Atlantic Water Transformation Along Its Poleward Pathway Across the Nordic Seas

Abstract

The warm and salty Atlantic Water is substantially modified along its poleward transit across the Nordic Seas, where it reaches deeper isopycnals. In particular, the Lofoten Basin, exposed to intense air-sea interactions, plays a crucial role in the transformation of Atlantic Water. Averaged over a seasonal cycle, Atlantic Water releases approximately 80 W/m 2 of heat to the atmosphere over a large area, leading to winter mixed layer depths of up to 500 m (locally exceeding 1,000 m in the Lofoten Basin Eddy, a permanent vortex located in the basin center) and substantial water mass transformation. We investigate spiciness injection (temperature and salinity increase) by winter mixing, by performing an isopycnal analysis using a comprehensive observational data set covering the

Mean Structure and Seasonality of the Norwegian Atlantic Front Current Along the Mohn Ridge From Repeated Glider Transects

“…As captured by the satellite image in May 2016, the surface temperature across the PF decreased from about 6 to 1 °C through a succession of fronts influenced by mesoscale features (Figure b), similar to the PF structure described along the Knipovitch Ridge by van Aken et al (). Higher salinities (about 35.3 g kg −1 ) were observed on the warm side of the front (Figure c), with a freshening trend consistent with recent observations (Bosse et al, ; Mork et al, ). The salinity on the cold side was more variable and reached minimum values from October to March.…”

“…The NwAFC is the western branch and follows the 2,000-m isobath along the Vøring Plateau and then the Mohn and the Knipovich ridges farther north (Orvik & Niiler, 2002) (see Figure 1a and supporting information Figure S1 for a detailed bathymetric map of the Mohn Ridge region), before it partly joins the Fram Strait branch and recirculates into the Greenland Sea. Along their poleward pathway, the slope and frontal branches exchange waters (Rossby et al, 2009) and a slab of AW fills the Lofoten Basin (LB), forming the largest heat and salt reservoir of the Nordic Seas (Björk et al, 2001;Bosse et al, 2018;Mork et al, 2014; see Figure S2).…”

Lateral Heat Transport in the Lofoten Basin: Near‐Surface Pathways and Subsurface Exchange

“…The Nordic Seas (the Norwegian, Iceland, and Greenland Seas) are a key region for the northward‐flowing warm water masses from the North Atlantic Ocean toward the Arctic Ocean (Rossby et al, ; Segtnan et al, ). In this study, we focus on the Lofoten Basin (LB) of the Norwegian Sea, an area of importance for the heat transport of the northward‐flowing Norwegian Atlantic Current (NwAC) (Bosse et al, ; Isachsen, ; Köhl, ; Raj et al, ; Volkov et al, ). At the Vøring Plateau, the NwAC splits into an eastern and western branch (Figure ), each transporting warm water toward higher latitudes.…”

“…The LB is a major heat reservoir in the Nordic Seas (Nilsen & Falck, ), manifested in the satellite sea surface temperature imagery (Koszalka et al, ), showing a warm wedge of water between the NwAC branches. Pooling of the warm Atlantic Water (AW) creates large buoyancy losses (Richards & Straneo, ), giving rise to convection and deep mixed layers (Bosse et al, ; Raj et al, ). Deep‐reaching winter convection and vertical mixing in the western part of the LB substantially modifies the AW (Bosse et al, ).…”

“…Pooling of the warm Atlantic Water (AW) creates large buoyancy losses (Richards & Straneo, ), giving rise to convection and deep mixed layers (Bosse et al, ; Raj et al, ). Deep‐reaching winter convection and vertical mixing in the western part of the LB substantially modifies the AW (Bosse et al, ).…”