Science would not have progressed without the tenacity and sacrifice of many dedicated scientists, among who some go on to be unnoticed and unremembered. Scientists in this category include physicists, earth scientists, and meteorologists. The fields of meteorology and oceanography, for example, evolved from basic observations and were developed by gifted scientists into physically based theories that currently serve as foundations for these disciplines. In particular, synoptic meteorology greatly benefited from the weather map analyses of Vilhelm Bjerknes, which served as the observational basis for transforming the Norwegian cyclone model. These midlatitude cyclones are formed along the polar front, a surface separating cold polar air and warm subtropical air, a feature that was further examined by Gustav Rossby and Francis Reichelderfer. In this context, Rossby considered the link between upper-air movements, surface fronts, and ensuing downstream cyclone development. In particular, Rossby was interested in the large-scale features embedding synoptic systems, which partly inspired him to develop the theoretical concept of what is now referred to as Rossby waves. It is relevant to mention here that Bjerknes and Rossby’s investigations were essential for Jule Charney and Arnt Eliassen’s groundbreaking development of the quasi-geostrophic models of the atmosphere and the oceanic circulation, which served as the basis for the first model-based weather predictions.

These great pioneering meteorologists opened the gate of scientific-based advance in meteorology by training students and young scientific researchers and fostering them to carry forward the knowledge’s flame and enlighten the road to the following generations. One student from this early generation was Chester Newton, who became a recognized expert in synoptic meteorology. Newton was mentored and advised by Gustav Rossby and Erik Palmen. Initially, Newton worked with Rossby at the University of Chicago and then later also at the International Meteorological Institute (IMI) of Stockholm University. In his early research, Newton was inspired by Rossby’s idea regarding the three-dimensional structure of the polar front and synoptic scale features, including the jet stream, which serves as a key factor linking upper-level Rossby waves and surface fronts.

We consider upwelling and downwelling dynamics in an idealized ocean model configuration of the Western Gotland Basin in the Baltic Sea, featuring a gently sloping bottom in the west and a steep bathymetry in the east. Typical transient wind conditions and seasonally variable stratification are examined. Upwelling and downwelling jets develop at the coastal boundaries and interact through cross-shore boundary-layer flows. Initial evolution of the coastal jets is consistent with linear theory. The front position and the onset of instability is governed by the wind forcing, with a weak dependence on seasonal stratification. The unstable growth rates and wavelengths over the slope depend on the relative orientation of the slope and isopycnals, consistent with theory. The upwelling jets become baroclinically unstable during the wind-forced phase, whereas instability onset for downwelling on the slope is after 2–3 weeks (during the relaxation phase). The downwelling on the steep side is consistently stable. The regime with unstable upwelling on the slope side with concurrent stable downwelling on the steep side is more frequent (southwesterly winds: 30% occurrence) and leads to strong cross-shore transport. Unstable downwelling on the slope with upwelling on the steep side is a rarer event (northwesterly winds: 10% occurrence) and generates strong vertical mixing on the slope, with implications for oxygen and nutrient fluxes on the inner shelf along the Swedish coast. Baroclinic eddies contribute to elevated vertical mixing in the surface layer.

Ocean-driven submarine basal melt of the Greenland Ice Sheet remains a major source of uncertainty in climate projections of future sea level rise based on ice sheet modeling. State-of-the-art parameterizations focus on the properties of the ocean water reaching the marine-terminating glaciers, processes at the ice-ocean interface and subglacial discharge to estimate submarine basal melt. This study uses 2-dimensional, nonrotating, high-resolution ocean simulations complemented by theory and observations to quantify two effects of fjord bathymetry (sills) on the thermal forcing with consequences for the basal melt. These effects are the recirculation (reflux) of glacially modified water due to hydraulic control at the sill (which we study in detail) and the cooling of the inflow due to the restriction of the deepest and warmest Atlantic water inflow. For a fixed sill depth, an increase in subglacial discharge can make the exchange flow hydraulically controlled. Our results suggest that basal melt parameterizations should account for fjord bathymetry, and outline a road map to guide future parameterization developments relevant to narrow fjords.

