iiinova — where your digital self keeps evolving

Christoph Renkl @christophrenkl.org · 27/08/2026

Nice collaboration between folks at @utokyoofficial.bsky.social, National Institute for Environmental Studies, @soest.hawaii.edu, @unibonn.bsky.social, and @whoi.edu. 6/6

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Christoph Renkl @christophrenkl.org · 27/08/2026

🐟 Why this matters: Vertical transport in small bays and estuaries shapes how nutrients and other materials move through the water column. Models that only capture coastal or curl-driven upwelling may be missing a real pathway in the bay interior. 5/🌊

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Christoph Renkl @christophrenkl.org · 27/08/2026

💨 On timescales shorter than the inertial period, this upwelling is driven by wind stress divergence — short, fast bursts of local wind variability triggering a rapid oceanic response rather than weaker curl-driven Ekman upwelling, acting at longer timescales. 4/🌊

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Christoph Renkl @christophrenkl.org · 27/08/2026

⤴️ With high-resolution wind forcing, upwelling not only occurs along the coastline, but also in the interior of the bay, resulting in a more realistic distribution of surface salinity in the model. 3/🌊

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Christoph Renkl @christophrenkl.org · 27/08/2026

🔎 Comparing high-resolution (100 m grid spacing) simulations of coastal circulation in Otsuchi Bay in Japan — one forced with downscaled, spatially varying winds and the other one using spatially uniform wind — reveals that realistic wind variability across the bay improves the model skill. 2/🌊

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Christoph Renkl @christophrenkl.org · 27/08/2026

Is it important to force very high-resolution ocean models of small coastal bays and estuaries using wind forcing with matching resolution? Short answer: Yes! 📄 Our new paper led by Yoo-Jun Kim, recently published in @jgroceans.bsky.social, provides more insights: 🔗 doi.org/10.1029/2026... 1/🌊

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Reposted by Christoph Renkl

John Kennedy @micefearboggis.bsky.social · 10/08/2026

It's striking how similar are the patterns of the highest and lowest temperature anomalies in the northern hemisphere in June 1976 and June 2026 and also how much warmer 2026 is overall. Not an original idea, but unusually clear example of how a similar weather pattern is much warmer now than then.

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Christoph Renkl @christophrenkl.org · 26/07/2026

This is a result of a collaboration with Hyodae Seo (@soest.hawaii.edu) and Art Miller (@scrippsocean.bsky.social) during my postdoc at @whoi.edu and lays the foundation for future projects of my research group at @unibonn.bsky.social. /fin

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Christoph Renkl @christophrenkl.org · 26/07/2026

📈 With projected increases in frequency, intensity, and duration of marine heatwaves under continued climate warming, our study implies a growing potential for SST anomalies to precondition the atmosphere for more intense AR events, increasing the likelihood of compound ocean–atmosphere extremes. /4

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Christoph Renkl @christophrenkl.org · 26/07/2026

🌧️ When they reached the coast California this lead to an estimated 19-55% increase in precipitation increase relative to the simulations without the marine heatwave. 🔍 This intensification of the atmospheric rivers was driven primarily by direct thermodynamic effects. /3

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Christoph Renkl @christophrenkl.org · 26/07/2026

🌊 Warm SST anomalies increased evaporation and latent heat flux by up to 60% in some regions, adding more moisture to the lower atmosphere. 💨 This extra moisture strengthened the atmospheric rivers, with increases in integrated water vapor transport of more than 50% at times. /2

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Christoph Renkl @christophrenkl.org · 26/07/2026

What happens to #AtmosphericRivers when they interact with #MarineHeatwaves? Our new paper now out in @natureportfolio.nature.com Scientific Reports provides an answer. We assessed the impact of “the #Blob” on landfalling atmospheric rivers on the North American west coast. Here is what we found 🧵

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Christoph Renkl @christophrenkl.org · 28/01/2025

The time series above show variations of coastal MDT, alongshore current, and derived quantities on timescales >15 days. Tidal signals are averaged out (we checked that there is no aliasing).

