Ulrike Löptien

Barents Sea atlantification driven by a shift in atmospheric synoptic timescale

Ulrike Löptien — Fri, 02 Jan 2026 20:05:12 +0000

In a European collaboration with French, Norwegian, Lithuanian, and German colleagues, the riddle why a pronounced simulated trend occurred at Barents Sea opening at has now been solved in Nature Clime Change.

Footsteps of the Phoenicians

Ulrike Löptien — Tue, 25 Nov 2025 16:29:51 +0000

Not only modern humans, but also the Phoenicians were strongly impacted by climate. An interdisciplinary project revealed fascinating perspectives.

Major Baltic Inflows come in different flavours

Ulrike Löptien — Thu, 03 Apr 2025 08:54:49 +0000

The Baltic Sea is a marginal sea in northern Europe. Anthropogenic eutrophication and related deoxygenation are among its pressing environmental problems. In this context, North Sea water plays a crucial role in maintaining the ecological balance as so called Major Baltic Inflows from the North Sea are the only mechanism to ventilate the deep waters of the Baltic with fresh oxygen. Based on machine learning we could identify two types of inflows depending on the driving temporal evolution of atmospheric synoptics – either the inflowing water is relatively salty or fresh which directly affects its capability to oxygenate the deep Baltic Sea..

https://www.nature.com/articles/s43247-025-02209-0

How to diagnose ocean mixing in models

Ulrike Löptien — Thu, 06 Mar 2025 13:12:08 +0000

Ocean mixing is key to distribute heat and nutrients in the world oceans. Despite it’s great importance, it is mainly unconstrained even in ocean models, where numerical effects add to the deliberate parameter settings. Our novel study proposes to use the saturation state of the noble gas Argon to diagnose mixing in ocean models. We test this approach in a suite of model versions of the North Atlantic Ocean off Mauritania https://bg.copernicus.org/articles/22/1215/2025/

Using AI to understand Barents Sea transports

Ulrike Löptien — Mon, 13 Jan 2025 16:50:24 +0000

A close cooperation with Norway and Estonia explores the reasons for increasing ocean transports through the Barents Sea opening. Today, the relatively warm and salty waters, that originate for the Atlantic Ocean, have an increasing impact on the Barents Sea (the so called Atlantification process), which leads to sea ice loss and potentially irreversible and amplifying ecosystem changes. To understand the origin of this trend, we reconstruct the BSO ocean transports based on wind time series over the Nordic Seas using deep learning.

Please refer to the respective publication: https://doi.org/10.1029/2024JC021663

A new model is born

Ulrike Löptien — Mon, 25 Mar 2024 20:18:38 +0000

Within the framework of the BMBF-funded project PrimePrevention we currently develop an ultra-high resolution model setup for the Kiel Bight (Baltic Sea). The new model setup will be named MOMKI. We look forward to the results of the first test simulations!

Ambiguous controls on simulated diazotrophs in the world oceans

Ulrike Löptien — Tue, 25 Oct 2022 10:39:31 +0000

Nitrogen fixers, are microorganisms that fix nitrogen from the air, making it available for ecosystems. It is known that they grow rather slowly so that they are easily taken advantage of by fast-growing algae – unless there is a lack of bioavailable nitrogen. This is when their unique property of “fixing” the nitrogen from the air comes into play. Surprisingly, nitrogen fixers in the ocean often fix more nitrogen than they need themselves – a property that still puzzles researchers, because it ultimately reduces their typical habitats, which are characterized by a lack of bioavailable nitrogen. The novel study, recently published in the Journal Nature Scientific Reports examines other more complex regulatory mechanisms that can give diazotrophs advantages. A series of model simulations illustrates the potential importance of predators and different nutrient limitations. This illustrates considerable uncertainties (up to sign changes) in projections of nitrogen fixation.

Press release on Baltic cyanobacteria

Ulrike Löptien — Wed, 10 Aug 2022 20:49:43 +0000

The press release by KMS (Kiel Marine Science) of our nature scientific report publication on Baltic Sea cyanobacteria blooms triggered a great interest by many newspapers and the NDR television. A German summary of is still available.

Cyanobacteria blooms in the Baltic Sea

Ulrike Löptien — Fri, 29 Jul 2022 11:56:17 +0000

Blue-green algae (or cyanobacteria) form regularly massive blooms in the Baltic Sea – especially in late summer. The bacteria can produce toxins and add bioavailable nitrogen fixed from the atmosphere to the already over-fertilized system. In the presented study, high-resolution model data from the Baltic Sea were combined with various observations. Simulated currents were used to trace the origin of blooms and to analyze water properties during bloom formation. The results of the study are surprising in that the blooms develop in the open Baltic Sea instead of, as might be expected, near the coast. This indicates that complex interactions between the different phytoplankton species may be at play and that hypotheses about simple direct relationships to the nutrient composition of the seawater should be considered with some caution.

Collaboration on the Arctic Ocean

Ulrike Löptien — Thu, 10 Feb 2022 21:07:14 +0000

We developed a collaboration with the Norwegian Institute of Marine Research on the Arctic Ocean. Our joint publication is now available: https://doi.org/10.1029/2021JC01727