Submarine glacier melt rates of the Greenland Ice Sheet remain a major uncertainty in climate model projections of future sea level rise. Development of submarine melt parameterizations have to a high degree relied on ocean circulation modelling of glacial fjords, designed to quantify effects such as ocean thermal forcing and fjordglacier geometry. Greenlandic fjords are relatively narrow, and it is frequently assumed that across-fjord flow variations are small enough to allow marine melt to be quantified with two-dimensional ocean–circulation models. Here, we present three–dimensional model simulations showing that the interplay between fjord–glacier geometry, side wall friction, and Earth’s rotation makes the circulation in ice–shelf cavities three–dimensional even in narrow fjords. Remarkably, we find that Earth’s rotation changes the flow pattern in the cavity below the ice shelf leading to a decrease in the marine melt on a 10 km wide ice shelf by a factor of five compared to a non–rotating simulation. Our study prompts using three–dimensional model configurations of Greenlandic fjords.

The northern sector of the Greenland Ice Sheet contains some of the ice sheet's last remaining glaciers with floating ice tongues. One of these glaciers is Ryder Glacier, which has been relatively stable in recent decades, in contrast to the neighbouring Petermann and C.H. Ostenfeld glaciers. Understanding Ryder Glacier's future behaviour is important as ice-tongue loss could lead to acceleration and increased ice discharge. Meanwhile, it is unclear whether Greenland-wide modelling attempts are able to accurately resolve the influence of fjord and bedrock topography and small-scale variations in ice dynamics for a glacier like Ryder. To fill these gaps, here we conduct targeted high-resolution modelling of Ryder Glacier until the year 2300. We find that mass loss is dominated by discharge under a low-emissions scenario all the way to 2300, leading to a sea level contribution of between 0.8 and 2 mm depending on the amount of ocean warming. Discharge also plays a key role under a high-emissions scenario up until 2100, after which a strongly negative surface mass balance becomes the dominant driver of mass loss. This negative surface mass balance leads to a much higher sea level rise contribution by 2300 of between 44 and 52 mm, with little sensitivity to the range of ocean warming scenarios used in this study.

The Greenland Ice Sheet's negative mass balance is driven by a sensitivity to a warming atmosphere and ocean. The fidelity of ice-sheet models in accounting for ice–ocean interaction is inherently uncertain and often constrained against recent fluctuations in the ice-sheet margin from the previous decades. The geological record can be used to contextualise ice-sheet mass loss and understand the drivers of changes at the marine margin across climatic shifts and previous extended warm periods, aiding our understanding of future ice-sheet behaviour. Here, we use the Ice-sheet and Sea-level System Model (ISSM) to explore the Holocene evolution of Ryder Glacier draining into Sherard Osborn Fjord, North Greenland. Our modelling results are constrained with terrestrial reconstructions of the paleo-ice-sheet margin and an extensive marine sediment record from Sherard Osborn Fjord that details ice dynamics over the past 12.5 ka years. By employing a consistent mesh resolution of <1 km at the ice–ocean boundary, we assess the importance of atmospheric and oceanic changes to Ryder Glacier's Holocene behaviour. Our simulations show that the initial retreat of the ice margin after the Younger Dryas cold period was driven by a warming climate and the resulting fluctuations in surface mass balance. Changing atmospheric conditions remain the first-order control in the timing of ice retreat during the Holocene. We find ice–ocean interactions become increasingly fundamental to Ryder's retreat in the mid-Holocene, with higher-than-contemporary melt rates required to force grounding line retreat and capture the collapse of the ice tongue during the Holocene Thermal Maximum. Regrowth of the tongue during the neoglacial cooling of the late Holocene is necessary to advance the terrestrial and marine margins of the glacier. Our results stress the importance of accurately resolving the ice–ocean interface in modelling efforts over centennial and millennial timescales, in particular the role of floating ice tongues and submarine melt, and provide vital analogies for the future evolution of Ryder in a warming climate.

