TY - JOUR

T1 - Role of Greenland Freshwater Anomaly in the Recent Freshening of the Subpolar North Atlantic

AU - Dukhovskoy, D. S.

AU - Yashayaev, I.

AU - Proshutinsky, A.

AU - Bamber, J. L.

AU - Bashmachnikov, I. L.

AU - Chassignet, E. P.

AU - Lee, C. M.

AU - Tedstone, A. J.

PY - 2019/5

Y1 - 2019/5

N2 - The cumulative Greenland freshwater flux anomaly has exceeded 5,000 km3 since the 1990s. The volume of this surplus freshwater is expected to cause substantial freshening in the North Atlantic. Analysis of hydrographic observations in the subpolar seas reveals freshening signals in the 2010s. The sources of this freshening are yet to be determined. In this study, the relationship between the surplus Greenland freshwater flux and this freshening is tested by analyzing the propagation of the Greenland freshwater anomaly and its impact on salinity in the subpolar North Atlantic based on observational data and numerical experiments with and without the Greenland runoff. A passive tracer is continuously released during the simulations at freshwater sources along the coast of Greenland to track the Greenland freshwater anomaly. Tracer budget analysis shows that 44% of the volume of the Greenland freshwater anomaly is retained in the subpolar North Atlantic by the end of the simulation. This volume is sufficient to cause strong freshening in the subpolar seas if it stays in the upper 50–100 m. However, in the model the anomaly is mixed down to several hundred meters of the water column resulting in smaller magnitudes of freshening compared to the observations. Therefore, the simulations suggest that the accelerated Greenland melting would not be sufficient to cause the observed freshening in the subpolar seas and other sources of freshwater have contributed to the freshening. Impacts on salinity in the subpolar seas of the freshwater transport through Fram Strait and precipitation are discussed.

AB - The cumulative Greenland freshwater flux anomaly has exceeded 5,000 km3 since the 1990s. The volume of this surplus freshwater is expected to cause substantial freshening in the North Atlantic. Analysis of hydrographic observations in the subpolar seas reveals freshening signals in the 2010s. The sources of this freshening are yet to be determined. In this study, the relationship between the surplus Greenland freshwater flux and this freshening is tested by analyzing the propagation of the Greenland freshwater anomaly and its impact on salinity in the subpolar North Atlantic based on observational data and numerical experiments with and without the Greenland runoff. A passive tracer is continuously released during the simulations at freshwater sources along the coast of Greenland to track the Greenland freshwater anomaly. Tracer budget analysis shows that 44% of the volume of the Greenland freshwater anomaly is retained in the subpolar North Atlantic by the end of the simulation. This volume is sufficient to cause strong freshening in the subpolar seas if it stays in the upper 50–100 m. However, in the model the anomaly is mixed down to several hundred meters of the water column resulting in smaller magnitudes of freshening compared to the observations. Therefore, the simulations suggest that the accelerated Greenland melting would not be sufficient to cause the observed freshening in the subpolar seas and other sources of freshwater have contributed to the freshening. Impacts on salinity in the subpolar seas of the freshwater transport through Fram Strait and precipitation are discussed.

KW - ARCTIC-OCEAN

KW - CLIMATE

KW - EDDY KINETIC-ENERGY

KW - FLUX

KW - GLOBAL OCEAN

KW - Greenland ice sheet melting

KW - ICE

KW - LABRADOR SEA

KW - MODEL

KW - THERMOHALINE CIRCULATION

KW - VARIABILITY

KW - freshwater anomaly

KW - freshwater budget

KW - passive tracer numerical experiment

KW - subpolar North Atlantic

KW - subpolar gyre

UR - http://www.scopus.com/inward/record.url?scp=85066883753&partnerID=8YFLogxK

U2 - 10.1029/2018JC014686

DO - 10.1029/2018JC014686

M3 - Article

C2 - 31341755

AN - SCOPUS:85066883753

VL - 124

SP - 3333

EP - 3360

JO - Journal of Geophysical Research: Biogeosciences

JF - Journal of Geophysical Research: Biogeosciences

SN - 0148-0227

IS - 5

ER -