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Christoph Renkl @christophrenkl.org · 27/01/2025

This highlights the value of using geodetic MDT estimates for model validation and ocean monitoring, making this study relevant for both the modeling and observation communities. 🌊 (5/5)

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Christoph Renkl @christophrenkl.org · 27/01/2025

Combining theory, idealized models, and a regional ocean circulation model, we offer two complementary and dynamically consistent interpretations linking this tilt of MDT to the alongshore current and also to the area-integrated nearshore circulation. (4/5)

Low-pass-filtered time series of the alongshore tilt of MDT at the coast of Nova Scotia and related quantities. (a) Mean alongshore depth-averaged current predicted by GoMSS (blue) and estimated from wind-corrected tilt of predicted MDT (black). (b) predicted by GoMSS (black), diagnostic of area-integrated nearshore circulation (red), area-integrated JEBAR (blue), and flow across isobaths (green). The model output was integrated over the area enclosed by the red polygon in Fig. 1. A third-order Butterworth low-pass filter with a cutoff frequency of 15 d was applied to the time series to remove high-frequency variability and thereby allow a quasi-steady state to be assumed.

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Christoph Renkl @christophrenkl.org · 27/01/2025

This includes an alongshore tilt of MDT associated with the Nova Scotia Current that is balanced primarily by wind stress, bottom friction, and a small contribution from lateral mixing. (3/5)

Predicted MDT (black line) and contributions by individual terms in the alongshore, depth-averaged momentum balance at the coast on the Scotian Shelf: wind stress (ηW), bottom friction (ηBF), and lateral mixing (ηLM) as well as their sum. The contribution from the depth-averaged baroclinic pressure gradient is also shown (gray line). Note that the mean of each term has been subtracted to center the curves around zero. Alongshore locations of the tide gauges are shown by their respective abbreviation.

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Christoph Renkl @christophrenkl.org · 27/01/2025

MDT (the local height of sea level above the geoid) can be estimated by coastal tide gauge observations in combination with the latest generation of geoid models. These new geodetic estimates can be used to validate MDT predictions by regional high-resolution ocean models. (2/5)

Predicted and observed mean dynamic topography (MDT). (a) MDT predicted by GoMSS (spatial median value over an area where water depth < 200 m is removed). Markers indicate the locations of the coastal tide gauges listed in Table 1. The line separates the upper Bay of Fundy where the model has difficulty resolving the residual circulation due to the limited resolution. (b) Coastal MDT as a function of distance along the coast of the Gulf of Maine and Nova Scotia. The minima in Minas Passage (−28 and −25 cm, respectively) are not shown. Geodetic estimates of MDT are shown with their respective uncertainty. The shaded area indicates the coast along the upper Bay of Fundy. Panels (c) and (d) show enlarged views of either side of the shaded area in (b). In panels (b)–(d), the means of the respective observations and predictions at the grid points closest to the tide gauges have been removed.

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Christoph Renkl @christophrenkl.org · 27/01/2025

🚨New Paper!🚨 Coastal mean dynamic topography (MDT) can provide a direct estimate of the average alongshore current and also a measure of area-integrated nearshore circulation. 🌊 Our #EGUhighlights paper in Ocean Science has the details - short summary below. (1/5) doi.org/10.5194/os-2...

doi.org

The alongshore tilt of mean dynamic topography and its implications for model validation and ocean monitoring

Abstract. Mean dynamic topography (MDT) plays an important role in the dynamics of shelf circulation. Coastal tide gauge observations in combination with the latest generation of geoid models are prov...

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Christoph Renkl @christophrenkl.org · 09/12/2024

Very excited to be at #AGU24 this week! I’m looking forward to lots of science, meeting old friends, and making new connections. Let’s get in touch! Here’s where you can find me:

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Reposted by Christoph Renkl

Jacob Wenegrat @roguewave.bsky.social · 26/09/2024

Gold wrote a brief BAMS note about this in 1963, in response to a request from Phillips. He notes that he believes the earliest note was in a glossary of his 1907 paper, where there was some evident advantage in separating the Coriolis component from the centrifugal effect in gradient wind 2/🌊

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Christoph Renkl @christophrenkl.org · 07/05/2024

The model also predicts that the atmospheric circulation in response to the MJO leads to anomalous upwelling on the Scotian Shelf. (5/5)

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Christoph Renkl @christophrenkl.org · 07/05/2024

The observed relationship between the MJO and North Atlantic SST can be captured by a regional ocean circulation model demonstrating their feasibility and potential for S2S ocean prediction. (4/5)

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Christoph Renkl @christophrenkl.org · 07/05/2024

These changes are driven primarily by anomalous air-sea heat fluxes caused by large-scale atmospheric perturbations linked to the MJO. (3/5)

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Christoph Renkl @christophrenkl.org · 07/05/2024

Statistically significant large-scale #SST changes in the North #Atlantic, particularly along the eastern seaboard of North America, can be related to the MJO. (2/5)

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