The inflow of warm waters into the Nordic Seas, crucial for sustaining the climate-regulating Atlantic overturning circulation, can be reconstructed from hydrography using a north-south dynamic height gradient across the Greenland-Scotland Ridge. Variations in this influx are herein linked to northward-propagating thermohaline anomalies, initially observed at the intergyre boundary and likely driven by changes in ocean heat transport. As these anomalies reach the eastern subpolar North Atlantic, they modulate the cross-ridge dynamic height difference, thereby influencing both the Atlantic inflow and the Nordic Seas overflows on multi-year to decadal scales. Thus, these thermohaline anomalies play a dynamically active role in modulating the watermass exchanges across the ridge and downstream along the Atlantic Water path, rather than being a simple passive train of signals. This explains why these thermohaline signals are a key source of climate predictability and provides fresh insights into the functioning of the Nordic Seas overturning circulation from observations.

As the number of in situ measurements of ocean currents in the central Arctic Ocean remains very limited, much of our understanding of the Arctic Ocean circulation is based on idealized wind-driven models. In this paper, we make use of the latest available hydrography and Mean Dynamic Topography to study the Arctic Ocean time-mean circulation. Key concepts such as to what degree the flow is steered by bathymetry, equivalent barotropic, and consistent in direction along isobaths are evaluated. Comparing along- and cross-isobath velocities, we find that while the former generally has a larger magnitude, they are locally comparable in many regions. In these regions, the estimated cross-isobath velocities imply vertical velocities that can be orders of magnitude larger than typical surface Ekman pumping velocities. Even so, we find that the surface and bottom flow is generally well-aligned along closed ambient potential vorticity contours spanning local basins as well as the entire Arctic Ocean. In some regions of the central Arctic Ocean, where the hydrographic coverage is relatively sparse, bathymetric alignment is stronger in the surface. Despite this, our results suggest that the circulation is essentially equivalent barotropic and even barotropic in some regions. At some locations where water enters or exits the deep Arctic Basin, along-isobath flow reversals are observed at the surface as well as the bottom. Finally, the direction and magnitude of the bottom flow in regions of anti-cyclonic surface circulation are found to be sensitive to the choice of data set.

The Arctic Ocean is a key component of Earth's climate system, and an understanding of ocean dynamics in this region is central for predicting how the Arctic is responding to a changing climate. In this study, we examine the ocean circulation in a high-resolution numerical model of the Arctic Ocean and Nordic Seas. Based on what is observed in this simulation, we reexamine an existing idealized linear model estimating the time-variable large-scale circulation in ocean basins, and test it against the highly nonlinear numerical model. The idealized model is an integral relation derived from the linear momentum equations and assumes that the circulation around a closed depth contour is driven by surface stresses and regulated by bottom friction. We show that the idealized model estimates agree very well with the numerical simulations. This indicates that much of the variability of the large-scale circulation can be explained by linear processes. In particular, a correct description of the net surface stress over partially ice-covered areas improves the correlation between linear model and numerical simulations significantly in the Arctic Ocean compared to a previous study. However, undetected in that previous study, we now find that the linear model might be lacking a cyclonic tendency.

We study the impacts of a continental slope on instability and mesoscale eddy fluxes in idealized 3-layer numerical model simulations. The simulations are inspired by and mimic the situation in the Arctic Ocean's Beaufort Gyre, where anti-cyclonic winds drive anti-cyclonic currents that are guided by the continental slope. The forcing and currents are retrograde with respect to topographic Rossby waves. The focus of the analysis is on eddy potential vorticity (PV) fluxes and eddy-mean flow interactions under the Transformed Eulerian Mean framework. Eddy lateral vorticity fluxes dominate over the continental slope where eddy form stress, that is, vertical momentum flux, is suppressed due to the topographic PV gradient. The diagnosis also shows that while eddy momentum fluxes are up-gradient over parts of the slope, the total quasi-geostrophic PV flux is down-gradient everywhere. We then calculate the linearly unstable modes of the time-mean state and find that the most unstable mode contains several key features of the observed finite-amplitude fluxes over the slope, including down-gradient PV fluxes. When accounting for additional unstable modes, more qualitative features of the observed eddy fluxes in the numerical model are reproduced.