Fuchs uses hydrological models to predict the locations of melt ponds: doi.org/10.1029/2025GL115033

Our new study is out: The Arctic Beaufort Gyre is projected to weaken or vanish in most CMIP6 models under future climate change. The gyre would thus stop storing freshwater in its centre, with possibly large impacts on the Arctic and beyond. Read: agupubs.onlinelibrary.wiley.com/doi/full/10....

Ice Mass Balance (IMB) buoys are unique in their ability to distinguish between ice surface and bottom melt, which relates to the way solar energy is distributed. Models still do a poor job of capturing this. You can find the updated Wiki article here: en.wikipedia.org/wiki/Ice_mass_balance_buoy

If you are into Arctic sea ice thermodynamics, here is our new dataset of 82 CRREL ice mass balance buoys deployed in 1997–2024 with estimates of snow and ice thickness and their interface evolution: doi.org/10.5281/zenodo.15096485

If you are into modeling of sea ice physical properties (salinity, brine volume, or density), we combined coring datasets to have a seasonal evolution for first- and second-year level ice: doi.org/10.5281/zeno... The coring datasets have many more parameters, including isotopes and nutrients.

In summer we typically track sea ice melt, assuming its height above the waterline decreases. In our new study, we show that sea ice freeboard may increase during the advanced melt in June and July due to the rapid decrease of ice density. Read more: doi.org/10.5194/tc-19-1259-2025

Last day at the Norwegian Polar Institute. Thanks for the good memories.

Yesterday, you showed Zack's beautiful work to your colleague; today, he no longer works at NOAA. Huge support. We all live in an evolving dystopia.

Shocking. It is hard to overestimate the importance of all the wonderful research and observations from NOAA @climate.noaa.gov and other US-based agencies. Huge support to Zack and others who are affected.

Fate of #Arctic sea ice melt | In a new study led by @madm-ice.bsky.social, we followed the #MOSAiC ice floe and calculated the budget of freshwater sources and sinks from snow and ice melt in summer 2020. Read more: doi.org/10.5194/tc-19-619-2025

Impressive airborne measurements of ice ridge spacing led by Thomas Krumpen:

Academic journals may need stricter guidelines for introductions. Broad overviews with ambiguous claims and irrelevant references are way too common. Worse, unjustified citations of colleagues and co-authors further devalue citations, as if they can get less valuable than now.

If only they could have asked the author. The sea-ice density part is not much better. Half-based on a 1978 study published in Russian and not publicly available.

The only problem with Fabio's color maps is that they are so beautiful it is hard to choose one.

Our sea ice and ocean sections of Norwegian Polar Institute on Bluesky:

Quote from WMO sea ice nomenclature: "Ice ridge concentration: Concentration (aerial coverage) of hummocked ice of all kinds in an ice area in tenths." Should it be areal instead of aerial? @wmo-global.bsky.social, we can do better.

A great new study led by Thomas Krumpen about the decrease of ridge density based on airborne observations since the 1990s:

Presenting our work on sea-ice ridge thermodynamics during winter and summer at @agu.org was a pleasure. You can check out our #AGU24 talk here: www.youtube.com/watch?v=gUFi...

Our work with Odile Crabeck and Jack Landy about the rapid decrease of sea-ice density in summer leading to non-decreasing ice freeboard during 0.6 m ice thickness loss: doi.org/10.5194/egus...

The ecosystem work overview of the MOSAiC expedition led by Allison Fong is published at Elementa: Science of the Anthropocene: doi.org/10.1525/elem...

Great start of the MOSAiC conference in Potsdam with the team ocean work overview by @clnhz.bsky.social

Sea ice cores from the MOSAiC expedition were finally CT-scanned at the European Synchrotron in Grenoble at their natural temperatures when they were collected during the 2019–20 season: www.esrf.fr/home/news/ge...

First morning at European Synchrotron before scanning some MOSAiC sea ice with Sönke Maus from NTNU and Martin Schneebeli from @slfdavos.bsky.social

Norwegian universities announced their tuition fees for non-EU students. The NTNU annual fee is €43,000 for medicine and €22,500 for technology. It is too high and not supported by educational quality or rankings. Which would mean there will be no non-EU students in Norway.

If thicker ice melts faster, does it apply to pressure ridges? Ridge flanks also show a good 60% correlation between melt and draft. But for the ridge bottom part, the correlation is much weaker (only 20%), as its melt also depends on ridge width and slope.

How often have you heard that thinner ice melts faster? Our measurements of ice melt from the Alfred Wegener Institute ROV underwater sonar show that it is quite the opposite, with a 45% correlation between first-year ice melt and its initial draft:

One of my guilty pleasures is updating Wikipedia about my favorite topics. I like imperfect Wiki for being neutral by design, written by hundreds of authors with diverse worldviews, and looking like scientific papers, as everything should be referenced. This is from the page about false bottoms:

When sea ice melts, even after snow is gone, it looks like snow because of the meltwater drainage. In the new study by @madm-ice.bsky.social et al., they describe the albedo of this "surface scattering layer", how fast it can form from bare ice, and how it affects ice melt: doi.org/10.1029/2022...

Arctic sea ice drifts around twice as fast during the summer (Olason and Notz, 2014). Its drift speed correlates with ice thickness at high ice concentrations. But during the summer, ice also loses its roughness as thicker ice melts faster (color map is from @fabiocrameri.ch):

A single number is not enough to understand ridge melt enhancement. Some of our ridge cross-sections melted by only 0.2 m, while others by 2.6 m. So we also showed key characteristics defining ridge melt. Deeper, narrower, and steeper ridges melt faster. The largest melt occurs at the ridge corners.

Our new @eurogeosciences.bsky.social Cryosphere study shows strong differences in melt rates of the main sea-ice types using multibeam sonar surveys during the MOSAiC expedition, with a substantial enhancement of ridge melt: doi.org/10.5194/tc-1...

We compared Fram Strait sea-ice ridge shapes from ROV sonar with moored sonar measurements from Ekeberg et al. (2014). On average, we had a two-times wider bottom ridge width, covering 38% of the total width, yet 10% of cross-sections were absolutely not trapezoidal:

Sea-ice ridges are often thought of as lines with trapezoidal cross-sections but in 3D they look quite more complex: