Freshwater composition of the waters off southeast Greenland and their link to the Arctic Ocean

David A Sutherland,E Peter Jones,Kumiko Azetsu‐Scott,A Jane Eert,Jón Ólafsson,Robert S Pickart

doi:10.1029/2008jc004808

Abstract

The freshwater composition of waters on the southeast Greenland shelf and slope are described using a set of high‐resolution transects occupied in summer 2004, which included hydrographic, velocity, nutrient, and chemical tracer measurements. The nutrient and tracer data are used to quantify the fractions of Pacific Water, sea ice melt, and meteoric water present in the upper layers of the East Greenland Current (EGC) and East Greenland Coastal Current (EGCC). The EGC/EGCC system dominates the circulation of this region and strongly influences the observed distribution of the three freshwater types. Sea ice melt and meteoric water fractions are surface intensified, reflecting their sources, and generally increase southward from Denmark Strait to Cape Farewell, as well as shoreward. Significant fractions of Pacific Water are found in the subsurface layers of the EGCC, supporting the idea that this inner shelf branch is directly linked to the EGC and thus to the Arctic Ocean. A set of historical sections is examined to investigate the variability of Pacific Water content in the EGC and EGCC from 1984 to 2004 in the vicinity of Denmark Strait. The fraction of Pacific Water increased substantially in the late 1990s and subsequently declined to low levels in 2002 and 2004, mirroring the reduction in Pacific Water content reported previously at Fram Strait. This variability is found to correlate significantly with the Arctic Oscillation index, lagged by 9 years, suggesting that the Arctic Ocean circulation patterns bring varying amounts of Pacific Water to the North Atlantic via the EGC/EGCC.

Highlights

[1] The freshwater composition of waters on the southeast Greenland shelf and slope are described using a set of high-resolution transects occupied in summer 2004, which included hydrographic, velocity, nutrient, and chemical tracer measurements
[3] The majority of observations to date of the East Greenland Coastal Current (EGCC) are from the summer months, which has limited our understanding of its seasonality and its relationship to the East Greenland Current (EGC)
We focus on the distribution of Pacific Water in the JR105 sections first, followed by a discussion of the presence of sea ice melt and meteoric water

Summary

Introduction

[2] Low-salinity waters exit the Arctic Ocean in two locations: through the west side of Fram Strait in the East Greenland Current (EGC), and through several small channels and straits of the Canadian Arctic Archipelago. Recent observations along the southeast coast of Greenland have revealed a separate branch of the EGC called the East Greenland Coastal Current, EGCC [Bacon et al, 2002; Sutherland and Pickart, 2008], which is located inshore of the shelfbreak and advects freshwater equatorward After examining the EGCC using data from the summer 2004 survey noted above, a compilation of historical hydrographic/tracer sections from the vicinity of Denmark Strait are analyzed to investigate interannual variation of Pacific Water content in the EGC/EGCC from 1984 to 2004. This is subsequently interpreted in light of shifting patterns in the AO

Data and Methods

Sœmundsson

Findings

Conclusions and Summary