Depictions of Arctic Basin Circulation from two Mesoscale Ocean/Sea-ice Models
Abstract
Accelerated warming in the Arctic over past decades has resulted in enhanced sea-ice loss. In the Eurasian Basin (EB), in addition to sea-ice loss arising from atmospheric warming and feedbacks, increasing upward heat flux from wintertime convective mixing of warm sub-surface waters of Atlantic origin into Arctic surface waters is increasing, inhibiting sea-ice growth. Two forced mesoscale-resolving ocean/sea-ice simulations are used to examine ocean/sea-ice interactions, in particular the role of Atlantic Water (AW) in the EB for the near-present (2017-2020). One model is Pan-Arctic 1/25-degree Hybrid Coordinate Ocean Model (HYCOM) coupled to CICE5 (04HYCICE) and the other is the Parallel Ocean Program 2 (POP2) coupled to CICE5 on an ultra-high resolution global grid (8 km at theequator to 2 km at the poles - UH8to2). Both models were initialized from ocean/sea-ice states taken from the 1/25-degree Global Ocean Forecasting System 3.5 (GOFS3.5) and were then forced with the Japanese 55-year Atmospheric Reanalysis (JRA55-do).The overarching goal of the proposed work is to further analyze the two forced mesoscale ocean/sea-ice models and data assimilative GOFS3.5 to document a surge of AW in 2017-2018 into the eastern EB. This AW pulse is characterized by strong subsurface mesoscale eddy activity. Further, it is proposed to explore the role of subsurface (halocline) anticyclonic eddies in linking surging AW to surface waters andlocal sea-ice variability. First, maps of the mean AW layer circulation and associated eddy kinetic energy will be constructed on ayear-to-year and seasonal basis to understand whether AW layer characteristics in the EB are robust across the three simulations. Next, we will expand on earlier analyses and carry out further metrics of upper-ocean property structure in the EB for 2017-2020. To understand how these quantities vary across the eastern EB and during the evolution of the AW pulse, time series of mixed layer depth and area-averaged stratification will be obtained. Finally, to quantify the change in the amount of heat entering the mixed layer due to ocean processes acting both horizontally and vertically in the eastern EB, we will calculate the residual between the change in ocean heat content of the mixed layer for a particular month (one in fall and one in winter) between successive years and the integrated net surface heat flux anomaly over the intervening months. The mixed layer calculation will be carried out in a closed region (e.g., a box) encompassing the area above the sub-surface eddy-rich field in the EB to isolate the contribution from AW heat. In this manner, we can track year-to-year changes in ocean heat content in the mixed layer in the eastern EB as the AW pulse grows and decays and relate them to sea-ice variability.This study will contribute to the advancement of the state of Arctic Ocean modeling asit provides a means to explore emerging upper-ocean/sea-ice interaction processes associated with the Atlantification of the Arcticwhen mesoscale ocean eddies and processes are present. In particular, this study will provide an understanding of the evolution of a pulse of eddy-rich AW penetrating into the eastern EB and its interactions with surface waters and sea-ice in this basin. Understanding the representation of these recent changes in the Navy Arctic forecasting system is important to national security as new sea-lanes emerge as a result of declining sea-ice cover.Approved for public release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 08, 2024
- Source ID
- N000142412541
Entities
People
- Julie L. McClean
Organizations
- Office of Naval Research
- United States Navy
- University of California, San Diego